Problems with Heartworm Treatment

The perfect treatment for a disease needs to satisfy several requirements:  the treatment should be 100% effective and it should be completely safe for the patient.  If it were also easy to do, and inexpensive, that would be perfect.  When the standard treatment for a disease fails to satisfy all four of those requirements, people begin to look for alternatives.  Sometimes this results in better treatments.  Sometimes it results in the patient receiving no effective treatment because he’s busy getting some quack remedy that does nothing at all (or kills him.  Remember Laetrile?).

Treating a dog to clear him of heartworms is a situation where the state of the art is not perfect.  Prevention of the disease with monthly preventive medicine has been effective most of the time.  Treating the dog who has adult, foot-long worms in his heart — that’s a different story.

Worms_in_heart2 The conventional view is that the worms are in the right ventricle of the heart, and the big pulmonary artery trunk.  If you do a post-mortem on a dog who has died from heartworms, you’ll find a lot of them there.  In a dog with a lower worm burden, there are not so many worms in the heart.

Worms_in_arteries_2 Most of the worms will actually be in the pulmonary arteries (taking blood from the right side of the heart to the lungs to get oxygen).  There may not be any worms in the heart.  If you open this dog at post-mortem, even though there may not be huge numbers of worms, you can cut the lung way out at the edge and find worms in the blood vessels.

The worms don’t eat the heart or arteries, they just float.  When there are so many worms present that they clog the outflow from the heart (like roots in a pipe), the heart wears out (prematurely) from the constant overwork of pushing blood through the clog. 

Worms_clog_artery2 Actually the worms don’t just float — they swim upstream. If they just floated, the pressure in the artery would force them downstream until they hit a branch too small to pass.  This would clog the artery either partially or completely, resulting in poor circulation to the downstream area of lung.  The dog might get a secondary pneumonia in this damaged area.  If he ran hard, increasing heart rate and blood pressure, the damaged artery could blow out, hemorrhaging into the lungs.  Indeed this does happen in some dogs, though most infected dogs develop the less dramatic signs of congestive heart failure: weight loss, coughing (especially after exercise), labored breathing, fainting spells and so forth.

This is ALWAYS what happens when the dog is treated to kill the heartworms.  Worms who have been swimming upstream, keeping the artery open, float downstream and clog up the works.  Unlike an intestinal worm infection (hookworms, roundworms, tapeworms, etc.), there’s no exit here.  With intestinal worms, you kill the worms and they leave the body with the next bowel movement.  With heartworms, they clog up the works like a blood clot would (except that few blood clots are a foot long).  You’ve heard that you shouldn’t get an air-bubble injected — how about a handful of foot-long worms?  The only way to get rid of them is to let the body’s microscopic white blood cell defenders eat them.  They’ll do it, but it’s a slow process, like termites eating your house.  It takes weeks after the death of the worms before the body dissolves them out of the circulation and opens all those clogs.

This is the unsatisfactory part of the heartworm treatment.  It’s why dogs feel bad a week or so after they are treated.  That’s when the worms die and shift position.  The dog may have a fever, cough, lose appetite, have trouble breathing, or cough up blood.  Sometimes you don’t see any of those things, but you can just tell that your dog doesn’t feel good.  You know your dog, and even though he may not have specific signs, you can tell when he doesn’t feel well.  This is the reason we ask you to restrict the dog’s activity for several weeks after treatment — no hard running for a while.

Most complications of treatment are minor and very treatable.  Severe problems like blood-vessel  rupture or allergic-shock-like reactions are extremely rare.  It could happen, but most dogs have years added to their lifespan when the heartworms are destroyed.

Here’s the crux of the matter, and the reason I’m writing today.  Ill effects during the heartworm treatment are related almost exclusively to the dead worms clogging up the pulmonary arteries.  The drug that’s used (Immiticide TM – melarsomine dihydrochloride) is unlikely to cause anything worse than some temporary soreness at the injection site.  It takes those little worms five days to die and they’re taking a  bath in it.  There just isn’t enough drug to bother the dog (unless he has some pre-existing severe liver disease).  That’s why it doesn’t matter whether your alternative remedy is a better chemical, a cheaper chemical, organic, holistic, homeopathic, herbal or black magic.  If it kills the worms, the arterial blood pressure is going to shoot them downstream and clog up the works.   

I’ve seen people use D-con rat poison, gunpowder, and levamisole (a sheep-wormer that is VERY hard on the dog’s liver).  Today a client brought in some misinformation he’d downloaded from some "Natural" website (with many products for sale).  Their nostrum is alleged to be superior because "There seems to be no risks of the parasites dislodging and creating vessel blockage."  Yeah?  Do the worms die or don’t they?  If they die, they’re going to move.  You may not have seen an artery pumping, but a two-millimeter artery will shoot three feet in the air if your clamp slips off before you get it tied.  Dead worms don’t swim – they go scooting downstream.

I wish that our standard heartworm treatment was 100% effective, safe, easy and inexpensive.  It doesn’t totally satisfy any of those criteria.  It is usually effective in eliminating all the worms, most dogs have no complications (or very minor and easily treatable ones), and it just takes two injections, 24 hours apart.  But, it’s not cheap.  And you have to let the body deal with those dead worms.  There’s just no way around that, no matter how you kill them.

P.S. Don’t forget to give your dog his heartworm preventive.

614 thoughts on “Problems with Heartworm Treatment

    • Christine Hogan says:

      Focus on the active ingredient. After a lot of research, I decided on ivermectin after much comparison. Extremely inexpensive drug that works great. I also requested the Rx for Heartgard because of the amount of active ingredient. My picky pup loves the treat form it comes in. I now purchase flea control and other wormer separately. This way I am certain that he is treated for heartworm. Was using Trifexis for 1 year when Dx with heartworms. Maybe vet HW test was negative because only juvenile in his heart. Positive blood test was 2 days after he took Trifexis and vet was stunned by the number of
      microfilarie (baby HW in larvae stage) that were in his blood. People who cannot afford the heartworm treatment use the slow kill method which involves ivermectin. It is also used on people, horses, and livestock. Needless to say, I believe the 3 in 1 convenience has put my loving pup through a lot of agony.

      • Doc says:

        Hello, Christine,
        In cases where we have seen apparent resistance to the preventives (dogs getting heartworms despite taking preventive), the medication with the fewest failures was Advantage Multi. When we were going through the three years of frequent lack of efficacy cases (2006 to 2009), we saw a similar percentage of failures in every other preventive. I had my own dog on Heartgard on the first, and Revolution on the 15th of every month, and she got heartworms anyway. Many coon-hunters in our area use the cattle injectable form of Ivermectin, giving more than 100 times the dose in Heartgard, and we saw some of those dogs get heartworms. The more current thinking on slow-kill uses a combination of Advantage Multi monthly and a month of oral doxycycline. There are reports of good efficacy, but I haven’t had any luck with it so far.
        At this point, in our area, we aren’t seeing lack of efficacy cases (unless people just are missing doses). However, this is still a big concern in the profession. I am participating in a research study collecting microfilariae from infected dogs for genetic analysis (I’m not doing research, just providing specimens). We are looking to document how much of a problem this continues to be.

    • Melissa says:

      So rest & inactivity. Is best after heartworm treatment in adult dogs that never been treated before if &if we start them right away on a heartworm med ? And it takes days to rid ?

      • Doc says:

        Hello, Melissa,
        We start the patient on a heartworm preventive medicine right away so that they don’t get any more heartworms than they already have. The treatment that kills the adult heartworms does NOT have any effect on preventing new infection from the mosquito bites.

        When the dog receives the melarsomine injections (Immiticide or Diroban), it takes several days for the worms to die. When they die, the blood flow carries them out into smaller arteries in the lungs, where they cause blockages. Activity should be restricted so that you don’t have a lot of pressure on those blockages. It takes 4 to 6 weeks for the white blood cells to destroy the dead worms and open the vessels.

  1. Dr. Mobley says:

    Dear Joanne,

    Thanks for reading. We really only have one option to treat adult heartworm infestations: Immiticide, made by Merial.

    For regular monthly prevention, there is milbemycin oxime and the avermectin family. Milbemycin is in Interceptor and Sentinel, made by Novartis. Ivermectin is in Heartgard 30 (made by Merial) and various generics, such as Iverhart. Selamectin is in Revolution, made by Pfizer, and applied topically.

    There are other products. These are the ones that I use to provide a variety to my clients. There is no one product that is best for everyone. Some give intestinal parasite control as well, so give flea control as well. Some are easier to administer for one dog, others for another. I believe them to be equally effective, so it’s a matter of what works best for you and your dog.

    • Debbie Lassiter says:

      Doc Mobley,
      Thanks for your easily understandable explanations. We rescued a small dachshund/Pomeranian that was living outside in NC, that unfortunately has heart worms. A seizure about a month after getting him precipitated an earlier than scheduled visit to the vet. He had a grade 4 heart murmur. He started on the protocol with doxy and steroids… his seizures persisted and required escalation in his seizure meds. After his first shot, he had a weird affect of being in a daze..and needing to walk..for about 12 hours straight. He has a lesser reaction like this after a seizure…lasting maybe 30 -60 minutes. A few days after that shot, he also began blistering. Oddly, it was not at the injection site itself..some were on his back, some were on his sides, some on his haunches. They were big and he subsequently lost all the hair in those areas. He recently had his 2nd/3rd injections..not as many blisters appeared, but there are 2 prominent patches. He has had a few more seizures in the last 2 weeks (since the shots) after being well controlled since doubling his dose. He is coughing more this time, but I see that is expected. My question to you after giving you this information is ..can he have worms in his brain that are causing him to seize and can he have worms in his tissues that the only exit upon dying is to blister?

      • Doc says:

        Hello, Debbie,
        This is certainly a complex case, due to the additional medical problems with the seizures.

        There are reports of adult heartworms being found in unusual locations, like the muscle of the diaphragm or the anterior chamber of the eye. These are highly unusual, however.

        I would consider that the skin situation might be a bizarre reaction to the drug, but it his highly unlikely that they are related to the presence of abnormally located heartworms.

        Without a C-T or MRI to rule out masses in the brain, we don’t really know the cause of the seizures. Many seizure patients have completely normal test results with C-T, MRI, EEG, spinal fluid analysis, everything. Only during their seizures do you see changes in the EEG (brain electrical activity). We don’t understand what causes these seizures. We used to call them epilepsy and now they are called idiopathic seizure disorder. We do not understand why they occur.

        I think it is unlikely that your dog has a worm in its brain, but you would need an MRI to rule that out.

        • Mindy says:

          Hi Doc. I don’t know how to start a new comment. I just read this article and another one about heart attacks in dogs. My dog was 7 or 8 years old. She was not taken care of well by her previous owners and since I recently graduated and got a job, I was able to take her under my care. She was a wild dog… Always running around, barking at everyone and everything she sees, hated to get her hair groomed. I took her to the vet because one of her eyes were swelling on and off… At the vet, they gave her all her vaccines, an antibiotic shot (Convenia I believe?), an antibiotic eye drops and allergy meds (hydroxyzine)… It was very difficult to give her the eye drops… They couldn’t even give it at the vet even with a muzzle on her. I managed to give her the eye drops but her eye still gets swollen now and then… I figured it was due to allergies. Anyways, she got her blood work done as well that day… and they told me she was heartworm positive… She was asymptomatic so they classified her HW stage at the lowest stage. And so reading up about heartworms, I knew she needed to get it treated and paid for her treatment.

          First they gave me a 30 day supply of doxycycline and a monthly HW prevention. After a few days of giving her the doxy, we noticed she wasn’t herself anymore. She was always tired, not eating, nauseas, vomiting up foam and liquid, and she was drinking a ton of water almost every day. I went to the vet to express my concerns but the vet (my first time seeing/talking to him, even after several visits) was very dismissive towards me… He told me she needs it anyways or she will die. I know she needs it but I was concerned for her. I even told him that I’m worried she will have a pulmonary embolism because she isn’t a calm dog, but he told me to just find a way and deal with it. I mentioned her age and he said he didn’t understand why I was bringing up her age. I had already paid for the treatment… I just wanted him to give me some reassurance and support.

          30 days passed and my dog got her first injection. She did not receive any prednisone or pain meds afterwards. That night she was shivering and I thought she was cold so I put a blanket on her (now I’m reading that dogs shiver when they are in pain)… not even a week after her first injection, she died. She screamed in her cage, she left her cage, and collapsed. I will never forget this image of her. She was convulsing or something too… She defecated on the floor. I tried CPR but I was scared… I didn’t know how to perform CPR on a dog… So I stopped… all while I was crying my eyes out. She defecated and later peed over the floor. She was gone. It’s been a month now but I am still devastated over her death.

          I tried my best to keep her calm, but she was never a calm dog. She had a cage but she didn’t like to be in it. We let roam in the kitchen (her cage is there too, there’s not a lot of room for her to run in the kitchen) that we gated up so she couldn’t run around the house. She usually just lays on the floor observing things. Well that day everything went wrong… and I will always blame myself for it.

          She sleeps in my room at night. I carry her up there. Sometimes she sleeps with me on my bed but that previous night, she slept in her corner that I gated up (I took the detachable gate from the kitchen). Usually I carry her down to pee/poop and bring the gate down with me too. That morning I had to drive a family member to the airport. My mom comes in my room to tell me to wake up and she let my dog out. I told my mom you have to carry her but she didn’t listen to me. She also didn’t bring the gate down and I didn’t notice because I was tired and had to rush to get ready to leave. When I came home, my dog was in her cage barking to be let out. We let her out to roam around the kitchen and I went upstairs to change. She ran upstairs to look for me because the other opening wasn’t gated. I monitored her but she wasn’t coughing or having any shortness of breath. She was normal… but hours later she died. The tech/manager at the vet’s office says it could have been a heart attack…

          I am truly devastated… she did not deserve this and I feel like I spent hundreds of dollars to accelerate her death. She was only about 7 or 8 years old. She had so many years left. It’s all my fault. I think about her everyday for the past month. I imagine scenarios in my head, all the “what-ifs”… I even wondered if she had any underlying heart conditions? The previous owner was a smoker but I’m not sure if smoking affects dogs the way it affects humans? When I hold her I feel her heart pounding in her chest. I’m not blaming my vet either, but I wish he was more understanding about her behavior… When she got her blood work done, they didn’t tell me if everything else was normal or not. When she got her x-ray, all they said was “yep the heartworms are still there.” I had to research all of it on my own, too, since they never explained anything to me. I just don’t know what to do and I don’t think I’ll ever move past this. I have depression and now this happens and I just don’t know anymore.

          • Richard says:

            I’m so sorry to read this. It sounds like the vet didn’t follow best practices. Sometimes that matters and sometimes that doesn’t matter. Send your vet a note in the hope it saves other lives. Don’t blame yourself and don’t think about things in the past you cannot change. You shared a great love with your dog that will last forever.

          • Doc says:

            Hello, Richard,
            I feel that the main deficiency in care was poor communication. It is a complex disease and a complex treatment. Sometimes we think that we have explained things very well, but we haven’t fully communicated. It can get worse when we get too busy. Often clients are embarrassed to ask more questions, and we don’t pick up on that.

          • Doc says:

            Hello, Mindy,

            Sorry I am so late in replying. I had a bug in my comments.

            The only problem I have ever seen with second-hand smoke was a dog who had a lot of coughing problems. I don’t think that is much of an issue here.

            In my experience, dogs inside a house have not done enough strenuous exercise to make complications more likely with the heartworm treatment.

            When the heartworms shift position after they die (usually 3 to 7 days after the treatment), they clog up the arteries downstream. This can cause a ruptured artery, with hemorrhage into the lungs. This can cause a reaction like someone who is allergic to a bee-sting, an allergic shock-like reaction.

            I can see how you feel responsible for causing your dog’s death prematurely. The other side of that coin is that the worms could have moved on their own at any time, causing a very similar situation. Then you would have felt responsible because you DIDN’T treat him.

            It’s a bad disease, and you had a bad situation. I am sorry for your loss, but I don’t think you should blame yourself.

          • Jennifer Saxe says:

            I am so sorry for everything you’ve gone through. I can not imagine. Please try to be gentler with yourself. You did everything you knew to do, and you were clearly doing your best to save your baby. I’m quite sure your dog you you loved her. I would definitely send your vet a message- bc he sounds horrible. You don’t sound horrible. You sound like a genuine caring human being who tried to save a dog. Please don’t let that take away from others who need help too. You are not a bad person. You are devastated bc you have a kind heart. I’m so sorry. I will keep you in my prayers. ????

          • Shauna Jones McDonald says:

            Your dogs in heaven and u will see ur dog again. My dog has heartworms too he’s been taking the doxy for like 3months ,I thb seems like a long time. It’s supposed to be a slow kill method. But our vet is very vague w me too. I’m srry ur going thru this . By dogs breathing is very labored. I’m really concerned about him. He’s 9yrs old my big baby. Contact back if can.

  2. Gina says:

    Have you ever heard of heartworm treatment affecting a dog’s behavior? We adopted a rescue dog a couple of months after he was treated for heartworm (he ended up losing an eye because the second dose wasn’t administered in the right timeframe) and we’re having some severe behavioral problems. Just wondering if this could be part of it.

  3. Doc says:

    Heartworm treatment generally causes problems in the lungs, via the damage to the blood vessels that supply them (the pulmonary arteries). The period of recovery while the worms are being dissolved can certainly be stressful for the dog. Generally speaking, I have not seen any changes in the dog’s personality and behavior after recovery.

    I would not be surprised if the dog were having trouble adjusting to the loss of an eye, but I am puzzled as to how this occurred. I have never heard (nor can I find in a search of Veterinary Information Network) of a similar situation. Ivermectin is generally used at the end of treatment to clear the baby heartworms from the bloodstream, and ivermectin toxicity is known to cause blindness, but this is usually in both eyes and is usually temporary. I have never seen this myself, but it is reported as a consequence of overdosing (or in a dog that is exceptionally sensitive to the drug).

    I would be interested in more information as to how the blindness developed.

  4. Mary Lee says:

    I have a 3 year old great dane that I recently rescued from a family that “didn’t have time to take care of him.” He is heartworm positive and I took him in to start his “Immiticide” treatment this past Monday 2/7/08, and was told if everything went well he should be able to come home on that Wednesday 2/9/08. Long story short: He is still not able to come home as of today 2/14/08. He has had a “very severe reaction to the injection” as in the injection site itself. My veterinarian says that he has never seen a dog react this severely before from the actual injection. His whole pelvic area is completely inflamed, his white blood cell count is extremely elevated, he is in sever pain and cannot even get up to go to the bathroom. I can’t even type this without crying. I feel like they are doing everything they know how to help him. They have him on an IV for fluids, a strong antibiotic they started today, and “tramadol” for pain. Any suggestions?

    • Sheri Schoonover says:

      My Chopper died and they had to resuscitate him…we then went to topical treatment…he was cleared today of heart worm after the 6months alternative protocol and he just died on us after he had his heartgard and nextgard

      • Doc says:

        Hello, Sheri,
        We know that sometimes the breakup of the dead worms can leave damaged areas in the arteries. These damaged arteries can break, bleeding into the lungs.

        The medications are not dangerous otherwise.

        Your own veterinarian may be able to give you a better insight into what happened.

        I am sorry for your loss.

        • M says:

          The chemical is dangerous to the dog. My little 2 year old rescue got massively sick and could not stop throwing up. She had to go back to the vet and be on fluids and receive zofran to stop the vomiting. She was treated for vomiting, dehydration and exhaustion for several days. She was so sick, I thought I was going to lose her. Now I am worried about her kidney function and we are off to the vet once again. Her poor little body has been beaten up by these treatments. I hope she makes it.

          • Doc says:

            Hello, M,
            I am sorry that your dog had such a bad experience. I have treated thousands of dogs without problems related to the drug itself. I can recall some severe local reactions to the injection. We had one patient with pre-existing liver disease who had a lot of difficulty with the medication. There is no medication that is 100% safe for every single patient. Some people can’t take an aspirin. I know that it is no consolation to you if it only happens one in a million times if your patient is that one. Your veterinarian will do everything possible to get her through this.

  5. Mary Lee says:

    Correction to recent post. My dates are messed up. I brought him in for treatment on Monday 2/4/08 and was supposed to be able to pick him up on 2/6/08. Today is 2/11/08.

    If they’re is any advice you may be able to give, I would greatly appreciate it. It seems that since it is uncommon for a dog to have such a severe reaction there is in turn limited info on it. This great dane named Duke is the most precious dog I have ever met. I am a huge dog lover in general but there is something extra special about him and I will do anything I can to help him. I love him very much.

    • Yesenia Rodriguez-Hower says:

      Hello. It’s now 2021. Is there an update on your dog? I’d love to hear that he pulled through and lived a wonderful and loving life.

    • Alison says:

      My dog just had a severe reaction to the injection as well. His entire spinal cord was inflamed leaving him in excruciating pain and paralyzed. They tried all the could for a week but he eventually got worse and we had to put him down. He was on three different pain meds and still uncomfortable and was given corticosteroids the entire week. I scoured the internet for any similar cases but there are just so few that have had this kind of reaction 🙁

      • Doc says:

        Hello, Allison,

        I cannot imagine such a severe reaction from the Immiticide. I guess it would be possible if somehow the needle was very close to where a spinal nerve comes out, but that would be super rare.

        I am sorry for your loss.

  6. Doc says:

    Hello, Mary,

    I am sure that your veterinarian has already called Merial (the maker of Immiticide) to report the reaction and ask for their advice.

    When Immiticide first became available in the U.S., Merial sent out mailings, including an instructional video on giving the injections. The injections are given deep in the epaxial muscles (the long loin muscles on either side of the spine), using a 1&1/2-inch long needle to deposit the medication deep in the tissues.

    I had been using the product for about a year when I had a similar experience to yours. A Rottweiler patient developed an open sore the size of a golf-ball at her injection site. When I called Merial, they asked if I had kept firm pressure on the injection site for two minutes. I had not. They then said, “You need to do that.”

    The medication is very caustic and needs to be distributed deep in the muscle fibers for absorption. There’s really no “place” for it to go — it just spreads between the muscle fibers to be picked up by the bloodstream. The easiest place for it to spread would be back up the needle track, allowing it to pool under the skin. This produced the bad reaction in my Rottweiler patient. The two minutes of pressure is to try to prevent this creep back up the needle track.

    I noted that there was no mention of this “pressure for two minutes thing” in their literature or video [and there STILL is not, and I have spoken personally with several veterinarians who have never heard of this]. They replied, “Yeah, we know, but you still need to do it.” Thus, all of my heartworm treatment patients since then have also received a “laying on of hands”, and I’ve had no further problems.

    That being said, everything may have been done as well as humanly possible and the dog is having an idiosyncratic reaction, like someone who just can’t take aspirin or something. It’s not the drug, it’s just him. As far as treating the problem is concerned, at this point the care is going to be mostly supportive, as it would be for a brown-recluse spider-bite that causes tissue to die and slough.

    Your doctor’s approach of Tramadol (a mild narcotic which is usually very helpful and well tolerated) and antibiotics (so that bacteria don’t get a chance to complicate the situation by invading the damaged tissue), both sound very appropriate. The only other thing I might be doing would be hot compresses three times daily to increase circulation to the area and speed healing. You might also ask about Lidocaine patches. These can be applied to the skin on either side and give a constant slow release of local anesthetic into the area to help control pain. NSAIDs like Rimadyl can be combined with Tramadol for additional pain relief. NSAIDs should not be used if the patient is already on some form of cortisone for inflammation.

    It sounds to me like your veterinarian is doing a good job in a difficult situation.

    I hope this information is helpful to you. Good luck and thanks for reading and writing.

    • Jill Chamberlain says:

      In addition to holding pressure after the injection, could they also apply using the z-track method? This helps prevent leakage into subcutaneous tissue. As a nurse, I have used this method many times.

      • Doc says:

        Hello, Jill,
        I think you could certainly do that, but the back-leakage is not usually a huge problem. The instructions with the medication just tell you to use a different needle for injection than the one that you used to fill the syringe. I had one really bad mess one time, and they recommended putting post-injection pressure in the future. I do it regularly, but only for about 20 seconds. I haven’t had any other sloughs in treating hundreds of dogs.

  7. Liz says:

    Butch is a rescued Malamute and golden lab. mix.He tested positive for heartworms and I was told if the worms were not stage 5 he could be treated. The tests were done and Butch was treated. He ended up with his salivary glands infected and severe pain. He went back for a stay at the vet and was sent home again and now we are being told that he has a blood clot and he is dying and the vet said we should put him down? Why would he have us go through with the treatment to tell us that? The dog has lost alot of weightand his equilibrium seems to be very bad, he can only walk so far without coughing and falling over. Help us Please.

    • Sherry BRYARS says:

      I was told the dog we found abandoned. Had a faint line and was positive for heart worms.I only see one line .Is the treatment the same??? As adult heart worms.

      • Doc says:

        Hello, Sherry,

        I am guessing from your post that this was one of the in-clinic heartworm antigen (adult heartworm protein) tests. These usually have two areas to view a color change, whether it is a spot or a line across the device. One would be the positive control, which should always change color to show that the test is working. The other would be the test area. Any color change here indicates the presence of the heartworm protein. This protein comes from the reproductive tract of adult female worms. We know that if there are fewer than four adult female worms, it can give a false negative. If there is a positive color change, this is pretty much a “yes or no” rather than a quantitative test (how many).

        While it is tempting to feel that a faint line means fewer worms and a dark line means more worms, this is not something that has a definite correlation.

        The test for baby worms (microfilariae) involves seeing them under the microscope. If you see babies, you know that there are adults present. Babies mean mommies and daddies. The baby heartworms transmitted by the mosquito are a different life stage and are not seen in our testing of the dogs.

        • mary says:

          I just rescued a 4.3lb, 3 year old female dog that is heartworm positive. After 30 days of doxy and 2 doses of prevention, we returned to the shelter for the adulticide injection. The vet there gave 2 injections over 2 days to start. Not the usual 1 shot and 30 day later 2 shots. Do you have a sense as to why they started with 2 shots?

          • Doc says:

            Hello, Mary,
            If they felt that the dog had a very small worm burden, then it might have made sense to just go ahead with the full treatment. It’s hard to quantify the worm burden, but if I had a 1 year old dog who hadn’t been outside much, maybe took preventive most of the time before he turned up positive, I might do the same thing. For the sake of argument, if you had 3 worms, what’s the difference between killing one this month and two next month, versus three right now? That’s an oversimplification. If I were you, I would just ask the doctor who is treating the dog.

  8. Doc says:

    As I mentioned in my posting, there is always a risk involved when you treat dogs for heartworms. There is simply is no way to guarantee success when you have foot-long worms clogging up the works. Most dogs do well, or survive minor complications, but some do not.

    I must confess that I cannot imagine how there could be any relationship between the heartworms and the salivary glands. There must be something lost in the translation here.

    I am sorry that things have gotten so bad, but I feel that your veterinarian acted in good faith to do what he felt was in the best interests of your dog and for you. Sometimes things just don’t work out the way we would wish for them to.

    Thanks for reading and writing.

    • Sandra Y says:

      Hi doc, my dog has recently tested positive for heartworms. He is already starting with the doxycycline, but I am really concerned and nervous when the time comes that less activity is to be observed. He is calm inside the house but everytime the doorbell rings, or he hears an unusual sound, other dog barking, he goes crazy and barks. He is asymptomatic and im afraid this will cause stroke or death when he starts his melasormine injections.and shorten his life instead of treating him. Do you have any advice or suggestions for this?

      • Doc says:

        Hello, Sandra,
        That type of increased activity is not likely to increase his risks of complications, in my experience. The dogs that have trouble with exercise are generally the ones who have prolonged aerobic exercise, running loose or being encouraged to play Frisbee for 20 minutes. Generally speaking, my patients seem to do fine if they are on a leash outside or confined to the indoors. Walking on a leash seems to be okay for most of them. I understand about these bursts of excitement, but I don’t think they are a big concern. If he truly goes nuts for a prolonged period of time, you might talk to your veterinarian about a sedative, like trazodone.

        • Kaylin H says:

          Hi doc. My dog just got his first shot of immiticide and the vet said he did great, he’s used to being in a crate 10 hours a day while we work he’s just adjusting to the extra hours before bed being crated as well. My question is, he sleeps with us at night is him jumping on and off the bed going to be a problem? Should we allow him to sleep with us? He’s leashed walked to relieve himself and throughout the day and evening will be in a crate I’m just concerned the jumping will be a problem or that he may roam around the bedroom while we’re sleeping

          • Doc says:

            Hello, Kaylin,
            I sincerely doubt that would be enough exertion to make any difference at all in your dog’s recovery.

  9. Cindy O'Neal says:

    My Golden has been on the heart prevenative medication “Heartgard” I have never missed a dose and she goes to the vet and is very well taken care of. Today, I took her and the other golden that I adopted to the vet. Red, checkup…and Maggies the adoptee to be spayed. An hour after dropping them off, they called to tell me that maggie had heartworms, and cancelled the spayed. We went to the vets office and then told that Red also was positive…and she has always been on heartgard. Then they told me that we would have to pay for Maggies the adoptee, but Red…Meril would pay for it since we have records of her being on heartgard monthly. What do we do now…these dogs are the world to us. Any advice please

  10. Doc says:

    I sympathize with your situation — more than you know. I’m going to have to post on this one at last, so look in on the blog pretty soon.

    The failure of the preventive medicines (ALL of them, not just Heartgard 30) to be 100% effective is becoming a problem. I am told it is primarily in the Mississippi valley, and gets worse as you go farther south.

    In the last two years, we have seen a ten-fold increase in this situation. The good news is that we are still seeing just a small percentage of dogs affected, and almost all are large breed, outside dogs. The other good news is that these dogs have very few heartworms present, as evidenced by the fact that none of them have had any significant side-effects of treatment.

    While there is no guarantee, the odds are overwhelmingly in your favor that your dogs will do well. Get them treated, send the bill to Merial, and get them spayed afterwards.

    Good luck, and thanks for reading and writing.

    • Jill says:

      I was told by my vet years ago that when purchasing prevention online and having it delivered by the post office, it is not always kept within the required temperature in the summer either when it is in the delivery truck or when in the mailbox. It may not be as effective if it gets too hot. It makes sense, so I purchase it from the vet.

      • Doc says:

        Hello, Jill,
        I don’t know how hot it would have to get. My suppliers never send it on ice and it gets pretty darn hot here in the summer. It is possible, so I have sent a communication to a clinical pharmacologist to try and get more meaningful data than my opinion.

    • Ellen LIbfeld says:

      I just started reading these comments and want to say thank you. My dog, now 16 months, has adult heartworm. He was rescued from Puerto Rico with his Mom and siblings when he was not quite 2 months old, went to a shelter, had a negative heartworm test, was adopted by another family, given Heartguard for two months. Then he returned to the shelter, had another negative heartworm test and we adopted him the next day. We have given him Simparica Trio every month like clockwork, and don’t understand how he has a positive antigen test for adult heartworm (no microfilaria). My dog is on doxycycline and will start shots next month. My vet doesn’t understand how this happened because of the two prior tests. Is something wrong with Simparica? He has never missed a dose of preventative care. The treatment, possible side effects, and costs are huge,; how can you keep a 16 month, VERY ACTIVE puppy quiet?

      • Doc says:

        Hello, Ellen,
        I think Simparica Trio is fine. With the history here, I suspect that there may be some gaps we will never know about.

        As far as keeping the puppy quiet, my experience has been that dogs who are in the house, walked on a leash, and have supervised quiet play in a small fenced yard are being quiet enough to not increase risks of complications. We try to avoid prolonged aerobic exercise. Dogs who escape and run for hours DO have an increased risk of complications. I do not feel it is necessary or desirable to crate the dog when people are present to supervise.

  11. Sam says:

    I am fostering (to adopt) a sweet little girl dog who was heartworm positive and has received the initial treatment (on the 21 and 23 of February). She and her 3 pups were deposited in a drop box in S. Carolina. The treatment was given at a clinic in N. Carolina, and the Vet’s guesstimate on her age is 1, I think maybe a little older, lots of tartar, but maybe that’s just a poor diet? Anyway she is young and probably had the pups about 8(?) weeks ago. She is definitely underweight, at about 20lbs. She seems happy enough and alert and not without energy, but is not hyperactive. I am trying to figure out how “quiet” she should be kept. Walks? Playing in the house? No activity? And for how long? I want to keep her mind engaged with training, etc… but don’t want to get her over-excited. Also, she is sneezing a lot. (not boogery sneezes, just dainty little ones, but a lot, usually after she’s been lying down) Does this mean anything re the heartworm, or is it more likely that it’s something in my house (she’s only been here for two days)? So glad I found your blog!

  12. Doc says:

    Hello, Sam,

    The sneezing is probably not related to the heartworm treatment. Consider feeding a good quality puppy food while you are trying to help her recuperate from poor nutrition and nursing babies.

    Activity should stop short of any prolonged aerobic exercise. Relaxed walking on a leash is okay, any normal mild play in the house is okay. We want to avoid any dramatic or sustained rise in heart rate and blood pressure. This would be more likely to shove chunks of dead worm farther into the arteries, creating a more complete blockage, increased pressure, and potential blow-out, bleeding into the lungs.

    It is not possible (nor desirable) for the dog to lie still for six weeks. Just make your best effort to avoid strenuous activity. Call your veterinarian if your dog shows signs of difficulty: coughing, difficulty breathing, poor appetite, fever, or just generally feeling bad.

    Thanks for reading and writing.

    • CBalencia says:

      My 7 year old Lab just had her heartworm treatment 6 days ago. She seems to be feeling okay except that she breathes heavy and pants when inside the house. She showed these actions before we found out she had heart worms. Is this normal? I called my vet about it and they said it was normal. As far as exercise restriction goes, she’s not playing but she does walk around the house every now and then. She breathes really hard while walking. Is this something to be alarmed by?

      • Doc says:

        Hello, CB,

        “Heavy breathing” and panting are subject to interpretation. I would recommend that you get video of the dog at rest and walking around the house so that your veterinarian can see what you are talking about.

        • S. S. says:

          I’d like to know about panting. Ours has had 1 shot. Due for other two shot in 2 weeks. She’s a large dog with panting. We decided to give her pain medication with her prednisone she Is already taking.

          • Doc says:

            Hello, S.S.,
            The panting could be due to pain. Be careful what you add in the way of pain medication. NSAIDs (Rimadyl, Carprofen, Metacam, Piroxicam, etc.) do not play well with corticosteroids. Over the counter NSAIDs like ibuprofen and Aleve (naproxen) cause stomach bleeding with one tablet and should be avoided in dogs. Check with your veterinarian about safe alternatives.

  13. paula b says:

    My foster dog who had heartworms was treated with Immitcide and was finally retested for heartworm and thankfully it was negative.
    She was adopted, the adopter was told of her HW treatments and that she still had a cough and wheezing if she got excited or ran while playing…My vet put her on prednizone 5 mg bid…and now says to up it to 10 mg. bid….the person who adopted her took her to his own vet…who told him to bring her back to us because she would have problems if not now..but down the road….he did no tests or anything…just from hearing that she had been treated for heartworms and was still coughing and wheezing some. I understand that it takes several weeks sometimes for the fluid and inflamation to go away and that is why you give them pred. I have to take her back because this guy’s vet scared him. Whose vet do you think is right? Mine or the adopter’s? I am so upset about all of this. I would appreciate an answer or advice asap.
    Thank you, Paula B

  14. Doc says:

    Hello, Paula,

    I would have to say that, generally speaking, the doctor who has actually examined the dog is in a better position to give an accurate assessment of the dog’s health.

    It is certainly true that the dog’s pulmonary arteries and lungs suffer damage from the presence of the worms, both while they are alive, and when they are killed and being phagocytized (dissolved away by the white blood cells). There may very well be permanent problems, in that the damage may prevent the dog from being athletic. However, even so, he may be able to lead a perfectly good quality of life.

    I would say it is possible for the dog to be chronically ill after recovering from heartworm treatment, but I would also say that it is not very common for that to be the case. Most dogs lead a good quality of life (even if not “100%”), and are NOT “perpetual patients”.

    For a more objective evaluation, one could radiograph the dog’s chest now and repeat the films in 30 days to see how the condition of the lungs progresses. I believe it is too soon to say what the dog’s eventual outcome will be.

    I hope this is helpful to you. Thanks for reading and writing.

  15. paula b says:

    Hello, thank you for such a quick answer. I do appreciate that.
    I picked Shyanne up today and have her back. She is happy acting…lively…certainly not depressed but is wheezing a lot. I am not sure if the adopter was giving her the pred like he was told or not. I just gave her 10 mg. of pred. Would your advice be to keep her on that twice a day until the wheezing stopped? Also, I have read about Doxycycline and she did not have that prior to the hw treatments nor during them…would it be a good idea in your opinion to start her on that?
    My vet, gets a little irritated with clients who get on the internet to read up on things like this. I guess she feels like if a client does this..that they don’t trust her judgement as a vet. I just want to educate myself as much as possible. I do realize though…that sometimes people who are not trained and have degrees in medicine can easily get confused and maybe even panic reading too much into something or not understanding it right.
    I read somewhere that if the dog’s gums are dark red there could be a secondary infection…so of course as soon as I got her back tonight…I looked at her gums…they do seem to look darkish red…not pink. Am I reading too much into this and starting to panic or should I be concerned? My vet is out of town until monday. I have doxycycline here but it is 100 mg.
    One more question…until her wheezing stops altogether or at least for the most part…should I try to keep her in a crate or confined area like I did mostly during her actual treatment period. I am sure those worms are still trying to get out of there. Or is it fluid and inflamation making her wheeze?
    I will ask my vet for a lung xray next week…is that what I should ask for first?
    Thank you so much for your time.
    Paula B

  16. JAYNE GLENN says:

    Our 5 year old australian shepherd is showing no signs of illness after his his heartworm treament – 2 injections , 24 hours apart. He is home. Nothing more that a little bit of coughing at times. He is doing remarkably well! I thought he was going to be really sick after the injections, such as coughing a lot. Not so! Just after 2 weeks of his treatment he already has more energy. Thanks to an excellent Dr. who put him on all the needed drugs for heart worm treatment:
    NOW A HAPPY OWNER OF A HEALTHIER SHEPHERD! He is already showing better quality of life, and it has only been 2 weeks after his injections. Best wishes to you and your companion. They can be saved! Ours was. -jayne

  17. paula b says:

    Hi Doc! I had shyanne’s lungs and heart xrayed vet says it looks what she would expect after having heartworm…still thinks she should stay on 10 mg. pred bid for another month because she is still breathing hard..sort of wheezing a bit when she gets excited or runs. She thinks Shyanne should heal some though…anything to add to this? Paula B

  18. Doc says:

    I think that the doctor “on the ground” is in the best position to judge the situation. Your veterinarian has probably already told you that you will have to taper off slowly after taking that much pred for that long a time. Good luck!

  19. paula b says:

    Dear Dr.
    I have a question about a foster dog I have had since a puppy…she is now about 10 months old. She was brought to the vet by the dog warden because she was tilting her head to the side..he thought she might have been injured. The vet said she had vestibular disease and treated her with antibiotics I think…I ended up fostering her. She has been very playful, energetic, and a happy girl always since then…but usually she still tilts her head slightly to the right side. I noticed the past week she seemed somewhat not herself…not as playful with the other dogs..and was tilting her head to the right again even more so….so I took her back to the vet…she looked inside her ear with the lighted instrument…said she had an infection in her inner ear (or was it middle ear, same thing?) and it had lots of puss in it. She told me to give her 250 mg. Cipro bid…and to recheck in 2 weeks…right now after all of this time fostering her..I have someone actually interested in adopting her….my vet said I should hold off adopting her at least till she gets rechecked. She almost sounds like she thinks something more serious is going on. I have tried reading up on Vestibular Disease on the internet…I just am getting more confused. Should she get an MRI to see if there is a tumor? or is she possibly for some reason more prone to inner ear infections which causes Vestibular Disease or is it the other way around? the disease causes the infections? She is back to her old self already after one dose of meds…playing, running, rough housing with the other dogs. She eats like a little pig and never acts dizzy or sick. Even now with the infection. Any advice you could give me I would greatly appreaciate…especially since she has a good chance of a “forever” home…I want to be able to be honest about her condition.
    Thanks so much,
    Paula b.

  20. Doc says:

    Hello, Paula,

    I realize that in a fostering situation it is difficult to spend large amounts of money. However, if there was lots of pus and no eardrum (which I would infer from the statement that there was a “middle ear infection with pus”), the middle ear (tympanic bulla) will need to have any debris removed from it. Otherwise, when you stop the antibiotics, you still have gunk sitting there to start the problem over again. Ideally, the area would have been cultured instead of just starting on the Cipro, but this may not have been an option under you circumstances. You might ask your veterinarian about this, and see if he/she has the instrumentation to visualize and irrigate the area. If not, perhaps he/she could refer you to someone who does.

    The doctor who is seeing the case is in a better position to evaluate it than I am, but it sounds as though this dog will have recurring problems if the middle ear is not addressed.

    Thanks for reading and writing,

  21. paula b says:

    Hello, this is Paula again about another foster dog that I adopted out back in December.
    She is a GSD mix and about 8 months old now. She was the runt of the litter.
    I was just told she has Chronic Kidney Failure and Severe Hip Dysplasia. Their vet gave her 2 mo to 2 years to live. She wondered if any of the other puppies in the litter had this (I have not heard so far)and if there would be anything else to do besides diet change. She had bloodwork and xrays done. She is devastated of course. One of the siblings did pass away months ago from congestive heart failure. could all of these puppies from this litter be doomed? I hope not!

  22. Doc says:

    Hello, Paula,

    It is certainly possible that the other puppies in the litter will have their own genetic anomalies. It certainly doesn’t sound like the parents contributed a very good mix for either of these puppies.

    I wish that I could give you some useful information, but really, your guess is as good as mine at this point.

    Thanks for reading and writing.

  23. Rome says:


    I recently treated my 5 yr old labrador for HW. He is doing good and responding well to the medications. I took him in on 6/26 and picked him up the 6/27 evening. Is a little coughing normal? Also hes been panting a lot but its kind of hard to tell whether its bothering him because he always panted before. I know that he’s supposed to be crated but is okay for him to be confined in a small area such as the bathroom? he doesnt wanna be in a crate. also is it normal for him to lose a little weight? we noticed substantial weight loss and its only been a few days. thank you so much for reading this…


  24. Doc says:

    Hello, Rome,

    A little coughing is common, but if your dog is feeling bad, eating poorly, etc., you should definitely let your veterinarian know. The weight loss is troubling. Four or five days post-treatment is when the worms are usually dying and shifting position, causing the dog to feel bad.

    A crate is only necessary if the dog is having a lot of respiratory distress, coughing up blood, etc. You don’t want the dog engaging in either prolonged aerobic exercise or heavy bursts of activity. The bathroom is not too big.

    The key is to have the dog take it easy. You just have to use some judgment as to what will be most effective in that line. If the dog turns cartwheels in the crate, but is quiet in the living room, then go for the living room.

    Most dogs would be fine roaming the home, or being walked on a leash.

    Call your veterinarian and let them know how your dog is doing.

    Thanks for reading and writing.

  25. Rome says:

    Thanks for the quick reply. just wanted ask a few more questions. he hasn’t had any bowel movements for the past five days. is this normal? i’ve been feeding him bland diet (boiled chicken and rice) ever since he got home from the vet because he wouldn’t eat his regular diet. i find this weird because ever since started his medication, he’s been devouring his food. a lot is going i but is coming out. he’s urinating regularly. thank you!

  26. Doc says:

    Having no bowel movements for 5 days is not normal. It is also not a common feature of dogs undergoing heartworm treatment. You should consult your dog’s veterinarian. It is possible that he may want to put your dog on a mild laxative. It should be harmless to add 1 teaspoon of psyllium muciloid powder (generic, non-flavored, non-fizzy “Metamucil”) per 20 pounds of body weight, per feeding. Just mix the powder with his food.

    Don’t forget to notify your regular doctor of your concerns.

  27. Sam Vail says:

    My dog has heart worms, and he coughs once in a while, he’s active yet, but has always been skinny, but now his ribs are showing more than ever. My local vet wants about 800 bucks to treat him, but I just can’t afford Immiticide. Can I get it anywhere and inject it myself, follow the confinement directions, and then put him on a preventative? He’s a 3 year old 60 pound pit bull that my family and i adore.

  28. Doc says:

    Hello, Sam,

    Immiticide is a legend drug, not available for sale over the counter. Improper injection technique can result in really nasty sore places that slough out (like a brown recluse spider bite). It’s also not cheap, even the wholesale cost.

    Most folks only hospitalize the dog for the injection, not for the several weeks of convalescence.

    You might ask you veterinarian what their fee includes. Our fee includes as many follow-up visits as are needed if the dog has complications (no charge, even if at night), medicine to clear the bloodstream of baby heartworms (later in the process), and blood tests to be sure that the worms are gone. In anticipation of handling these things, we do build some extra into the fee. It’s not just the medication.

    If you’re not happy with your veterinarian’s answers, you might seek a second opinion.

    There really is not a “roll your own” treatment that will help your dog.

    Thanks for reading and writing.

  29. Nancy says:

    Hello. Three weeks ago I adopted a wonderful dog who came into the shelter as a neglect case. His ears had been chewed I think by mites and he had the early stages of heartworm disease. A week ago he received two immiticide injections which he seems to have tolerated fairly well. He has had also diarrhea intermittently since I brought him back from the pound. I thought the loose stools could be related to the change in his diet when I brought him home, but yesterday he had a pretty bad case of diarrhea and he also vomited a lot. No blood or dark discoloration, just a lot of vomit and diarrhea. My vet thought the problem probably wasn’t related to the heartworm treatment and recommended that I give him to a bland (chicken and rice) diet for a few meals. Here’s my question – given that my dog was neglected, I am wondering if he might have intestinal parasites and if so, if those would have been killed by the heartworm treatment. I did see something in his vomit that looked like a garden slug (quarter inch thick and two to three inches long)- could that be an intestinal parasite coming up? Thanks very much.

  30. Doc says:

    Hello, Nancy,

    The thing that looked like a slug may actually BE a slug. It does not sound like any of the common dog intestinal parasites. Dogs will, unfortunately, eat virtually anything that can’t outrun them, and a slug cannot outrun them.

    The heartworm treatment (Immiticide injections) would be unlikely to cause either the vomiting or diarrhea. The treatment also would NOT have done anything to help rid the dog of intestinal parasites.

    You should definitely take a new stool specimen to your veterinarian to recheck that situation – about a tablespoonful of stool that is less than 12 hours hold is ideal.

    It is okay to give DOGS (not cats) Pepto Bismol as a symptomatic treatment, and your veterinarian can actually detect more in a firm stool than a loose one. Give about 1/4cc Pepto Bismol per pound of body weight, repeat as needed, as you would for a person.

    Thanks for reading and writing.

  31. kim says:

    I have been told, and it has been recommended to me by veterinarians and dog rescues and vet techs I have spoken to online (my own vet refuses to do it, though) that I should use heartgard to treat my 2 dog’s heartworms
    I live in South Louisiana, and they both tested positive after being on monthly preventative (before I got them..((they were rescues)) so I’m not sure which one was being used)
    the theory behind it, as far as I can gather is that the heartgard keeps new heartworms from moving in, while allowing the old ones to eventually die.. slowly, instead of all at once.. which, in effect would eventually leave the dog hw free
    is this true? is it really that simple?
    I’ve been told that there is very little risk to this form of “treatment” even though it could take a couple of years to completely get rid of the little buggers, because all the worms don’t die at once, thus not creating as bad a problem with the potential for the dead worms causing a clot

  32. Doc says:

    Hello, Kim,

    Here are the pros and cons of your situation, as I understand them after talking extensively with the “big boys”.

    It is almost certainly safe for you to give the Heartgard to these dogs, even though they already have heartworms. And yes, even though I am having problems with less than 100% effectiveness, this should still keep the dogs from acquiring any major amount of new heartworms.

    As far as the adult worms present, the Heartgard has a pretty minimal effect. Their normal lifespan (no interference from drugs) is about four years. It will take at least two years for the Heartgard to kill them, maybe longer. So, it shortens their lifespan, but it sure isn’t dramatic.

    In the meantime, if you have a small number of adult worms present, they are unlikely to cause much heart damage. If the dog is athletic and vigorous, these worms (even in small numbers) get whipped around on the inside of the pulmonary arteries. This is not so great, and does damage them. If the dog is a couch potato, this effect is minimal.

    When you treat the dog with Immiticide, you know that the worms will be dying in the next few days. You know that you need to restrict the dog’s activity for the next few weeks. You know that you need to be watchful for the bad effects of the worms dying, shifting position and breaking up and clogging up arteries (coughing, difficulty breathing, fever, loss of appetite, coughing up even a drop of blood, or just generally not feeling good).

    When the worms die “sometime in the next two or three years”, you will NOT know when it is coming. You will NOT be restricting the dog’s activity during that crucial time. You will NOT be alert and watchful for signs of the worms’ demise.

    If the dogs are ancient couch potatoes who do little and don’t have much time left to do it in, yeah, I’d go with the Heartgard. If there just is no money to treat the dogs with Immiticide, by all means DO put them on the Heartgard.

    If the dogs are young and active, get them cleared out with the Immiticide.

    That’s my take on it, speaking in broad, general terms. As far as advising you on a particular dog, you really need to talk to a veterinarian who can evaluate the dog in person. Internet advice is often worth what it costs.

    Thanks for reading and writing.

  33. Michelle S says:

    I have a 5 yo Blue Heeler who has had his first injection of immeticide three weeks ago. He has had no problems so far. I am keeping him in a horse stall with a fan as he is a nervous wreck in the house. And with the stall, I do not need to walk him (he wants to trot even on the shortest leash), I simply clean his stall 2X daily while he eats just like the horses. The second doses will be given next week and he will be required to stay overnight. I was wondering if there is a time when he is in the most danger of having complications. If so I would like to put a crate in the stall to confine him even more. I did not think of this for the first injection. Also will he be in greater danger with the second dose or the first. Just would like to know what to expect and when I should try to be home to watch him the most. Thanks in advance.

  34. Doc says:

    Hello, Michelle,

    Statistically, the single dose of Immiticide kills about one-third of the worms present: the weakest ones. The two-dose, two-day treatment kills 91% of the worms whether you give a preliminary dose or not. The combination of the full three doses kills 98% of worms (all of them, we hope, most of the time).

    The biggest chance of a reaction is when the worms die and shift position, three to five days after treatment. This can be worse with the single injection, or it can be worse after the two-injection phase of treatment. This is not predictable. It just depends on how many worms there are and when they die.

    I would not crate him unless he is showing signs of distress: lots of coughing, difficult breathing, coughing up blood, high temperature, not eating. Confinement in the stall should be adequate otherwise. You are trying to avoid aerobic exercise, the kind that elevates heart rate and blood pressure.

    Thanks for reading and writing.

  35. Jennie says:

    Hi Doc,

    We rescued our manchester terrier mix, Hannah, a couple of months ago. She tested positive for heartworms. The vet put her on antibiotics to kill the organism that I guess lives symbiotically with the female worms. That was a 30-day course. Then she went in on Oct. 20th for her first injection. She was super healthy to begin with because I beefed her up with a healthy diet and colostrum supplements the month before the actual injection. So far she has not shown any adverse effects from the initial immiticide injection. No pain, and only one short coughing fit, but I think that was because she drank water too fast. We have not been walking her at all and I have been doing my best to keep her still. She is not a particularly hyper dog, but every once in a while she does get excited. Of course that nearly gives me a heart attack. She is mostly very calm, likes to ride in the car, and REALLY misses her walks. The vet has her on a staggered dosage of prednisone which she will finish up next week. It seems to stress her out more when she is crated, so we leave her out in the house if we have to be gone. She has a doggy door and our backyard has a built in dog run, so I can close off the rest of the yard to her and she can only roam a short distance from her dog door. She has to go in on Nov. 20th for a second round of shots followed by another month of quiet. I guess my question is this: Can she go on very short walks on leash? She acts like she feels fine, but I don’t want to do ANYTHING to jeopardize her successful recovery.

  36. Doc says:

    Hello, Jennie,

    You should feel free to share your concerns with the doctor who is treating your dog, as he/she is best equipped to address your specific case. The course of treatment you have described is very thorough and indicates to me that your doctor is doing a great job.

    Generally speaking, walks on the leash are okay. What we are trying to avoid is hard-charging, aerobic exercise. We don’t want increased blood pressure that pushes the chunks of dead worm tighter into the smaller arteries. We also don’t want increased blood pressure blowing out a damaged artery.

    SO, if we walk calmly at heel, that’s great. If the dog is acting like a nut, cartwheeling through her collar, and doing the power-pull against the leash, then that’s not so great. Just walking isn’t going to raise the heart-rate and blood-pressure. Acting like a nut (even if it’s not just an act) is going to increase the risk of problems.

    You just have to evaluate the dog’s behavior in the circumstances to make the best decision (as when you elected to un-crate her in the home).

    Thanks for reading and writing.

  37. Jennie says:

    Thank you! I believe we do have a good vet, but getting this kind of real information has been like pulling teeth.

    She does walk calmly and was so wiggly happy when she saw us putting on our “walking shoes” again!

    Thanks for the good specifics. I feel less out to sea about this now.

  38. Lynn says:

    My heart goes out to everyone who’s pet has heartworm disease. On June 11, 2008 my husband and I rescued a 3 yr old Eskie. He was surrendered to a NY shelter than placed with an Eskie rescue organization. He was posted on Petfinders as healthy and UTD (up to date) on vaccines, altered and microchipped. I believe the chip shoud be decided by the adopter but, that is another story. Upon the first visit to my vet with “Snowy” he tested positive for HW. Immediately we started the proper treatment plan. Snowy did not feel very well from the injections and threw up his water for the first few days. He felt better as the weeks went on only to go through the misery of the next injection. He had a total of three injections along with medications. He had a severe case of HW. When the treatments were done I continued to bring him to the vet for evaluations. For the next three months he was feeling good and behaving like a healthy dog should. I couldn’t wait to have the “sixth month HW test” that is administered after treatment for an accurate result… to hear he is HW negative. On December 2nd Snowy started coughing and seemed to have labored breathing so I brought him to the vet. They checked his gums which were a pale, grayish pink… a bad sign of lack of oxygen. They took an x-ray and blood and put him on oxygen. The blood (still) showed HW positve. The x-ray showed an enlarged heart but his lungs were good. Because he needed round the clock oxygen we had to bring him to an emergency vet a half hour away. We got there and Snowy was put on oxygen. Without going into the details of the devestation we were going through… because this was just 13 days ago, we got home after leaving him at the emergency vet only to receive a phone call that he had passed away just 10 minutes after we left. To say we are heartbroken is the biggest understatement of my lifetime. I am not posting to ask a question but to inform everyone who reads this…. PLEASE do NOT take for granted that a pet posted as healthy and UTD on shots means they are also HW negative. Unfortunately, shelters and rescue organizations are not working together on this issue. It is crucial when enquiring about a pet that a HW test be administered. If you aren’t able to handle the expense ($1,800.00 in our case) and the heartache of losing your precious pet, this will save you a lot of grief. I have been in the process of communicating all my concerns on this issue with both the NY shelter and the rescue organization from which Snowy came. This is a serious disease that effects every state in the country because mosquitos are everywhere. Granted, it’s worse in the southern states but not to be taken lightly in the northern states. HW prevention should be given year round with no breaks in between whatsover. I pray every precious pet on this website that is going through HW treatments comes through it successfully. We were blessed with our beloved Snowy for only six short months. I only rescue dogs but would be just as cautious with breeders and other sources of acquiring dogs.
    Heartbroken in NH

  39. Doc says:

    Hello, Lynn,

    I am sorry for your loss. This is always the kicker when someone adopts that dog who needs a home. Most other common problems are easily treatable with minimal expense.

    It just kills me when someone is trying to “do the right thing” and find that they have adopted this major medical problem.

    Fortunately, most folks have good results, but even so, it is still a big investment of time, money, and worry.

    Best wishes.

  40. Lynn says:

    Thank you for your response and sympathy. If just one person is helped through our unfortunate circumstance, and is spared the heartache, it is worth it for me to share how important it is to make sure of the status of the HW results before acquiring a pet.

  41. Suzanne says:

    Wow. I stumbled on Dr. Mobley’s blog/site while being one of those “bad” foster parents Googling for heartworm treatment information. Our beautiful, 7-yr.-old rescue GSD, call sign “Turk,” just had his first injection of Immiticide today after a month of Doxycycline, prednisone, & blood draws to ensure his platelets were w/in range first. Our heart also goes out to Lynne & her family re. Eskie. We were told by the Florida Keys SPCA that Turk was strong heartworm positive and they’d cover his treatment, and we may adopt him when he’s medically clear. He is a dream dog. Well trained, loving, responsive, and, needless to say, we adore him. He is a little restless today, trying to find a space/place to get comfortable, but seems A-o.k. so far. We’ll watch him closely in the upcoming week and beyond. Back to my point, in all the posts/responses, what calm, collected, compassionate wisdom. I can tell animals in your care, Dr. Mobley, are lucky, indeed. Thank you for giving of your time to help. All the way from Paradise (a.k.a. Key West), Suzanne (& Turk)

  42. Sue says:

    As seems to be the common story here, we adopted a wonderful 2 year old Scotty mix 2 weeks ago. Discovered 4 days after bringing her home she had Class II heartworm disease, no anemia, liver enzymes slightly elevated, very mild enlargement of arteries. Otherwise healthy and a real sweetheart. She had her 2 injections last Tuesday & Wednesday and has been having a very rough time of it. Heartworm is not common in our area, so no one seems to have any real definitive answers for me. She had back pain for a couple days and I suspect by her walk it is still tender. She began coughing on Saturday and had some wheezing, then more coughing and retching with a fever on Sunday. After an emergency visit to an on call vet we got anti inflammatorys that helped with fever and she rallied some. Yesterday we again had a lot of coughing with some panting and gagging. This has been accepted by the area vets as just the way it goes. In the night she coughed up 3 small pools of saliva/mucus/blood. She has not been interested in her dry food but will eat canned food and is still drinking water. After calling the vet this morning, they suggested bringing her in and starting her on a course of steroids. My husband felt that she was better this afternoon – more alert, less labored breathing, less coughing, no more blood and cancelled the appointment. Here is my question (finally!)…how bad is bad with the post treatment reaction? There have been a couple times when she has acted so sick I have wondered if she would live. She is confined and only going out on a leash to go potty – otherwise crated or in a small room on her pillow. She is not a hyper dog and spends most her time just laying there since treatment. Is this just the way of it and hopefully it will be over soon? Should I override my husband and take her back to the vet for steroids? How long do these severe symptoms go on and are they “normal” given the treatment? No one seems to know much here, so I am hoping you can advise.

    • Anita says:

      My 8 yr. Old terror mix turned blind 1 week after heartworm and rabbies vaccine was given. He went in on Jan 21 2021 for routine checkup tests came back good they gave hime his annual rabbies vaccine and heartworm med. and sent him home he wasn’t himself hee just slept usually he wants to play ball 2 day later we noticed his belly was swollen and very hard took him back to vet they did an altrasound and found nothing a week later still swollen tummy, breathing difficulties,hard time walking and he was running into things like he was blind took him back for another visit and still nothing asked to check his eyes and he had no reaction to light and was pronounced blind, this I’m sure is from the rabbies or heartworm med or both together my heart is broken and I can only imagine how scared and confused my Joey is, its been 2 months and he’s not any better I wish I would have never made that appt. To the vet that day I’d still have my healthy little guy. To anyone who has suffered as well my heart goes out to you.

      • Doc says:

        Hello, Anita,
        I can understand your feelings. Correlation in time is not always cause and effect. Millions of dogs receive these medications together with no ill effects. You don’t need to feel guilty about this.

  43. Doc says:

    Hello, Sue,

    I don’t know what part of the country you are in, but it does sound like they don’t do a lot of heartworm treatments.

    Corticosteroids are THE treatment of choice for heartworm complications. We would have started them at the first sign of difficulty. Waiting until the dog is having so much trouble worsens the prognosis. You should get the dog and and get treatment started as soon as possible.

    There is always going to be some inflammation present in the pulmonary arteries as the worms shift position and break up. Even when the dog looks okay outwardly (and your dog DOES NOT), inflammation is taking place. For this reason, many doctors are now starting anti-inflammatory doses of prednisone routinely when the dog goes home, tapering the dose slowly over the next four weeks.

    Whenever the dog shows any significant signs of difficulty (and your dog certainly is) we want to start steroid treatment ASAP.

    Complications that are minor to start with can progressively become worse and the steroids can often prevent that.

    The back soreness you observed initially was most likely due to the injections themselves. Even when severe, this is usually very temporary, 2 or 3 days at most. The problems you are seeing now are most likely related to the inflammation in the pulmonary arteries due to the dead worms. This makes the arteries swell shut, restricting flow, increasing pressure, back-pressure against the right heart, oozing fluid into the lungs, and possibly rupturing an artery.

    In addition to the steroids, strictly restricted activity (cage rest) is important, and it’s great that you are doing that.

    I really cannot prescribe for your dog as I can neither see nor examine it. However, I strongly recommend that you get her back in to your veterinarian for treatment. Even if she seems a little better today, she will still benefit greatly from the medication.

    The length of complications varies, but it takes the body several weeks to dissolve away the dead worms, so you are far from out of the woods.

    Please take your dog back for evaluation and treatment.

    Good luck.

  44. Fawn Richter says:

    I have enjoyed reading your thoughful responses to so many questions. here is mine asked with much respect.
    What are your thoughts on the “slow kill” method? A rescue I foster for recommends Doxy for a month (although I found a study that suggests 2w is better) then Ivermectin every 2w for up to a year until a neg result is met. The reasons are primarily to make the tx less harsh and of course financial.
    My second question is what HW tx is recommended for a lethal white HW+ Aussie. I believe they are in the Collie family and cannot have Ivermectin, right?

  45. Doc says:

    Hello, Fawn,

    The doxycycline is intended to kill a microorganism called Wohlbachia that infests the heartworm itself. Many researchers believe that a great deal of the reaction we see to the breakup of the dead worms is related to the presence of this organism. This is not a universally adopted practice, but is inexpensive and does no harm (unless the delay allows more heart and artery disease to develop in dogs who have clinical signs of disease, versus just a “positive blood test”).

    Even when the Wohlbachia is gone, you still have chunks of dead worm to deal with, and they WILL cause inflammation in the pulmonary arteries. The inflammation causes swelling of the blood vessel, which restricts its inner opening. This makes circulation in the lung tissue poor, and increases the pressure on the compromised artery, and increases the back-pressure the heart must pump against.

    This brings us to your question about using long-term ivermectin to kill the worms, and whether this is somehow “less harsh”. Dead worms are dead worms, no matter what kills them. When they die and drift downstream, it doesn’t matter what drug killed them or how long it took. They will still lodge and plug things up and cause inflammation.

    With the dramatic increase in the number of dogs who get small numbers of heartworms despite taking monthly ivermectin (Heartgard 30, etc.) I have serious doubts that taking ivermectin every two weeks is going to kill the heartworms. Previous studies documenting this noted that it took as long as two years for the worms to die with this treatment (they would die of old age in about four years). These studies were made before we began to see the apparent failure of the drug to prevent heartworms 100% (in the past 3 years). Since they are getting new worms, it’s hard for me to have confidence in the drug getting rid of the old ones.

    Even if we accept that giving ivermectin twice monthly would eventually kill the heartworms (and I am not confident of this), we have to ask if this is really a good thing. When we give the standard treatment of the Immiticide injections, we know that the worms will die within the next few days. Thus we are alert for signs of complications. We also are now giving the dogs prednisone after their treatment in order to minimize the inflammation experienced when the dead worms move.

    The bottom line is that we know when the worms will be dying and moving, so we can be on the alert and detect complications rapidly, and deal with them. We know that the dog’s activity should be restricted while the dead worms are clogging up the works, and we can do this for the next five or six weeks.

    If the worms were going to die at some unspecified time in the indefinite future, how in the dickens are you going to be on constant “red alert” for the next two years? Are you going to crate the dog for two years? Give him prednisone for two years? I submit that you will not be doing any of these things. Therefore, when the worms DO die, you are more likely to experience complications.

    Since complications are related to how many dead worms are breaking up and hitting the smaller pulmonary arteries, it would make sense that the dog would do better if the worms died one at a time over a long period of time. There is NO evidence to say that this is what happens with the ivermectin (if indeed, anything is happening with the ivermectin). Even if you could prove that “in six months, the worms began to die one at a time, regular as clockwork, one-tenth of the worms per month for ten months” (and this is absurd), would you crate the dog for ten months, starting six months from now?

    The sad fact of the business is that the Immiticide treatment is the only thing that we know is effective. We can reduce the risk by giving a half-treatment, and then waiting a month to give the full treatment. This also makes it more likely that ALL of the worms will be killed. (Unfortunately, there is no such thing as 100%, “always” or “never” when we’re talking about this).

    This (Immiticide treatment) would be the appropriate treatment for the Aussie. While they cannot tolerate high doses of ivermectin, they tolerate the preventive dose in Heartgard 30. You could certainly use Interceptor as your preventive instead, but it’s not going to be effective in ridding the dog of adult heartworms.

    It is certainly cheaper to give Ivermectin twice monthly for years than to do the Immiticide treatment. On the other hand, giving nothing is even cheaper. Doesn’t work, but it’s cheap.

    Sorry that I don’t have a quick fix for you.

    Thanks for reading and writing.

  46. E.C. says:

    My 3 yr. old rottie is vommitting. Mostly whole food. He is on Doxy and heartgard as its all we could afford. That alone hurt us some as we werent expecting it.

    He always choked up clear water I dint think much off it he drools more than that. And I know its common for dogs to drink or eat too fast and do that. Every know and then a lose food would come out but no big deal. Latly its getting worse and real food not just water from drinking to fast or food caught in the throat.

    Theres been no bile or green just his partial digested food. I know both drugs have vomiting side effects. Do you think its a side effect or just eating too fast or gutter gut. Tonight he puked 3-4 times and it really worried me.

    Before it was once if it was mostly just a hack thing and maybe water somteimes a little food mixed in. It usualy happens after feeding a couple of hours in. Never in the middle of day or night.

    But tonight after feeding it was bad. I thought he just got in to somthing on his walk as he does. He did get somthing in his eyes.

    He knew he was going to get sick too which was strange usualy it kind of surprises him or he runs off the carpet this time he wanted OUT and Pets! He was trying to warn us we just didnt pick up on it.

    I Started looking and found the side effects. If it is the doxycycline any suggestion on another. On the 15th of may we give him second dose of heartgard if that helps. He didnt seem to mind that. I dont know. We are just so short on money any advice would be helpful.

    Lucky we dont worry about activity, this is the laziest dog I’ve known. Happy all the time greets everyone, plays, but lazy. 160 pound lap dog.

    Smart too, shook his head no when I ask if he was OK. Nodes yes when I ask him if he needs go out. I didnt know you could train a dog do that. Too bad it was too late at the time. Always listen to your dog.

  47. Doc says:

    Hello, E.C.,

    I’m answering your question as best I can with the limited information that I have. Your veterinarian (who has actually seen your dog) is the best person to advise you. I am assuming that the vomiting didn’t start until after you started the doxycycline.

    Doxycycline causes nausea in a lot of individuals if you take it on an empty stomach. Sometimes it makes me, personally, nauseated even when I do take it after a meal (I have taken it after tick exposure and getting sick). You want a good drink of water afterwards, too, to be sure a capsule isn’t sticking in his esophagus halfway down. That can cause really severe inflammation.

    If you are waiting until after a meal to give the doxy, and he has trouble anyway, we might look at an acid-reducer. Some dogs will benefit from famotidine. This is the active ingredient in Pepsid-AC. Over-the-counter Pepsid-AC is a 10mg tablet. A 160 pound dog would need to take four of these once or twice daily.

    The purpose of the doxycycline is to kill Wohlbachia, a micro-organism that is necessary for the heartworm to thrive. If the Wohlbachia are killed, the microfilariae (the baby heartworms) die, and the adult heartworms shrink in size. When you stop the doxy, they will recover. The idea is to shrink things down and then do the Immiticide treatment. You should then have less reaction to the break-up of the dead worms.

    If your dog has clinical signs of heartworm disease (lung problems, coughing, poor exercise tolerance, etc.), you may see a little improvement with the doxycycline. It is considered safe to give the Heartgard-30 (Ivermectin) to keep from getting any more worms than you already have.

    Some dogs with heartworms don’t have a lot of heart damage yet, but they have a lot of problems with inflamed arteries in their lungs. These dogs often show dramatic (if temporary) improvement when treated with prednisone (a form of cortisone).

    Again, I urge you to contact your veterinarian with your concerns. Many times we send home medication, believing that we have explained things well, when people actually have a lot of un-answered questions. If we don’t get a call back, we assume things are going well. Give your doctor a chance to help you.

    Good luck.

  48. Kasey says:

    Hi there. I wanted everyone out there to hear my short story about Lucky- my 2 year old pit rescue. He is a very healthy boy who has outrun the healthiest shepards and other dogs at the dog park. his energy is amazing. April 20 he was diagnosed with heartworms a mid level amount. I have had him and my other dog on Sentinel since I got him a year ago. He was in foster care for 3 months prior to that with a negative HW test. Prior to that he was at a pound for 3 months. So my vet believes he got it before I had him- but here I am 766.$ later. I love- no, obsess over my dogs so I naturally worried when I was told no outings, walks or playing with his sister.2 months confinement. So my vet does the injection in a dosing like this: first shot- 2 wks later a checkup, then 2 weeks after that a 2nd injection with a 3rd 24 hours after. He gave Deramaxx to me to give an hour before each injection for pain.Lucky did well with the injection as it was 3 ccs each time but not with a gimormous long needle as most use- maybe 2 inches long..I had so many questions and couldnt find enough consistent information on the web- so thought my post will help others. He panted and trembled and drooled for a few hours after each injection. The hardest part is keeping him from playing. He has actually gained a pound in one month (as we just had the last injection yesterday). I encourage buying dog treats and chew bones!!! These keep him occupied in the crate. There are also interactive toys for dogs (just google those words). I love them. If your dog is not a chewer- keep ice chips or cubes in a bowl in the crate.It also helps him to keep hydrated.I am a police officer and work alot so when I am home Lucky is not in the crate but we lay around together (Ive gained 4 pounds in the last MONTH )and when I do need to be mobile- I put his leash on and tie it to my waist so I can keep him from springing off to run around the house.Oh and a Kong full of pnut butter will keep him quiet too!If anyone out there has questions feel free to email me and I can try to help. Good Luck!

  49. Doc says:

    Hello, Kasey,

    A 20-gauge, 1.5 inch needle is standard for the injection in larger dogs. You want it deep in the loin muscle (epaxial muscle). This muscle has no internal partitions of connective tissue, and the experts say that injecting here is “almost the same” as giving it intravenously. However, many dogs do experience soreness at the injection site.

    If one is giving cortisone for the inflammation that occurs with the death and break-up of the worms, you don’t want to give that along with NSAIDs, such as Deramaxx or Rimadyl. If no cortisone, then the NSAIDs should be fine.

    Since we are giving cortisone for the inflammation (dexamethasone injections, followed by prednisone tablets at home), if a dog still has problems, we will give Tylenol for additional relief, sometimes even Tylenol+Codeine.

    Even dogs that are REALLY sore tend to be fine in two or three days.

    The panting and drooling are related to the pain and some temporary nausea. These are by no means an universal experience. We keep many dogs overnight and the majority do not display these signs.

    In re “no playing”, what you want to avoid is increased heart rate and blood pressure. This means different things with different dogs. If a dog is pretty laid-back, there’s no reason not to let him go all over the house, and out for walks on a leash. If he’s a hard charger, things are more difficult. We obviously don’t want a prolonged run, but even short bursts of heavy activity can be a problem with a weakened pulmonary artery.

    Thanks for reading and writing.

  50. Sam says:

    I have a 4 yr old terrier mix who was rescued in Texas. He’s been with me in NY for 7 months. Only recently have I been able to take him to the vet since i’m unemployed, i just received my tax refund. He went in for tick removal and his first set of shots (rabies, distemper). To my dismay, they told me he tested positive for HW. He’s my sidekick, my buddy. He’s been behaving normally, healthy, loving, happy, protective… how a dog should behave. I have 2 cats that he tolerates and become his default playmates when he’s bored. He’s due to go in for his first HW treatment on Tuesday morning (6/2) and planned to stay overnight. Now, he’s become my very close companion… by that i mean he’s by my side all of the time. He sleeps with me, sits with me, goes on car rides with me. I fear that the overnight stay will stress him out. OR that when he arrives home, his protective nature will doom him to a clogged artery when he gets excited and barks at pedestrians from my bedroom window or when a tenant enters the building. When we go for walks, he jumps up and down from happiness to go outside. He can be a couch potato but he has his moments of outbursts. After reading the various posts i’m almost thinking that perhaps he’s happiest NOW than with treatment. I can’t afford this treatment but i will not hesitate to use every last penny to care for him and my cats. Part of my stress is also because i don’t currently have an income, i’m afraid of complications that i won’t be able to afford – NOW that really breaks my heart. I’ve contacted a society who will assist with vet bills, but it’s not guaranteed that they will help. I still haven’t heard back. I’m quite distraught.

  51. Doc says:

    Hello, Sam,

    I hear your concerns.

    While a night away from home is stressful, it is unlikely to have any significant effect on the heartworm treatment process. The worms do not die and shift position until several days after the treatment. This is when you need to be alert for coughing, fever, difficult breathing, loss of appetite, coughing up phlegm (possibly with flecks of blood), or just generally feeling bad.

    If you notice a sudden change in your dog’s behavior and the way he feels, you need to let your veterinarian know as soon as possible.

    As far as his sudden bursts of activity causing problems during the convalescent period, it is certainly true that we want to minimize this. However, it is neither possible nor desirable for the dog to lie still for 6 weeks. You just need to look at the way your buddy views life, and arrange things to keep the craziness at a minimum.

    Short bursts of activity can cause a problem, but are not as dangerous as prolonged aerobic exercise. Therefore, no running loose, no playing frisbee, etc.

    There is always a chance that complications could develop, but this is true if you leave the worms untreated, as well. The odds are that you will be adding years to your buddy’s life.

    Good luck.

    • Awie says:

      Hi doc!
      I appreciate all the work you have been doing here. I can’t seem to find out how to make a separate comment so I decided I will just reply here instead. My dog had his 7th heartworm treatment session earlier today, he then was walked by my cousin tonight who apparently let him speed up while walking aside from the separate instance of my dog accidentally running 2 feet because his leash was let go for a bit. He was panting after his walk. I can’t contact his vet right now because the clinic is closed by now. Should I be worried? Thank you so much!

  52. John says:


    My 8 year lab recently tested positive for heart worms. I have been faithful with the Heartguard and can’t imagine how this happened. My vet said that our region (Mississippi Delta region of Arkansas) has seen an increase in cases of heart worms even when preventative treatment is clearly been done.

    Is he blowing smoke or is there some evidence to suggest that heart worms may be developing some resistance?

    He said the test was at the lower end of the scale and that treatment should be successful, but I am seriously frustrated. If the once monthly doesn’t prevent them even when given timely and properly, what possible options are there. I don’t like putting her through heavy dose treatments, although I like heart worms even less.

    She is a working dog and will miss duck season due to this. It will be harder for her than me I think (she loves it).

    What is the deal with heartworms now?

    Thanks in advance for your input.

  53. Doc says:

    Hello, John,

    Starting in 2006, I began seeing a dramatic increase in the number of dogs who were supposedly taking preventive medicine year-round, yet were still coming up with a positive blood test. This has continued in 07,08 and 09.
    I don’t think you veterinarian is “blowing smoke”.

    My experience in treating these dogs to clear them of adult worms suggests that they have very few worms. In other words, the preventive prevented most of the heartworm development (from mosquito exposure), but not 100%.

    I covered this in as much detail as I know how in a six part series last spring. I also cover more on the heartworm treatment process. Here is the link to the first of those posts:

    In regards to missing duck season, there are two viewpoints here.

    Number ONE: If the dog has very few worms, then it probably won’t slow her down and she can hunt normally, being treated for the worms after the hunting season.

    Number TWO: If a dog is really athletic and active, then even a few worms cause more damage to the pulmonary arteries. The increased heart rate and blood pressure really whip the worms around and could cause significant damage.

    So THERE’S a difficult judgment call for you. If you want to play it as safe as possible, you treat her now. If you want to hunt, you treat her later.

    I’m not sure when duck season starts, but if you treat the dog now, most of them are ready to rock by six weeks after treatment. I would suggest that you speak with your veterinarian about the time table.

    As far as the medication that is used, that really almost never causes the dog a problem. It’s the breakup of the dead worms that you’re worried about.

    Read through that series of six articles and I hope that you will have a lot of your questions answered.

    Good luck.

  54. Ellen says:

    We got a rescued 8 yr.old Pomeranian. When we took her for her shots & checkup she tested positive for heartworms. Our Vet said her x-rays & labwork showed the damage was not too severe. Our Vet said he has had better results with 1 shot & then 2 in a month. She had her first shot & it has been 2 weeks. She is eating good, drinking water & lets us know when she has to go potty. But several times a day, at night & in the early morning, she lays on the sofa & just trembles & her breathing is a somewhat labored & I can tell she is feeling very bad. Then after a while she perks up & seems to feel pretty good until the next bad spell. Is this normal for her to have these bad spells around the same time every day? When should this begin to subside? Thanks for reading..we have just never gone thru this & have completely fallen in love with her. She had been named Miss Angel & she is that & more.

  55. Katelyn Johnson says:

    My rescue dog had his first injection Dec. 19. Prior to that he was on doxycycline for one month. Jan 26 and 27 he had two more injections. Now one week after the final injections he has a fever 103.9 and a slight cough. He coughed up a small amount of blood. We took him to the vet and he received and antiboitic injection and 10 days of doxycline. He has not been exercised and has stayed as quiet as he has allowed us to keep him (he’s a bit hyperactive). The vet said his heart and lungs sounded good. Are these normal side affects or could this be life threatening? Anything else we can do? Thank you for such an imformative article.

  56. Doc says:

    Hello, Katelyn,

    This isn’t “normal”, but it is certainly a common occurrence as the worms shift position and break up. This is usually the worst time in the treatment period, so if he gets through this, the prognosis is pretty good.

    If he is coughing a lot and coughing up blood, I would be thinking cage rest. I’d keep him as quiet as humanly possible for the next few days. Walk on leash only as long as needed to eliminate, and keep strictly confined the rest of the time.

    If I were treating the dog, he would also be on some form of cortisone to reduce the inflammation in the pulmonary arteries, opening their diameter and allowing for more flow of blood, therefore reducing the pressure and the risk of more bleeding. The Doxycycline does have some anti-inflammatory activity, independent of its effect on the Wohlbachia organism (the heartworm symbiote).

    The cage confinement would be the point I’d stress at the moment. Physical exertion could definitely increase the likelihood of a severe hemorrhage in the lungs.

    Good luck, and keep your veterinarian informed as to the dog’s progress.

  57. Lori Jobmann says:

    Our dog just head her second and third heartworm treatment. The vet injected her on Monday, then the third shot on Tuesday. We picked her up today. She has been fine, but when I took her out to eliminate, she had very watery light brown then bloody diarrhea. Is this to be expected?

  58. Lori Jobmann says:

    I forgot to mention, our dog, Talulah, is a two year old, 59 pound Louisiana Catahoula Leopard dog. She’s otherwise very healthy. And her first immiticide injection was a month ago, and she seemed to do just fine…ie. no diarrhea at all. Thank you so much for your help!

  59. Doc says:

    Hello Lori,

    The diarrhea is NOT an expected side effect. It is possible that your dog is just stressed out, and will clear up with symptomatic therapy, such as Pepto Bismol.

    However, you should really let your veterinarian know about this, as it is not something we expect or typically experience. He/she will want to know and to stay in touch with you.

    Good luck.

  60. Barb says:

    I just brought my sheltland sheepdog home from his heartworm treatment. Other than the most obvious (coughing,wheezing, fever, vomitting, and “feeling bad”) what signs of distress should I be watching for? Should we be checking color of gums (my brother suggested this but what am I looking for??) or anything of that nature? This is still only the second day of treatment, I just want to be prepared for anything. Thanks very much.

  61. Doc says:

    Hello, Barb,

    Most dogs have their greatest risk of complications when the worms die and shift position in the pulmonary arteries. This is usually 4 or 5 days after the treatment. It can happen sooner, it can happen weeks later. We keep the patient’s activity restricted so that any running and heavy exercise is avoided as much as possible.

    I ask my clients to look for coughing, difficult or heavy breathing, loss of appetite, fever (if he doesn’t seem to feel well, rectal temp is normally 101.5, so anything over 103), coughing up any blood (even if it’s mostly phlegm with just a drop of blood), and “just not feeling good”.

    Sometimes the dog is still eating, not coughing, etc., but you know your dog, and you can tell he does not feel well. You should contact your veterinarian when this occurs.

    If he seems mostly okay and coughs once at 4:00 AM, you can wait until 8:00 to call. Don’t wait two or three days, though, as the condition can worsen without treatment.

    Good luck.

  62. chris says:

    my dog just finished the last shot of the treatment last week she does not run jump or do any thing of that nature but she is coughing up blood what should i do

  63. Doc says:

    Hello, Chris,

    If she is coughing up blood, you should confine her to as small an area as possible, like a cage. We don’t want her moving around any more than is absolutely necessary. We want to keep her blood pressure from spiking and causing more bleeding, or blowing out where her body is trying to “patch” the leak. So, absolutely as little activity as possible.

    If you haven’t already done so, contact your veterinarian as soon as you can. He/she will want to get you on some anti-inflammatory doses of some type of cortisone as soon as possible.

    Good luck.

  64. Maggie says:

    Dear Doc,

    My dog had his first shot of injection on 5/18, going for the second and third shots in two weeks on 6/21 & 6/22. He was doing fine since the shot (he had diaherra for about 3 days right after the first shot though). We still take him out for walk twice a day for him to do his business (he doesn’t eliminate inside the apartment). He usually has light panting after a walk, but other than that he’s just doing fine (no coughing, good appetite). However, as the weather has gotten hotter the past couple of weeks, he has been panting much faster due to the heat (even just relaxing at home). I want to know how should I deal with the heat, the walk, and also the complications from the up coming second and third shot of the injection, as I understand the last two injection will be much harsher? Thank you for your help and passion to animals.

  65. Doc says:

    Hello, Maggie,

    Limit your dog’s exercise. Make the walks as short as possible. Avoid the worst heat of the day.

    The second go-round may kill more worms, or it may be about the same number. The first treatment of one injection of Immiticide usually kill the weaker worms, mostly males. If there are about the same number of females, the second round won’t be any worse (probably). If more, it may be worse.

    Be alert for coughing, shortness of breath, difficult breathing, coughing up even a drop of blood (even if coughing isn’t bad otherwise), poor appetite, fever, or just generally feeling bad (even if no other signs are noticed).

    If you see any of these things, let your veterinarian know as soon as possible.

    Good luck.

  66. says:

    Hey Doc,
    I have a quick question about pain management. We just rescued a catahoula mix dog (about 1 yr) from the pound last month. He started the heartworm treatments right after. Today, we picked him after shots 2 and 3 of his heart worm regimen. He did fine with the first shot- just a bit of coughing and stiffness in back legs. My concern is our vet doesn’t do the prednisone, cortisone or pain meds. Should I give him any OTC meds for pain? And if so, what kind? He seems a little stiff in his back area, but other than that- I can’t tell that he is in much pain. What do you think? Thanks, Sharon

  67. Doc says:

    Hello, Sharon,

    The soreness usually goes away in 2 or 3 days, even if severe.

    A forty-pound dog can take one regular strength tylenol up to 3 times daily for a couple of days. Most will tolerate this without a problem.

    No ibuprofen or naproxen (advil or aleve), as they can cause serious stomach problems, bleeding ulcers, etc.

    Good luck.

  68. sharon says:


    I just wanted to make sure my stinky little buddy wasn’t hurting too badly. I know the heart worm treatment is rough ..although I know the the worms dying and exiting is the worst part! Thank goodness we don’t get them! Thanks again. Sharon

  69. Jennifer says:

    Hi- very informative site. Thanks so much for the info!

    A little background: Last September we adopted what we and the vet have guessed is a jack russel/blue tick hound mix. She’s appx. 2-3 years of age at this time and 35 lbs. She tested HW- at this shelter, which does a PHENOMENAL job with their dogs and treats for HW before adoption. We had to have our first dose of HW preventative IN HAND before we could even sign the adoption papers and take her home. She did have a suture reaction from her spay operation that required warm compresses to deal with a nasy lump and blister that formed, but other than that she was great when we got her home.

    She’s very laid back, very obedient, easily trainable, smart and sweet as can be. Will occasionally have a good burst of energy running around the yard with kids or after a cat, but not a real hi octane dog. It has pretty much been this way since meeting her at the shelter, which was a big draw for us as we are not overly energetic people.

    I had noticed that she had what appeared to be allergy symptoms that did not go away during our first few months (bloodshot eyes, nasally sounding wheezing only when sleeping) so we changed her food to a fish based holistic formula and that seems to have improved. I did notice that she has stopped wanting to chase the ball as much as before, but I attributed that to the Memphis heat and also made a point to have her thyroid tested at her yearly visit. We had to stop our mile long walks because of the intolerable heat and humidity here during the summer months, so I am not sure how her actual activity tolerance is. She will also cough a really deep cough (only once or twice at a time, that sounds like she is coughing something up) a couple of times a week- but she eats anything she finds laying around, so I always assumed it was gagging because it was infrequent and not prolonged and she always looks at the ground whie doing so as if something is going to appear. In hindsight these might have been warning signs.

    I took her for her yearly checkup where our vet did her first bloodwork since adoption. She seemed great on external exam, but the vet did warn me there was potential for her to come back HW+ because she is a rescue and of that window where they are infected but not showing up in bloodwork. I assumed that was rare and we left his office in good shape. I was truthfully more concerned about the thyroid coming back wonky.

    Well, needless to say she came back HW+. I was in such shock that I did not get all the details on how advanced he suspects her case is or anything because this was Friday afternoon (it is Sunday night now). He was going to check with Novartis and see if they will help us with the treatment because she is a rescue and has been on their preventative meds for the last year. He said we would talk more early this coming week.

    He did say that he felt nearly 100% cofident she would be fine with treatment, and that it should only cost us $300 to treat her. (He is a small town vet as well and does not push for services that are not necessary.) He said he had never lost a dog in his practice to heartworms because if he does not feel they have a good prognosis he will not put the dog and owner through the expense and physical/emotional toll of treatment.

    From what I have read online this weekend, I am assuming he is planning to do the 2 dose method. He said she would need to stay one night at his practice, and that she would need to be kept calm for 30 days following treatment.

    I am not certain if he routinely prescribes the antibiotic prior to the immiticide, but I intend to request that ahead of time if he does not usually do so. I am mainly concerned about serious complications from worm die-off. We are home most of the time (I homeschool) so supervision and restricted activity shouldn’t be much of a problem provided she does not resist spending a lot more time in her crate. I was wondering how frequent the serious complications are and if we would be wise to get steroids in her system immediately after the immiticide treatment instead of waiting for a potential problem to develop. I have not known this vet for very long, so I don’t want to question his treatment plan, but do want to do what is best for our sweet girl. I know he is not out to make a huge profit from the treatment since this cost is remarkably lower than most I have seen.

    Also, we are right in the midst of the Mississippi river area where dogs who have proven record of being on heartworm preventative like clockwork are testing positive despite all responsible measures. ( This has happened to people we know, and several of their friends, as well as hearing the same from the shelter.)What should we do in the months to come to prevent re-infection if she does well through the coming treatment? Keeping her on her regular preventative is a given.

    Any suggestions to maximize the chance we have a happy outcome? We have a lot of emotional investment in her and it would be really hard to lose her. However, we are not able to invest thousands of dollars into treatment either, so we are eager to do our best to prevent serious problems wherever possible.

  70. Doc says:

    Hello, Jennifer,

    It sounds like you have adopted a great dog, and that you are developing a good relationship with your veterinarian.

    I agree with you that the extreme heat makes it difficult to evaluate the change in the dog’s exercise tolerance (I’m about 100 miles from Memphis, and it’s been 100 degrees and high humidity for the last six weeks.)

    Under the circumstances you describe, with a negative test last year, one would expect the dog to have only a small burden of adult heartworms. This is not guaranteed, and would depend on the level of mosquito exposure and the dog’s individual resistance to the parasites.

    If you want to “everything”, then you could certainly ask for the doxycycline. Doxycycline inhibits Wohlbachia, a microbe that is beneficial to the heartworm.

    Giving this medicine for 4 weeks prior to the Immiticide injections (to kill the heartworms) causes the worms to become weaker (thus more susceptible to being killed by the medicine) and acutally physically smaller (so less junk to clog up the blood vessels, and less for the white blood cells to have to clear out).

    Treating the adult heartworms in two stages is considered to be safer than killing them all at once. If you have only a few worms, this would not be a big benefit. On the other hand, if you have a lot of worms, then killing half now and half later would be easier on the dog when the dead worms go downstream and lodge.

    The two-stage treatment consists of giving only a single injection of Immiticide (which will kill the weaker worms), then four more weeks of doxycycline. When the body has gotten rid of the first batch, one gives the two injections, 24 hours apart, and this kills the rest of the worms.

    Two injections given 24 hours apart will kill all of the worms in most dogs, but not all. This is true of the 3-injection, 2-stage protocol also.

    Giving the corticosteroids (I use prednisone) immediately following the Immiticide is not a universal practice. However, since I heard Dr. Tom Nelson (past president of the American Heartworm Society) recommend it, I have thought that it makes sense. You know that inflammation will occur, so why wait until it gets bad enough to make the dog sick? (Which is what I did “forever” until three years ago.)

    Now we give a strong anti-inflammatory dose of prednisone daily for the first seven days, then half that once daily for 7 days, then cotniue that lower dose once every 48 hours for 14 days. This has resulted in fewer night calls, because fewer dogs develop complications (that we can see). In fact very few dogs at all have developed outward complications.

    Again, that is not “standard” across the profession, but I really think it is helping our patients.

    Unfortunately, despite our best efforts, there are no guarantees. No matter what we do, sometimes a dead worm will lodge in such a way that a large vessel ruptures and the bleeding in the lungs is fatal. This is very rare, but it does happen.

    Keeping the dogs vigorous physical activity at a minimum is an important part of the aftercare. Changes in your dog’s attitude can reflect a problem coming on, so let your veterinarian know sooner, rather than later. Get the dog checked BEFORE it becomes an emergency.

    Most complications are minor and treatable if they do occur.

    Leaving the dog untreated is no solution, as the worms can cause a similar problem even if you have not yet treated the dog with Immiticide to kill them.

    We treated a dog this week who was known to be heartworm positive. They had put postponed treating her. Sunday evening she had severe pulmonary hemorrhage, and coughed up a LOT of blood. She’s on doxycycline and prednisone and cage rest now. I hope we will be successful in getting her through the whole process.

    I hope that this information is helpful to you.

  71. Ginny says:

    My little MaltiPoo just died three weeks after heartworm treatment with immiticide (first shot). She had been a rescue, and had tested strongly HW positive. She had been on doxycycline for a month prior to treatment and she seemed to feel fine. She had problems with breathing about a week after treatment, and she was kept for an additional two nights, put on steroids and oxygen. She came home on oral prednisone and had completed most of it when I could tell she began feeling really bad. I started to take her in but the vet was closing early that day and would be gone the next, so she would have been alone. I decided to keep her until the day after. The night before I was going to take her in, she collapsed in the yard when she went out to urinate. I took her to an emergency clinic, but she had died when we arrived. She had not been confined to a crate, but she was not an active dog and since she felt bad she had just been lying around except when she needed to go out. A post-mortem was done, and it showed an embolism, one dead worm and three dying. I keep turning this over and over in my mind because I feel responsible since she wasn’t kept crated. How could this have happened? Why would she die when she was not active at all?

  72. Doc says:

    Hello, Ginny,

    I am sorry for your loss.

    Some dogs have a bad, allergic type reaction when the heartworms die. This is similar to when a person who is seriously allergic to bee-stings has a reaction. They just turn blue and fall over.

    Unless you are standing right there with your epi-pen (epinephrine, aka adrenaline) it’s too late to do anything by the time you travel anywhere.

    This is quite rare, but I suspect it is what happened. It has nothing to do with whether the dog is crated or not. It is not your fault, and is impossible to predict.

    Sometimes our best just isn’t good enough, and that hurts.

    Best wishes and thanks for reading and writing.

  73. Jennifer Blake says:

    Hi! This is Jennifer from a couple of posts up with the HW+ blue tick/jack russell mix. I am happy to report that today is day 32 since her treatment, and we have been cleared for activity by our vet (he said once Halloween was over she should be good to go.) She tolerated the confinement, treatment and recovery without a hitch and we couldn’t be more pleased. We did the 2 shots 24 hours apart- our vet said that with all things considered he felt that was the best route. He could have done the other method with 1 shot then 2 more a month later, but if she were his particular pet he would do the treatment he did for Bella. He did do (when I asked about it) the doxy for 4 weeks prior and the prednisone for 2 weeks after. She only had one coughing/gagging episode about 2-3 weeks post treatment, and no other signs of discomfort at all. She has been energetic when on leash, eating just fine, content in her crate and an all around excellent patient. After I re-doggie proof the house today we are giving her free range inside, then I am going to give her a couple of more weeks on the leash in the yard just to play it safe.

    She has had a couple of coughs/gags the last week- but I suspect they were related to grooming herself as she is a heavy shedder. She did not seem in distress or anything. I was curious though if your previous message with the maltipoo that died and still had large worms intact and dying 3 weeks post treatment was normal. It was my understanding they should all be dead and dissolved before the 4 week mark. Is 30 days the appropriate length of time to wait for exercise to resume?

    Also, I understand the immiticide kills the adult HW, the monthly preventative (we use Interceptor) kills the microfiliare, but what kills the maturing worms if they are present? Is there another treatment step I need to ask about? Our HW preventative does not contain ivermectin.

    Thanks so much for your site and your down to earth advice and information. It is refreshing to see that there are vets out there that want to keep their patients healthy without fleecing their owners.

  74. Doc says:

    Hello, Jennifer,

    Most worms should be dead and dissolved by four to five weeks, but this is variable with the number of worms and the action of the dog’s own defense system. Those microscopic white blood cells have to eat those foot-long worms. It can be a slow process.

    I usually release my patients for exercise at 5 to 6 weeks post treatment.

    Yes, Immiticide kills the adults, preventives kill the microfilariae. We do not have medication to kill the developing worms. Dogs who are treated in the fall might turn up positive the following spring, as microfilariae that were missed in the summer’s preventive reach maturity six months later.

    Sometimes we try to delay treatment until six months after mosquito exposure. Sometimes this is not in the dog’s best interest, and we might have to treat twice. The rules are not hard and fast.

    I’m sorry you feel that some veterinarians are “fleecing the owners”. It costs a lot to keep a veterinary hospital running and ready for you, even if the doctor didn’t get paid a dime. My own hospital overhead is $32K per month, excluding any compensation for me, and I’m in a small, low-income town, in a rural area.

    I’m glad that your dog is doing well so far. It sounds like things are going to work out great.

    Thanks for reading and writing.

  75. Joanne Kutzler says:

    I certainly hope other dogs and owners do not have to go thru what we have been thru. I have a wonderful 1 3/4 yr old Irish Setter/Coon Hound rescue from Kentucky. She tested negative for HW January 9, 2010 and was given the preventative Revolution. I adopted her in Feb in Minnesota and she was started on Heartgard by my vet March 1. She received her Heartgard tablets faithfully from me the 1st of every month for the last 9 months(last one given this Nov 1). She showed absolutely no signs of any fatigue, coughing, or breathing difficulties. On Nov 2 we made a run to an emergency vet at 2am when my dog seemed uncomfortable and lethargic. While at the hospital she thru up, broke out in hives (bumps all over her body), had whitish gums, and abnormal lack of blood clotting.
    After much testing it was finally determined that she was HW positive.
    She has managed the 2 Immiticide shots and is feeling much better now after two 1/2 weeks.
    I do not understand how and why she got so ill so quickly and how she ended up HW positive. It was relatively easy to keep her inactive for the first 2 weeks since she really didn’t feel very good but now she getting her energy back. Any suggestions for how to keep my “born to run” youngster “calm” for another 6+ weeks ????
    Thank you very much for your wonderful website. Your thoughtful responses and expertise are greatly appreciated.

  76. Doc says:

    Hello, Joanne,

    I can certainly appreciate your frustration. Things have in no way gone according to our expectations in such a case.

    It is possible that your dog just has zilch resistance to the parasite – there are certainly dogs that do. I once had occasion to do a post-mortem on a dog that had moved from a mountainous area to our mosquito-infested area. He died at 18 months with a chest FULL of heartworms. Dogs that have been bred in this area would rarely see such a situation before 3 years, even with super-heavy exposure.

    In re keeping your dog quiet, I do not like to keep patients sedated. However, I have done so a few times. You might consider getting one of the DAP (dog appeasing pheromone) diffusers to put in his area of confinement. This often makes dogs more contented.

    Taking her for short walks on leash may help if she doesn’t get too rambunctious. Another thing you might do to relieve boredom would be to get those Kong toys where you hide the treats inside. Making her really work for her food may help keep her mind occupied.

    I’d also consider a lower-calorie, lower protein diet. No point feeding rocket fuel if you can’t let the dog blast off.

    Share your concerns with your veterinarian. In extreme cases, we have given sedatives for a couple of weeks or longer, though I do not like to.

    Thanks for your kind words, and good luck.

  77. Pam says:

    We have a 3 year old beagle that we adopted March 2009. She just finished being treated for heartworm when we adopted her. Since then she has tested positive for heartworm and been treated twice more. She just had her HW test and tested positive again. Why does she keep testing positive after being treated 3 times? I forgot to mention that she has been given Heartgard every month.

  78. Doc says:

    Hello, Pam,

    Has she had a full 3-dose protocol with Immiticide 3 times?

    Is she testing positive for microfilariae (baby heartworms)?

    Is she testing positive for adult worms (antigen test)?


    If it is just the microfilariae, sometimes treating for one month with doxycycline will clear them.

    There are certainly dogs where we have difficulty clearing the worms, but your situation sounds extreme.

    With more information, I might be able to tell you more. DO continue the Heartgard. Did you start it when you first got her?

  79. Jessica Meister says:

    My boxer had his first of three injections for heartworm today. The vet and staff who we respect said he was doing fine and told us to look out for increased resp., coughing, and temp. When we got home I noticed his eyes where really red, which can happen with is allergies, but his gums are also very red. He is def. slower, like I’d expect after all the medication, but not completely lethargic. His skin temp feels normal, I’m not sure how to take a dog’s temp and he isn’t panting. We also didn’t get sent home with any of the other medications people are writing about,(prednisone) or anything else. We don’t have a 24 hr vet so I’m not sure what to do because I only get an answering machine after hours. Can this wait til the morning?

  80. Angela says:

    We just found out our dog is HW positive. High Risk.

    We are taking him for treatment – two injections in 24 hours apart and four months of after care. One vet is 1300 for this treatment and a Low cost spay neuter clinic does this treatment for 350. Is the there any difference in treatment? I am worried about the cost (unemployed right now).

  81. Doc says:

    Hello, Angela,

    I can understand your concerns. Without knowing what is covered by those fees, I really can’t tell if you what the difference is.

    There are the initial injections of Immiticide which kill the heartworms. When we treat the dog, our fee would also cover a month of prednisone to go home, recheck at 6 weeks (when the heartworms should be dead and mostly dissolved) and four months, and blood test to be sure they are all gone at four months.

    We would also recheck the dog at no additional charge if there are signs of complications. There might be additional cost for other medicines, or if problems turn out to be unrelated to the heartworm treatment.

    I do not know what each hospital is actually providing for you. The low-cost option might have additional costs later on. You would just have to ask what is covered.

    Good luck.

  82. Doc says:

    Hello, Jessica,

    The only way to take the temperature is with a thermometer, rectally. The average normal temperature for a dog is 101.5 degrees Fahrenheit. A degree above or below would not worry me.

    Many dogs have pain and inflammation associated with the Immiticide injection. This is not really an emergency, but you need to let your veterinarian know about it.

    Even when the soreness is severe, it generally does not last more than three days. Do not use over-the-counter pain relievers without consulting your dog’s veterinarian. Many pills that are pretty safe for people can cause bleeding ulcers in dogs.

    A cold compress on the injection site can help. The injections are given in the heavy muscle of the lower back, what some call the loin area.

    Do call your veterinarian about this.

  83. LaVera Potter says:

    Glad to find you. I have been reading for days about heartworms looked at more pictures than i wanted to see. I have a seven year old standard poodle who has tested postive. I was going to have the standard treatment done but the more I read I was afraid. At the moment I are using the homeopathic method. I don’t know if it works but we shall see. He is eating well,active, but seems so thin. I have even been cooking for him in addition to dog food to try and put some weight on. Thank you for being honest I feel better. I will have him retested at 9week mark of treatment. He is coming up on week three.

  84. Doc says:

    Hello, LaVera,

    I fear that you will be disappointed in homeopathic treatment for the heartworms. Even Dr. Huisheng Xie, world famous holistic veterinarian, does not recommend this. Here is a website that gives you an introduction to him.

    Anything that kills the worms is going to result in dead worms moving downstream and clogging up blood vessels. Doesn’t matter whether it’s herbs, Immiticide, or space alien death rays. The dead worms are the problem, not the medicine.

    While there were some doctors advocating that the dog simply be kept on preventive medicine and wait for the worms to die of old age (3 to 4 years), the American Heartworm Society no longer feels that this is in the dog’s best interest. An exception would be an elderly dog with minimal physical activity and very few worms. He might live just as long without treatment as with it.

    When you treat with Immiticide, you have a very close idea of when the worms will be dying, and you can be watching the dog closely during those days and weeks. With the “wait for natural causes” method, you would need to be restricting the dog’s activity and taking great care to watch for complications for YEARS.

    Our standard protocol now is to pre-treat with doxycycline for 4 weeks, which weakens the worms. It makes them easier to kill, and physically smaller, so less blockage problems. Then we give a single injection of Immiticide, which kills the weaker worms (statistically about half the dog’s worm burden). The dog continues with doxycycline through the next four weeks (to keep the remaining worms weak), along with some cortisone to keep down inflammation in the pulmonary arteries.

    After those first bunch of dead worms are dissolved (about four weeks), the dog is treated with Immiticide once daily for two days. This kills the rest of the worms. Again, we give some cortisone for the inflammation.

    In six weeks, the dog gets a follow-up exam, and the dog is usually returned to normal activity. In four months a blood-test is done to be sure that the worms are gone.

    Best wishes.

  85. Leigh-Anne says:

    Great site, with lots of good information. I am getting conflicting information on the amount of “down time” a dog needs after hw treatment. Our foster, now forever family member, was treated for hw in November and the vet won’t release her for even minimal training classes until June. Also she still coughs ever so often (like a hairball cough) is this hw related or just a random cough?

  86. Doc says:

    Hello, Leigh-Anne,

    Your veterinarian has more familiarity with your particular dog than I possibly could, so it’s difficult for me to make specific recommendations.

    With dogs who have had low worm burdens and done well with treatment, we usually begin allowing gradual return to activity six weeks after the final Immiticide treatment.

    That being said, there are dogs who seem fine, but who have had an artery weakened during this process. When they resume activity and blood pressure rises, the artery breaks, and bleeding into the lungs occurs. This is a quite rare occurrence, but it can surely happen.

    The cough may be random, or there may be residual inflammation in the lungs. If a chest X-ray looks good, it is possible that a short round of corticosteroids could resolve that.

    It would be best for you to discuss this at more length with your veterinarian, and share your concerns with him/her.

    Best wishes.

  87. Doc says:

    Hello, Brandon,

    You should call your veterinarian about this. Some dogs are nauseated when they take doxycycline, and it can help if you give it after a meal.

    If he is not taking oral medications, then I cannot think of any heartworm treatment related problem that would make him throw up. That means something unusual is going on.

    While most dogs have almost no reaction to the Immiticide injections (other than temporary soreness at the injection site), it is certainly possible that a dog could be really sensitive to it. I have never seen this, but some people cannot take even an aspirin. It is certainly possible that your dog might have had a problem with the Immiticide.

    It is also possible that it is totally unrelated, i.e. he ate garbage, etc.

    In either case, you need to let your veterinarian know what is going on. When he/she doesn’t hear from you, they just assume that everything is going well. Let them know what is happening.

    Good luck.

  88. Cathy Hinchliffe says:

    my dog, Zeus, was treated today for heartworms and is breathing very rapidly and hasn’t stopped doing this since he has been home, I called the vet and she said to bring him in first thing in the morning because she was going home for the evening but he may have “thrown a worm” into his lungs. What does this mean? Is he going to die overnight? I don’t know what to do.

  89. Doc says:

    Hello, Cathie,

    In re: “throwing a worm” (lousy description)
    The worms live in the larger diameter pulmonary arteries (that take blood from the right side of the heart to the lungs to get oxygen), pretty close to the heart. When they die, they flow downstream and plug (or partially plug) the smaller blood vessels. This can make the dog feel pretty bad.

    The worms do not die for several days after the injections, but sometimes they can move downstream anyway. This can cause problems, as the lung downstream gets poor circulation, the artery is inflamed, there is more back-pressure against the heart’s pumping action.

    Another thing that could be happening is just pain from the injection site. The drug is pretty irritating, but dogs really have a variable response to this. There are dogs who have absolutely no discomfort, and others who are crying and you cannot touch their lower back without them screaming. In between you have dogs that are pretty painful, but not crying.

    Fortunately, this almost always passes in a couple of days, even with the really bad ones. We routinely give prednisone (a type of cortisone) for the inflammation, and sometimes find it necessary to give a pain-killer like Tramadol short term.

    Do not give over-the-counter pain relievers to your dog without consulting your veterinarian. Dogs have a much lower tolerance for things like Aleve and Ibuprofen. Bleeding ulcers can occur with a single dose.

    Keep your veterinarian updated on the dog’s condition. You can safely apply a cold compress to the lower back area where the injections were given. Keep the dog as quiet as possible until your veterinarian can recheck him. Most dogs get through the treatment with minimal complications. However, I know nothing about your dog’s case and you need to consult with the veterinarian who does.

    Good luck.

  90. Doug says:

    Hello Doc,

    I stumbled across this site last week and practically read every word on this page, I wanted to feel prepared when my dog began her heartworm treatment. I must say that it really eased my mind and I was ready for the beginning of treatment.

    We started my 9-yr old chow on treatment a day and a half ago (Thursday, April 20th). The vet opted for the shot, wait a month, then the two shots separated by 24 hours approach, she said it was the safest. So far there wasn’t any problems at the injection site and she was happier than ever when we picked her up from the vet (I know she might get down a bit in a few days when the worms start to die so I’m waiting for that).

    Anyways, my question is this. She’s currently on the last bit of prednisone (9 half pills remaining, to be taken every other day), has 2 days left of cephalexin, and is taking something-flex for arthritis in her hind legs. She was given the pred. and ceph. after we took her to the vet for a skin and ear infection (finished ear drop treatment).

    Trying not to ramble on here, the prednisone is making her eat and drink like no tomorrow. And obviously with eating comes elimination of the waste, which she has to do a lot of. She really likes to take her sweet time during a bathroom walk (on the leash, no more than 20-30 feet), sitting in the hot Florida sun/humidity. She’ll pant for a tad and drink a lot of water after returning from outside. Other than that she is sedentary every second she’s inside, shell get up to walk from room to room on occasion, that’s it. It’s just the fact that she cries to go out at such a large number now, sometimes 5-7 times a day. Unlike normal when it would be 2-3 times at most.

    Is this going to be dangerous when the worms begin to die? I’m really worried. How much is too much? She doesn’t jog nor run, but I’m worried if the 3-4 times a day she’s exposed to the mid-day weather will really beat down on her. Am I worrying too much about this?

    And one last thing, she has extremely bad gas, it clears rooms. Is that related to any of the meds/treatment?

    Thank you for everything you’re doing, it’s greatly appreciated.

  91. Doc says:

    Hello, Doug,

    The prednisone causes the dog to produce larger volumes of more dilute urine. When you get off the pred, the urination situation should return to normal.

    As long as she is just walking and not distressed or struggling, the trips outside should be no problem. We only recommend cage confinement when a dog is having serious complications, like trouble breathing, or coughing up blood.

    I doubt that the flatulence is related to the meds. Here’s a link to a great article from

  92. Sarah says:

    Hello Doc-
    First of all, thank you so much for the wealth of information you provide here! We adopted Max, a min pin mix, about 5 weeks ago off of the street. The vet said he is between 2-3 years old and he tested “faint” positive for heartworms and will be going in for his 2 shot/days treatment on June 13. Max is so very, very scared of storms. We live in Texas and our stormy season should be over now, but my biggest fear is that is we have a storm shortly after his treatment that it could cause major trouble. Max paces when the storms start and this lasts for about 30 mins or more, and he also shakes nonstop for the duration of the storm as well as some time post-storm. The Animal Rescue group doing his treatment (their cost is less than 1/3 of what our vet charges) said that we won’t be able to give Max anything to help calm him down in the event of a storm post HW treatment because of the uncertainty of how a medication may react with the treatment. Should I be concerned about the stress it would cause him if we have a bad storm after he receives his treatment? If so, do you have any helpful tips of how to help Max without medication? Thank you again for providing this site with such great information.

  93. Doc says:

    Hello, Sarah,
    I do not think that the thunderstorm anxiety will raise the dog’s blood pressure enough to increase your risks in the convalescent period after the Immiticide injections (6 weeks).
    I have not seen your dog, but generally I would not think a mild sedative would have any more adverse effect in this situation than otherwise.
    There is a product called Composure, made by Vetri-Science, that you might try. It is not a drug but a combination of vitamins, amino acids, and mysterious substances (no kidding).
    It is classified as a nutritional supplement, and comes in bite-sized treats. We have had several patients who do really well with this product. It hasn’t helped my own dog’s thunderstorm anxiety at all, but it has really helped a lot of our patients. It’s not expensive, and would be worth a try.

    Good luck.

  94. Jan John says:

    Thanks for so much information in so little space. I feel better about my dog’s recovery now. She does cough (no blood) and is tired after a short walk, but I think now that that’s the recovery at work and not a return to trouble with HW. You write 4 weeks and6 weeks after the second round of shots. I’ve been told 4 weeks is sufficient. Should I be thinking 6?

  95. Doc says:

    Hello, Jan John,

    I used to cut it off at four weeks and occasionally had a dog who had a little trouble on returning to activity. It didn’t happen often, but enough to bother me.

    I stretched it to six weeks several years ago, and this rarely happens now.

    Good luck.

  96. lynn says:

    I have a newly adopted heartworm positive shelter dog, 4 years old, Corgie/Chow Mix. He was ELISA Snap tested at first check-up because I wanted to put him on preventative. He was/is showing no clinical signs. We live in southern AZ. He did have X-rays that showed mild thoracic changes. He was also given a Desert Disease Panel to make sure he didn’t have Valley Fever or Tick Fever, to better proceed with a plan of action. He did have slightly elevated globulin levels. We are doing three months of Interceptor preventative to kill microfilaria and give juvenile worms time to mature to adults before starting adulticide (3 injections) 1 1st month, followed by back to back days 2nd month. We are in month 2 of giving the preventative. He had a mild reaction (vomiting and increased respitory rate)after given Interceptor the first time. He was treated w/steroid injection and Benadryl. Second dose went fine, I gave him Benadryl 30-45 min. before the Interceptor, as recommended by vet. I ran across some info. that recommended a second test if the dog is not from a hypoendemic area. The X-rays showing a slightly enlarged heart could be congenital? Would you recommend a second test before proceeding w/ Adulticide? Also, could you explain a little about the effectiveness of the Snap Test in identifying positive cases, and explain “specificity” and “sensitivity”?

    Thanks so much for giving your time to this blog.

  97. Doc says:

    Hello, Lynn,

    There are some specialists who feel that heartworm positive dogs are more likely to experience ill effects with Interceptor than with Heartgard (a different drug).

    I personally have not seen reactions with it, but some people have, and this may be part of your problem.

    The Snap Test is pretty specific, in that it is unlikely to react to things other than the protein from the adult female heartworm reproductive tract.

    Sensitivity refers to how many worms you would have to have present in order for the test to pick it up. This type of test (Snap, Abaxis, Witness, other “chair-side” tests) can give false negatives if fewer than four adult female worms are present.

    A second Snap test may not tell you what you want to know. If positive and there WERE some type of cross-reaction (non-specific) , it might be the same thing. If negative, it might mean that you just have very few worms and were lucky to find them the first time.

    In a case where there is uncertainty in our own lab, we always send a new sample out to an outside reference lab, like Antech.

    If there are very few heartworms, most dogs have disease only in the pulmonary arteries, not in the heart. However, there is no good way to count the worms unless the dog dies and you cut him open.

    If there are very few or no worms present, then the enlarged heart is probably due to something else, and could be worked up separately. An echocardiogram (ultrasound exam) can give you better information about the heart function than just an X-ray and physical exam.

    Since I have not seen your dog or its circumstances, I can only give general information. You really need to discuss this with your veterinarian.

    Best wishes.

  98. Holly says:

    Hi. I am confused about treatment for a very small rescued Brussels Griffon who is heartworm positive. She is young but very lethargic. The x-rays show a somewhat enlarged heart and pulmonary edema so my vet wants to use Immiticide. We are doing a month of doxy along with lasix and enalapril in the meantime. The rescue vet (without doing bloodwork or x-rays) says she’s too small for the shots and should do doxy and Heartguard only because of her size (6.5 lbs.)

    Does a small size increase a dog’s risk? I’m obviously very concerned about making the wrong decision here. It didn’t take this little girl long to be a very important part of our family. Thanks for any information.

  99. Doc says:

    Hello, Holly,

    Very small dogs don’t have much room for the dead heartworms to occupy. Three worms takes up a lot more of their pulmonary artery space than three worms in a German Shepherd Dog. They are indeed more likely to suffer complications from the breakup of the dead worms.

    HOWEVER, they are also more likely to suffer illness with a small number of worms, for the same reason. Thus, I feel they should be treated.

    The problem with just leaving the dog on Heartgard is that eventually, the heartworms present will die of old age. When this happens, the complications will be similar to those that would occur if you killed them with the treatment.

    The difference is, with the treatment, you are doing everything possible to minimize the complications, and you also know when they will occur. Thus you can be watching the dog more closely and restricting its activity during this time.

    You can’t do that for the rest of the dog’s life.

    It sounds to me like your veterinarian is proceeding appropriately. I cannot give specific advice, as I have not seen your dog.

    Discuss your concerns with your veterinarian.

    Good luck.

  100. Beth says:

    Thank you so much for putting this info up.

    Today I just found out that my dog Jewel (a German Shepard/Pit Bull mix) has heart worms. This has come as a hard blow for me.

    To make a long story short: she is 3 years old, we got her as a puppy and have always had her on prevention until last year sometime (got busy). It tears my heart to know that it is my fault.

    I don’t want her to go through the pain, and knowing that other problems could come up makes me feel even worse. Also, she isn’t too active, but every time she sees me she gets very exited (jumping around and everything). She is an all-the-time-outside-dog, so I can’t watch her 24/7. But the main thing is, we can’t pay for the treatment, and/or the other things that would happen. I am so sick over this and have cried for hours.
    Would be be worth it to get a second opinion? (we have been going to this vet hospital for years, though it was a different vet) or should we really consider putting her down? I know that that isn’t the best option, but at the moment I can’t see any other way to keep her from being in pain.

  101. Doc says:

    Hello, Beth,

    Not having seen your dog, it’s hard for me to give you specific advice.

    We have several patients whose owners are not able to do the treatment right away. We put those patients on Heartgard. This will keep them from getting many more heartworms, and is unlikely to cause a problem. At least you are “holding the line”.

    While it would be better to clear the dog, I wouldn’t have problems with holding the line until you are able to. If the dog feels okay, I cannot see any reason to euthanize at this point.

    We treat plenty of dogs who are outside while their owners go to work. Certainly 24-hour observation would be ideal, but it is almost never the case.

    It sounds like there is some failure to communicate here, either from the veterinarian to you, or from you to me.

    Please contact your veterinary hospital and ask to see your regular doctor. Share your concerns with him/her.

    Best wishes.

  102. Barb says:

    This is a great site. Helps to know that others are going through this. We adopted a male lab in January this year. When we took him to the vet, we found out that not only did he test HW+, but his previous owner knew that he tested HW+ in June 2009 and did nothing. Maddening.

    Here’s our update: we treated the 4 weeks of doxycycline to kill the wolfbachia. We also did a shot of invermectin. We did the first immiticide shot in February. Rather than do the 2nd/3rd shots after 30 days, our vet chose to wait at least 3 months. We used monthly Heartguard in between the treatments.

    Her line of thinking is that since the first Immiticide shot only kills adults, and the Heartguard only kills the microfalria, then we waited 3-4 months for any surviving baby heartworms to grow into adulthood. That way, all worms would be killed at all stages. Any worms that survived the 1st shot and made it to adulthood would be killed with the 2nd and 3rd shots.

    Have you heard of this process before? The vet was at a conference the week before my appointment, and said that this was presented. It does stretch out the healing process, but seems to possibly have a higher percentage kill rate.

    Anyway, we had shot #2 yesterday, and #3 this morning. I am just hoping and praying that we’ll get through the next critical time period as the worms die off.

    Any thoughts on this new 3-4 month approach? It makes sense to me, even if it does take more time.

  103. lynn says:

    Is doxycycline use recommended for dogs in all stages of heartworm? Is it now standard protocol to use this? My vet is not using it, and I’m just wondering in what situations it’s not indicated.

  104. Doc says:

    The use of doxycycline is widespread. Is it the standard of care? I don’t know that I could say that. It is recommended by the heartworm society researchers.

    While some dogs do not tolerate it, having nausea and so forth, most do well with it. It inhibits the Wohlbachia micro-organism which is beneficial to the heartworm. This causes the heartworms to become weaker (and more easily killed), and smaller (less to dissolve afterward).

    That being said, we treated thousands of dogs without it until the research recommending it was done.

    In most cases, I believe that it cannot hurt and that it probably helps a little. I haven’t done any controlled research, so I rely on those who have.

    Thanks for reading and writing.

  105. Doc says:

    Hello, Barb,

    The delay of three to four months would be important based on what time of year the dog is being treated. If you are already six months past the peak mosquito season, then everything that is going to develop is already developed.

    In my area, that peak is July and August. If I diagnose and start treatment in January, there is little use in waiting three months for the next treatment.

    If I am treating in September, then I certainly would finish treatment in January.

    It is a function of when the dog’s unprotected exposure to mosquitoes has taken place, and the time of year that treatment has begun.

    Clear as mud?

  106. lynn says:

    I read about people using the terms “weak positive” antigen test result or “strong positive” antigen result. Could you explain what that means? Does it have any bearing on diagnostic plan or treatment plan?


  107. Doc says:

    Theoretically, that would indicate smaller or larger worm burdens.

    In my opinion (and that of some bona fide experts, which I’m not), this is a qualitative test. Positive means yes, negative means no (or less than four adult female worms – false negative results can occur when worm burdens are this low).

    I do not feel that you can make a meaningful determination of the number of worms from how “strong” the test result is. It’s a color change, like a pregnancy test. “How pregnant are you?”

    I make my estimate of worm burden based on the number of unprotected months of mosquito exposure, age of the dog, and whether there are any outward clinical signs of disease (as opposed to just a blood test result).

    Chest X-rays will show changes in the pulmonary arteries, lungs and heart size.

    For what it’s worth, my opinion is that the usefulness of the blood test is just “yes or no”.

    If it turns up “yes” when I don’t think it should, then we draw another blood sample and send it out to an outside reference lab to double-check.

    Thanks for reading and writing.

  108. Jodi says:

    Our newly adopted pup (a German Shepherd– approximately 2 years of age and 55 lbs) just completed her Heartworm treatment two weeks ago, the day before we adopted her.

    She is not yet spayed (and delivered a litter at some point in her young life) and we’re getting conflicting advice from two different veterinarians regarding when it is safe to spay her. Our vet is willing to spay her 6-8 weeks post treatment, the vet that the rescue uses (and administered her heartworm treatment) suggests waiting six months before spay.

    I’d like to be conservative and ensure that all of the dead worms have cleared her system before subjecting her to surgery but I also don’t want her to unnecessarily go into heat either (that said, our other two dogs are spayed females and she doesn’t have access to any male dogs so pregnancy isn’t an issue.)

    Thank you for your website, it’s been immeasurably helpful!

  109. Doc says:

    Hello, Jodi,

    The physical bulk of the dead adult heartworms should be totally dissolved by 5 to 6 weeks post treatment.

    Theoretically, this means that you have no more risk than a dog who never had heartworms by the time you get to the six-week mark.

    However, there may be weakened pulmonary arteries as a result of the downstream movement of dead worms and partial blockages that result. These weakened areas are more susceptible to breaking and bleeding under stress.

    This accounts for dogs who get the go-ahead for return to normal activity, and have a bleed when they start exercising again. This is rare, but it does happen occasionally (like, for me, 6 times in 30 years).

    This would be more a factor in exercise than in anesthesia, in my opinion.

    Six months sounds like an arbitrary figure, but if the dog isn’t healed by then, it probably never will be.

    At six weeks, you’ve just gotten rid of all the chunks of worm, so you could conceivably have some need to heal.

    I have spayed heartworm positive dogs because there was a strong risk of unwanted pregnancy, which would be a mess in the situation they were in. If the dog seems healthy otherwise, I am okay with this. Of course, this is in a dog that I am actually seeing and examining (which I cannot do with yours).

    You make a risk versus benefit decision with anything you do.

    Since you can prevent exposure to the male, I’d have a tendency to wait at least till three months post treatment. My bias, based on experience, may be nothing more than my own prejudice. There’s a lot of gray area here.

    Good luck.

  110. lynn says:

    Can heartworm lead to hair loss? Or can the preventative Interceptor cause hair loss? Since he’s recently adopted, I’m not sure what’s typical shedding for my dog (Chow-Corgi) for this time of year. Near his hind quarters, his hair is coming out in chunks. He is otherwise showing no clinical signs.

  111. Janet Evans says:

    Dear Dr,
    I am the very proud mother of the best dog in the world (sorry you other mothers…) named Riley who is a Lab Mix I got from the pound 7.5 years ago. He had a rocky start, getting an auto-immune disease when he was about a year old and went on/off prednisone a handful of times over the next few years, seeming to need smaller doses for less time during each flair-up. The vet seemed very sad that first episode and appeared to strongly be preparing me for the realization that Riley would be living a short and troubled life – but my priceless companion has been auto-immune-disease-free for about 4 years now (it went away? is that possible?) Plus he has a number of “lumps-and-bumps” now that the vet says are just fat-based fluid-filled sacks that come with age and are not-pretty but also not-harmful. The lump on his side is the size of a good grapefruit.
    He went to the vet 2 months ago for poor exercise tolerance and she ran a barrage of blood tests (all good) and felt it was probably arthritis, giving him some nutritional supplements. He went again last night for the gradual onset of panting in addition to the exercise intolerance and she ran tests to find he is positive for HW. He is not coughing. We are awaiting the “confirmation test” that should be back in 10 days before starting treatment. She X-rayed him and saw “a good-sized round mass in-between his heart and his lungs which could be the worms or could also be a tumor.” She saw it on one view but not on the other. He tested negative for HW 8 months ago (November) so, I assume with no mosquitoes in Ohio in the winter months, got this 3-4 months ago at the most.
    You are truly an angel here on Earth for answering questions and I know God will find a place for you some day… A couple of questions that I have: Is it that “confirmation” lab test that is sent out that tells me what “Stage” Riley is in? Is it a good sign that he has not yet developed a cough? Do tumors and worms look alike on an X-ray? Does his health history complicate his ability to go through the usual HW protocol you describe so thoughtfully? Do you think my best friend can do this? It will break my heart to an extent I can’t describe to lose him (I might die with him) but above all else I don’t want him to suffer.
    Bless you for your precious time.

  112. Doc says:

    Hello, Lynn,

    I have not seen hair loss associated with either the heartworm disease or with the oral preventives. Sometimes there is a spot of hair loss where topical preventives are applied (such as Revolution or Advantage Multi).

    I would be looking elsewhere for the cause of the hair loss.

    Sorry about the late reply. I was out of the country for two weeks visiting my daughter who is a Peace Corps volunteer in Zambia. We had not seen her for 17 months.

  113. Doc says:

    Hello, Janet,

    A really enlarged pulmonary artery trunk looks almost like a growth on the side of the heart base when you look at the X-ray from the ventro-dorsal view (dog lying on back, X-rayed from the underside of the chest). This is called “pulmonary knob” by some folks.

    While it is possible that your previous heartworm test was a false negative (fewer than four worms can certainly be missed on the test), I would think that at least the dog wouldn’t have had much of a worm burden. Thus, it seems very unlikely to me that a dog in that condition would develop a huge pulmonary artery in such a short period of time. This makes me very concerned that there is a mass of some kind in the chest.

    The confirmation test is a more sensitive test for the presence of the adult heartworm protein. Commercial laboratories give us “quality control” when we don’t believe our own results. It is basically just a “yes or no” test, though.

    It would not tell you anything about the dog’s health, other than whether or not heartworms are present. Small numbers of heartworms generally are quite well tolerated, causing no changes in the dog’s health or appearance (incredibly enough).

    In other words, if a dog with one heartworm is coughing, he is coughing for some other reason.

    Dogs with a history of auto-immune disease can have a relapse triggered by any major illness or event. So it is theoretically possible that going through the heartworm treatment could do that. I really don’t have specific experience or expertise in that particular situation.

    I am certainly not able to make specific recommendations for your dog. Your veterinarian knows your dog and has seen the tests and X-rays, and is the best person to advise you.

    That being said, your description does not put heartworms very high on my list as the cause of this dog’s “ain’t doing right” condition.

    If nothing else turns up, you might ask your veterinarian about referral to an internal medicine specialist.

    Good luck.

  114. lynn says:

    Thanks, Doc,

    Another question: can the ingredient in Interceptor cause drowsiness or vomiting in some dogs? Just gave him month number 3 dose of Interceptor a few days ago and he seemed to get really drowsy, his eyes weren’t as wide and bright; just didn’t seem to feel good, he vomited 9 hours later. Last month’s dose was given with Benadryl, which causes drowsiness anyway, this last dose was not given with Benadryl. He did have a reaction (vomiting, increased respiratory rate) 2 1/2 hours after his first dose (in hospital). The vet said this reaction happened earlier than in most dogs. I’m wondering if he could be sensitive to the ingredient and if it would be better to switch to another product, and what is the protocol for switching products?

  115. Doc says:

    Hello, Lynn,

    There are some specialists who prefer not to give Interceptor to dogs who already have heartworms, particularly if they have circulating microfilariae (baby heartworms).

    I have had numerous dogs who became positive while taking Interceptor, and I allowed them to keep taking it with no problems.

    However, if there seems to be a problem every time you give it, I would ask your veterinarian about switching to Heartgard, at least temporarily. That seems to be less of a problem for dogs that have heartworms already (at least in some cases).

    It would be worth a try.

    Share your concerns with your veterinarian.

  116. lynn says:

    Thanks again for the info. I have shared my concerns with the vet; the vet would like to keep him on the Interceptor and monitor his reactions for now because of the resistance of the Heartgard. I didn’t realize that the resistance issue was specific to Heartgard. Can you explain this? Because its been around longer? Used more? Does this seem to be the case all over or specific to the southern regions?

    Another vet pointed out that the dogs hair loss was of no concern; just shedding his undercoat. Difficult to know what’s normal with a very recent adoptee coinciding with very recent diagnosis.

    I just got the dog back two days ago from injection 1. He seems to be doing well.

    Awhile back you mentioned the importance of putting pressure on the injection site to avoid infection. A vet friend in Atlanta who sees far more cases than AZ, told me to make sure that the injection site gets shaved before administering the injection. He’s seen some bad secondary infections from dogs who were not shaved at the site. I just wanted to pass that along for everyone else about to go through injections now or when the immiticide becomes available to you. My dog was shaved and the injection site looks great, no swelling or redness. He’s on tramadol for pain, and is only exhibiting mild soreness.

  117. Doc says:

    Hello, Lynn,

    In my practice I have seen about the same rate of failure percentage-wise with Heartgard, Interceptor, and Revolution. I had more dogs on Interceptor, so I had more failures with Interceptor. The percentage was the same.

  118. Carmel Hunt says:

    Hi. I have a 12 year old mixed breed who has been on Heartguard preventative most of his life. Unfortunately, he recently tested positive for heartworms. We live in the South, and he is an outside dog. Anyway, the vet said because of his age and the expense that we should just give him prednisone, doxcycline, and sentinel, and that he would eventually suffer from congestive heart failure. Will this regimen even help? What exactly will it do? What is the pattern of treatment? The vet mentioned to give him the prednisone alternating months. What do you recommend for the frequency of these meds?

  119. Gina Downs says:

    Had our cocker spaniel treated 5 hours ago with his first shot.
    For the past 5 hours, he can not get comfortable, fidgets, lays in unusual positions.
    When walking, his right rear leg is toeing-in and his walks clumsily, often positioning that right foot too far under his body.
    In just the last hour, he has started some toe-dragging with that right foot. Not severe, and he corrects upon moving further into the stepping process.
    Also, he has started to drool excessively. Both ears are wet as if he drank from a flat bowl.
    Have given him 2.5 mg Diazepam to try to make him more comfortable.
    Forgot to mention … the vet had to stick him twice unsuccessfully and then changed needles and successfully administered on the third try.
    Do you think he is just experiencing more pain than usual because of the three ‘sticks’ at the site, or should we be concerned that something else is going on?

  120. Doc says:

    Hello, Gina,

    Please call your veterinarian and let him/her know what is happening.

    The medicine in the treatment (Immiticide) can cause a lot of inflammation at the injection site. This can occur no matter how smoothly things go and how little it seems to bother the dog at the time.

    This can range from being absolutely undetectable to a dog that is crying constantly with pain. Diazepam helps with anxiety, but has no pain relieving properties to speak of.

    Please contact your veterinarian about this, as human 0ver-the-counter products can be harmful to your dog. However, it sounds very much like your dog needs pain medication.

    The pain usually subsides in a couple of days, and most dogs don’t have this type of reaction, but the ones that do get painful do need some help.

    The difficulty in walking may indicate that the inflammation is causing enough swelling to put some pressure on a nerve root.

    Call your veterinarian and report this situation.

    Best wishes.

  121. Gina Downs says:

    Thank you so much.
    We did call our vet and he said to give Ecotrin low dosage. We did and our cocker finally got comfortable.
    This morning, he is walking fine and is almost as merry as usual.
    Unfortunately, we have to have the second shot administered in another hour or so.
    I want to choke the irresponsible owner who failed to give this fabulous dog heartworm preventative. In fact, ANY owner who doesn’t take this disease seriously. Don’t wait to see first hand how painful the ‘cure’ can be, you can’t imagine the pathetic, helpless look your dog adopts when under this kind of stressful treatment.
    GIVE THE PREVENTATIVE and GET SERIOUS about giving it according to protocol.

    Thank you, doctor, for listening and giving valuable advice.

  122. April says:

    I have a 6 year old Golden Retriever mix that I adopted from a local animal shelter three years ago. They were a small, low budget operation and since he was already neutered when his previous owners surrendered him the shelter signed him over for free. He seemed very vibrant and healthy so we opted to use Southern Agriculture’s walk in vaccination clinic to get his shots, but unfortunately did not get a comprehensive medical exam. The following year we scheduled Tanner for follow up shots and a full exam because his breathing had become noticeably quick and labored and he seemed to have trouble getting comfortable and would roam and switch locations several times before settling and going to sleep. He tested positive for heartworms, and his chest X-ray showed significant signs of infection. Dr. Poteet put him on Doxycycline and Heartguard, and Prednisone I think, and a few weeks later he started the Immiticide injections. Shortly after the final round of shots my husband and I went through a bankruptcy and divorced. I took Tanner with me when I relocated, and have just recently been in the financial position to start taking him to the local vet. It’s been a little over a year and his recent bloodscreen tested negative for heartworms. She said everything looked good, but I am still concerned because his breathing is still fast and heavy, and he now gags and coughs, sometimes vomiting clear liquid. The only thing the vet found was a yeast/bacterial infection in his ear which has been treated and since gone away. Should I be concerned about the breathing and gagging? He just doesn’t seem comfortable and I can hear him breathing from across the room. He will take several rapid breaths and then pause, wheeze as if he is straining, and then let out a heavy sigh before continuing with the same pattern. He also has excessive thirst. It’s not unusual for me to fill his indoor bowl two to three times a night after I’ve gotten home from work. Are these symptoms normal after heartworm treatment, or are they totally unrelated? Any advice or insight would be greatly appreciated!

  123. Doc says:

    Hello, April,

    Those are not normal findings after a heartworm treatment.

    If I were seeing a dog with this description, I’d be doing a complete blood count, Biochemistry panel, and chest X-rays.

    You should share your concerns with your veterinarian who is actually seeing your dog.

    When they don’t hear from you, they assume that things are going well.

    Get in communication with your veterinarian and tell him/her that things are getting worse and that you are worried.

    Good luck.

  124. Michael says:

    I have a 10 year old Siberian Husky who recently tested for mild/severe case of Heartworms. He’s presently going through the treatment process (shots completed 15 days post now) and is feeling and eating better, but my question is regarding his leg. A couple days ago his leg grew to about double it’s normal size and vet put him on furosemide for pitting edema. The vet stated that its a sign that his body is working hard to fight off the worms and it is a good and bad sign, is this true? How concerned should I be right now about his kidney failure. I understand his age is not on his side right now. We just moved to this town so trust in my vet is not at 100%. Thank you for your time!

  125. Doc says:

    Hello, Michael,

    When heartworms die and break up, the pieces can block blood vessels. This is generally in the lungs. The inflammation involved in the process could certainly cause a blood clot to form somewhere else.

    It is not common to see a leg swell after treatment.

    I feel sure that your veterinarian is using a safe dose of furosemide (a diuretic, generic for Lasix), so I wouldn’t be too worried about the kidneys on that account.

    If the leg swelling does not go down rapidly, be sure to tell your veterinarian. Just because your dog has been treated for heartworms, this does not mean he cannot have other diseases.

    Usually a big leg means a swollen lymph node that won’t let fluid drain. It can also be an infection in the leg itself, or inflammation from some other cause.

    Be sure to keep your veterinarian informed of your dog’s progress.

    Good luck.

  126. lynn says:

    My dog is 8-9 weeks post immiticide treatment. My vet had scheduled an 8 week check-up and I was told it was to be for a HW antigen test.

    I moved to another state. Just had the dog tested at the new vet 8 weeks post immiticide treatment. The vet drew blood, came back about 10 min. later and said he was negative. Great!

    Just got a call from the vet that although the test was negative, he went back and looked again afterward and he saw small traces of antigen and wants to test again and have it sent to a lab.

    Can you guess how this may have happened? Can a Snap test change from negative to positive?

    Is 8 weeks too soon to do a SNAP test? What is the recommended schedule for testing to see if the worms have cleared?

    Should I be keeping the dog exercise restricted (no hiking with me)until he tests negative?

    I don’t use “blessing” very often, but your blog has been a blessing during this long ordeal.

    Thank you for your time!


  127. Doc says:

    Hello, Lynn,

    At 8 weeks post Immiticide treatment, we would not expect any physical chunks of worm to still be present. Thus, a gradual return to normal activity is what we usually recommend at this point.

    Even though there are no “chunks” of worm left, there can still be heartworm protein (antigen) circulating in a dissolved form in the blood stream for four to six months after the Immiticide.(This is per Dr. Ron Blagburn, heartworm researcher at Auburn University).

    We routinely test at four months post-Immiticide, but if the dog were still antigen positive at that point, I would test again two months later.

    Bear in mind that the antigen test often gives false negative results if there are fewer than four adult female worms in the dog’s body. It is possible to have a negative antigen test and still have a small number of worms that have escaped death in the treatment. This is unusual, but possible.

    From your description of your situation, I would ask your veterinarian about delaying the follow-up test until four months post-Immiticide.

  128. Doc says:

    Hello, Lara,

    We generally send our patients home with prednisone for the inflammation in the pulmonary arteries.

    Most patients only have pain at the injection site for a couple of days, if at all (most dogs do not seem bothered, but some are very painful). We generally use tramadol for pain in these cases.

    You should call your veterinarian and let them know you are having problems.

    Good luck.

  129. Charles says:

    Hi Doc,
    I have a 5 year old Rottweiler who has completed his heartworm treatment but is continuing to lose weight despite my increasing his food intake, I have already wormed him with Pancur. What else could be causing his weight loss? He was 105 before treatment now he weighs just 80.

  130. Doc says:

    Hello, Charles,

    This is not expected with the heartworm treatment. The weight loss should be worked up as though the heartworm treatment had never happened.

    If stool exams are negative (and the panacur was a good start), the next step for me would be screening bloodwork – CBC, chemistry panel, thyroid.

    Nothing there, then imaging of the chest and abdomen.

    I think it is very unlikely that this related to the heartworm treatment. Immiticide could be toxic to the liver, but that is a very rare event. The bloodwork would indicate liver damage.

    Routine blood tests won’t tell you about liver function. There are other tests for that, like bile acids. The liver assembles what you eat into a form that can be used or stored.

    Weight loss is either:
    1. no access to proper food
    2. inability to digest food
    3. inability to absorb nutrients from the gut into the bloodstream
    4. inability to utilize the food (liver disease or diabetes, for instance)
    5. nutrients being consumed by parasites
    6. nutrients being consumed by fast-growing cancer cells
    7. nutrients being lost via kidney or gut damage

    You need to take this guy back to your veterinarian.

    Good luck.

  131. Cindy says:

    My 14 1/2 yo flat coat retriever rescue was cured of heartworms about 12 years ago. I am curious as to whether this condition/treatment many years ago could have resulted in some damage and is a reason for his rapid breathing, at this senior age. We realize he is old, has arthritis and likely CUshings (I.e. almost constant panting). He is now on tramadol, about 1 wk on novifit so far. Blood test did not show any unusually high readings, negative for parasites in stool. No heart or other problems during examination. Due to his age and how stressed he gets when we see the vet we are reluctant to run too many tests, and would not want to put him on the drugs for cushings. He is due for an ultrasound in a couple of wks. It is difficult to tell if this almost constant rapid breathing (about 64 breaths a minute)even when sleeping is because he is in pain. His gums have always been a light pink. His appetite is good as well as his bodily functions. He does seem to tire easily on the way back from a walk and can get wobbly. He continues monthly iverhart max. We just want him to be as comfortable as possible, and seeing him decline is heartbreaking. We have the highest confidence in our vet. Could his heart or lungs be functioning at a diminished capacity because of heartworms at an early age?

  132. Doc says:

    Hello, Cindy,

    I think this is unlikely to be a major component of your dog’s problem. If he had suffered much heart and lung damage at the time, he probably wouldn’t have survived to be 14&1/2 years old.

    I understand your concern about stressing him with diagnostic procedures, but they may allow for a treatment that will improve his quality of life, if not actually extending it.

    Just keep sharing your concerns and observations with your veterinarian.

    Good luck, and thanks for reading and writing.

  133. A Facebook User says:

    Thank you for this blog and the concise, well-communicated information. Would you please help clarify my dog’s situation for me? She appears to be a long-haired Chihuahua, adopted from the shelter on January 12. On January 4, the shelter listed her as HW positive based on the IDEXX test. They “aged” her at about six months and she weighs about 8.5 pounds; she was spayed January 9. She came home with five days worth of doxycycline.On January 13, we took her to our vet, who did a HW panel, which also came back positive. She had two views shot on January 19, which came back completely normal, and no microfilariae were detected. Also, the vet estimated her age at 8 months rather than six months. We continued the doxycycline for three weeks, then she got her first injection of Immiticide on February 3. We were told at that point that she would need her second injection in 30 days, and no continued doxycycline. however, I see that you mention two injections in 24 hours as standard protocol. On top of all this, my father died on January 15, and I’ve been preoccupied with all that entails, and now I’m confused about the right treatment for Josie, not to mention the challenge of keeping a very friendly, very happy, apparently otherwise very healthy young dog quiet! Oh, and congratulations on your daughter’s Peace Corps work – very impressive.

  134. Doc says:

    Hello, Facebook User,

    Since heartworms take six months to develop to a detectable stage, we know that your dog is older than six months (though we don’t know how much older).

    The normal appearing chest X-rays and the very young age of the dog mean we are probably dealing with very few worms. This makes the prognosis pretty good.

    Very small dogs can have problems with very small numbers of worms, simply because they don’t have much room for the worms to get clogged up in. Two worms in a tiny dog take up a lot more of the pulmonary artery volume than ten worms in a huge dog.

    The effect of the four weeks of doxycycline can last for up to 3 months, so that’s why you aren’t taking it again.

    I suspect that if you simply ask your veterinarian about it, they really are planning to do two injections when you return. I suspect this is just a little glitch in communication, as it sounds as though your doctor is doing a great job for you.

    Always ask your veterinarian when you have questions. We are often so sure that we are great communicators, and don’t realize we have not fully succeeded in that area.

    We would much rather you’d keep asking until you are satisfied that you understand the answers.

    As far as keeping the dog quiet, we just try not to encourage any strenuous exercise. It is not desirable to keep the dog in a cage for two months.

    The exception would be a dog who is having noticeable complications, and then we often do confine them to cage rest until those complications resolve.

    Thanks for the kudos to my daughter. She is happy in her work, and that makes me feel like a parent who didn’t screw up too badly.

    Thanks for reading and writing. Don’t forget to call your veterinarian with your questions.

  135. karen brown says:

    I was wondering if the worms inside the heart produce more babys. Or if the larvae only comes in through the blood stream via a misquito bite??

  136. Doc says:

    Hello, Karen,

    Oddly enough, the answer to both of your questions is YES.

    The adults in the heart do produce babies that circulate in the bloodstream (microfilariae).

    These babies are like Peter Pan – they never grow up.

    Babies that are sucked out of the dog by a mosquito undergo a change inside the mosquito. Then they ARE capable of growing up when the mosquito transmits them to another dog (or even back to the same dog).

    I couldn’t take blood from an infected dog and infect another dog, no matter how many babies were in the blood. The mosquito is not only a carrier, but an essential part of the parasite’s life cycle.

    Thanks for reading and writing.

  137. Holly says:


    I posted earlier on your site about my 6.5 lb. rescue Brussels Griffon going through heartworm treatment. I was worried she was too small to withstand treatment. I did treat her with Immiticide – 3 shot protocol and pretreated her with doxy. She did beautifully throughout the treatment and seems to feel so much better!

    I took her for her 6 month follow-up yesterday and I was told she is still showing as heartworm positive. As I’m sure you can understand, I am just sick about this. Was testing 6 months after treatment too early? Should I expect to put her through treatment yet again? What would you do in a case like this? I appreciate your input. My vet is out for the week so I’m in limbo here. Thank you again.

  138. Doc says:

    Hello, Holly,

    My concern would be about the timing of the treatment. Unfortunately, the period between infection by the mosquito and six months later is a period that we cannot detect the developing heartworms. For about four months of this period, the parasite is not susceptible to either the preventive or the Immiticide.

    It sounds like there were some developing heartworms at “just the wrong stage”.

    Sometimes we delay treatment until six months after the mosquito season for this reason. This is also why we want to continue (or start) heartworm preventive treatment even though we have diagnosed the presence of adult heartworms. We don’t want more developing.

    It is also possible that the Immiticide just wasn’t 100% effective. It is a sad fact that nothing is 100% effective 100% of the time.

    Your veterinarian is the person best equipped to discuss whether you should be undergoing Immiticide treatment again, or just re-testing in a few months.

    Thanks for reading and writing.

  139. martha says:


    Our little man just had his treatment last night. We were allowed to bing him home, and have him in his crate at all time except whe we take him out to do the restroom. Our problem is he is a marker and likes to run around before he does his business. Is there any way we can get him to go potty faster so he is not getting excited? He also hasn’t had a bowel movement in 24hrs which is not common.

  140. Doc says:

    Hello, Martha,

    I would just keep him on a short leash. If you walk around for quite a while, that should not be a problem.

    What we are trying to avoid is increased cardiac output and higher blood pressure.

    The dog is not going to stay comatose for weeks. We just limit his activity so that he cannot do aerobic exercise. We also try to avoid sudden bursts of vigorous activity.

    Getting a little excited is unavoidable, and I really wouldn’t worry about it. Just don’t let him run loose.

    Good luck.

  141. Ruthe says:

    My 3 year old “mutt” had the 2 dose tx for HW on may 5th. He still has an unusually large lump on his back that seems to be right on his spine. We took him back to the vet and she says that although it is not “normal” he is ok. No fever and still eating and drinking ok. He has had no coughing or shortness of breath. I am just concerned because it doesn’t seem to be going away. Today when I took him out his stool had a lot of mucus. Are these things I need to be concerned with and is there anything I can do?

    Thank you for your time and concern

  142. Doc says:

    Hello, Ruthe,

    A lot of mucus in the stool usually means some sort of irritation in the colon. This could be diet, eating garbage, intestinal worms, and so forth. I doubt it is related to the heartworm treatment. It would be good to take about a tablespoonful of a fresh stool (within 12 hours after it is passed) in for your veterinarian to check it.

    The lump on the back sounds like it could be an unusually severe reaction to the Immiticide injection. These are rare. Usually the swelling gradually goes down. I have had one several years ago that broke open and drained.

    I would ask your veterinarian if she would be willing to check the lump weekly.

    Good luck. Stay in close communication with your veterinarian.

  143. Scotti says:

    Hey Doc!

    Your blog is an awesome resource! I wish I had found it before I did the HW treatment in my rescue.

    I have a question about post-treatment. SD is a mix and tested high positive about a year ago when I found her. She had been positive for about 18 months before that (neglectful, undeserving former owners).

    We did her treatment at the end of March and she did about as well as expected. However, she seems to still have injection-site pain. It’s not constant, but sometimes when she’s running around she’ll cry out and tremble afterwards. I give her tramydol and in a day or so after the incident, she’s usually okay. Is it from the injections? She’s a 7 year old, 40 lb mix and did the 3 injection series. She had the most trouble with the pain and coughed very little.

  144. Doc says:

    Hello, Scotti,

    This is pretty unusual. I would let the veterinarian examine to see if there is a fluid pocket or something.

    Good luck.

  145. Jennifer Vickery Faust says:

    We rescued a Boxer over two years ago just after she was treated for Heartworms. For a few months after her treatment she had a cough, however it did eventually clear up. Now two years later she is starting to cough again. She is on regular heartworm meds and is an inside dog. This is her first summer in Arizona so I was wondering if that could be the problem or if we should be worried that she has hearworms again? Can you please help?

  146. Doc says:

    Hello, Jennifer,

    Even if the heartworm preventive has not been 100% effective, it is very unlikely that your dog would have acquired enough worms to cause illness. I highly recommend that you take her to your veterinarian to determine the cause of the cough.

  147. Laura Richards says:

    Hello! Thank you so much for your very informative and well written blog! I am with a pet rescue. We rescue many dogs that test positive for heartworms and I am always researching to find the latest information as well as what various vet hospitals are recommending. I hear many rescues tell how they are using the “slow kill” method for asymptomatic heartworm positive dogs. ie using a monthly preventative or ivermectin vs the traditional Immiticide, both because of costs and many state that it is easier on the dog. Do you have an opinion on this? We are still using the standard Immiticide for almost all of our heartworm positives and have been lucky in rarely seeing any adverse reaction, most dogs seem to do very well following treatment.
    Most recently, we had two beagles come to the rescue. Both tested heartworm positive and both were treated with Immiticide about a month ago. After a few weeks of cage rest, we discovered that the female was pregnant, she was too early to tell when she was treated with Immiticide. There seems to be little information on the use or safety of Immiticide in pregnant dogs and we of course would have not treated her had we known she was pregnant. She is now a day or two from having pups, unfortunately, her breathing has become somewhat labored. X-rays are showing bronchitis which our main vet said is typical after a heartworm treatment. Her bloodwork is also showing high WBC, low HCT, low platelets, low calcium. We and the vet are unsure if a c-section would be easier on her or to let her have the pups. Just wondering if you have ever had experience with a similar situation?
    Thank you, love your blog!

  148. Doc says:

    Hello, Laura,

    I am happy to say that I have never had to deal with the difficult situation that you describe with this pregnant beagle. Your on-site veterinarian will be your best resource by far, here.

    The “slow kill” or “soft kill” is no longer recommended by the American Heartworm Society. The problem with treatment is the dead worms shifting position and floating downstream and creating blockages and inflammation. When you treat the dog with Immiticide, you can predict when this will occur and administer anti-inflammatory doses of prednisone and restrict the dog’s activity.

    Even if the heartworms do die with 2 years of ivermectin (or 3 or 4, and I have rechecked positive dogs year after year), you will not be able to predict the timing. Will you restrict the dog’s activity for 3 years?

    The only time that I do this is when I have an elderly patient with very few worms, or the effective Immiticide treatment is not possible, due to the owner’s financial circumstances.

    It is below the accepted standard of care.

  149. natasha lynn says:

    Is post treatment injection site swelling common? Our dog finished treatments about 3 weeks ago and is doing very well. Our only concern is a somewhat hard bump where they told us her injection site was. It was larger and has gone down. She shows no signs of pain or discomfort when we touch the area. She is a shepard mix around 2 yrs old who weighs about 42 lbs. She is a rescue that had heartworms before we adopted her.

  150. Doc says:

    Hello, Natasha,

    I would not say that swelling at the site is common, but it certainly does occur.

    The fact that it has decreased in size is good, and it will probably resolve completely after a few more weeks.

    I have had one patient that sloughed out a golf-ball sized area of tissue, like a terrible spider bite.

    Most patients experience very minimal swelling (if any), and that usually disappears within days.

    Your experience is not unique, but fortunately occurs in a small minority of patients.

    If you have not done so, you should let your veterinarian know about this.

  151. Karen Conley says:

    We have a 12 yr old Jack Russell Terrier who tested positive for Heartworm last week. The only symptom he had was that he lost 3 lbs –no coughing and energy level is normal. Our Vet started him on Heartguard, Doxy and Prednisone. The plan for treatment is to wait 3 months then start the Immiticide injections (one injection, then 2 more 24hrs appart one month later). X-rays showed a slightly enlarged heart,but not bad. Blood & urine were both normal and he said his Liver and Kidneys are fine. In your opinion, how do older dogs usually do with the Immiticide treatment? Also, is it normal to wait 3 months to start treatment, or would sooner be more beneficial? I appreciate any advice…thank you

  152. Doc says:

    Hello, Karen,

    The weight loss is unusual in a case like this, so one wonders if there is some other factor present that has not yet come to light, despite your veterinarian’s very thorough evaluation.

    The treatment that has been started sounds appropriate to me.

    I usually start the first Immiticide injection after one month of doxycycline. It is possible that your veterinarian has a specific reason for waiting longer. I would recommend that you discuss this with him/her, since you have questions.

    Generally speaking, the doctor seeing your pet is the one best equipped to answer your questions.

  153. Mary says:

    I adopted my dog a week ago. I was informed that he was HW positive, and that the shelter will cover the cost of treatments necessary. I took him to the vet yesterday, and was told that they will start treatment in 6 months. In the mean time, I am to give him 100 mg of doxycycline a day (50 mg every 12 hrs). I am unsure of how much exercise I should give himduring the 6 months before he gets his first shot of immiticide. Is this common? Should i cough up $200 and get an x-ray taken to be sure it isn’t advanced. He was tested positive on Sept 2, and the vet’s note says he’s a good candidate for adoption. He has a lot of energy, though he does well in his crate when I’m at work all day. I’m also concerned about his sneezing and stuffy nose (thickish mucus comes out of his nose when he sneezes). But what really worries me is, every hour or so he would stop and start breathing heavily, with his hind legs stretched out. It’s like he’s having trouble breathing. The vet told me to record this as it happens and email it to her. Are the sneezing, mucus, and heavy breathing related to the heartworms? Any help with my baby would be greatly appreciated! Thank you!

  154. Doc says:

    Hello, Mary,

    The mucus and sneezing are not likely to be related to the heartworms, and they may very well be related to the heavy breathing.

    I would be concerned that the dog has some other respiratory problem (an infection or even a foreign body up nose).

    Heartworms are more likely to cause poor endurance and coughing.

    If the dog were limping and were positive for heartworms, we would be looking elsewhere for the cause of the lameness. I would be looking elsewhere for the cause of this respiratory problem.

    Sneezing out snot is not normal and the dog needs to be examined. Go ahead and get your videos, too, but the doctor needs to see the dog.

    Waiting six months before the heartworm treatment is often done to be sure that any immature heartworms now present will be mature enough to be killed at treatment time. Otherwise, if you treat now, you may have to treat again later.

    In addition to the doxycycline treatment, the dog is usually put on preventive medicine, with Heartgard being considered the safest drug in this circumstance.

    It sounds like the veterinarian is being conscientious, but she is operating on the information that she has in hand. She needs to see the dog. Don’t forget the videos.

    Good luck.

  155. Jessie says:

    I adopted a dog last week from the Humane Society. The dog tested positive for HW. After contacting the clinic he was first admitted to by his previous owner, I found out he was Stage 3. The owner had given him heartworm preventative 8/27/12 and I started the injection treatment 9/20/12., two days after I adopted him.

    I am doing my best to keep him calm but I feel that I am just hurting him. When I am not home he is in the crate he cries or acts like he’s digging. And when arrive home, is super hyper and jumpy. Besides that he is always relatively calm.
    Everything seemed to be going fine until this evening when he started tremoring then vomiting clear mucus about 6 times. ONE of the times it contained specks of blood.

    He did not eat this evening and when I tried to pick him up,he yelped in pain. 2-3 hours later he is no longer tremoring and vomiting mucus.

    He was on tradamol from Thursday to Saturday evening. And is on predisone every other day. He has a pill Thursday and Saturday and will have one tomorrow morning.

    What is going on? Is this normal or are these severe complications?

  156. Doc says:

    Hello, Jessie,

    Sorry about the delay, but for some reason the comment feed didn’t get to my email like it’s supposed to.

    As you have probably already contacted your veterinarian (and if you haven’t, then DO), you know by now that this is certainly not “normal”.

    These are not the worst complications I have seen, but usually would require more aggressive treatment. I would have recommended restricting the dog’s movement (staying in the crate, or hand-walked on leash to eliminate) for several days. I would also have increased your prednisone dosage for a few days.

    It is important to let your veterinarian know what is going on and follow his/her recommendations.

  157. Jessie says:

    Thanks for getting back to me. I did contact my vet and he said though not normal that it is part of the process but if the vomiting mucus happens again to let them know. However, today he started having a cough every few hours.

    My dog is currently predisone every 48hours.

    Thanks for getting back to me.

  158. Nathan says:


    I recently noticed my dog’s ribs enlarging. The vet said he had Stage 3 heartworms. Could this enlargement be a sign the treatment is not working?

  159. Doc says:

    Hello, Nathan,

    Normally the size of the rib cage can’t change much. It is more likely to look different if something else is changing, like a shrunken or swollen belly, or so much weight loss that the ribs stick out.

    If your dog is being treated and his outward appearance has changed significantly, then something strange is going on. That is not to be expected.

    Time to get him back to you veterinarian for re-evaluation.

  160. victoria says:

    Hello, i adopted a wonderful dog from the spca. they told me she was 2 years old and was just recently tested positive with heart worms and that they were young and treatable with pills. i took her to 2 different vets and have paid already over $500 i can barely afford my own medication… i kept asking the vet questions about signs to look out for to know if she was about to go. he simply refused to give any sort of answer, so here i am unaware of what to look for. she has been getting worse. all he told me is that her heart and lungs are damaged from adult heart worms and that her intestines are pretty torn up as well. i do not know what to do. i do not know how badly she is suffering. because from everything i have been reading even with treatments that cost an arm and a leg, there will of course not be any way to fix her heart and lungs and intestines considering how damaged they are. she is always licking, and gagging. vomiting, hacking up foamy loogies, wheezing, breathing heavy, cant run like she used to without having to stop and cough or catch her breath. i just wish i had SOME sort of idea at least a little bit, of what to do. i can not handle having her go and me finding her or seeing it happen. i am not emotionally strong enough. ii am so torn up that the spca lied to me about her. i love her so much.

  161. Doc says:

    Hello, Victoria,

    I can appreciate you frustration. You wanted to give a home to a dog who needed one, so you went to the shelter.

    There isn’t a good way to reliably determine an adult dog’s age. You look at the dog’s overall condition, and particularly at the wear and condition of the teeth. You compare this to the appearance of the dogs whose age you know, and you try to fit the dog in somewhere. When the SPCA gave you an age, it was probably their best guess.

    The recent diagnosis may have referred to the fact that they just recently had the opportunity to test the dog.

    The blood tests for heartworm don’t tell us anything except “yes or no”. To look at the progress of the disease, they would have had to at least do chest X-rays, which the shelters typically will not be doing as part of a checkup if the dog is acting okay.

    Heartworm disease is progressive, so she might have acted pretty good at the shelter, but begun to deteriorate soon after adoption.

    If her condition is deteriorating rapidly, then the long-term prognosis is not good.

    While treatment to get rid of the worms will not heal the damaged heart, the lungs will get better when the worms are gone. Also, the damaged heart will have much less work to do, so the dog may be able to function pretty well when the worms are gone.

    The fact that she seems to be losing ground pretty fast is the troubling thing. She may not be able to last long enough to deal with the treatment and subsequent breakup of the dead worms.

    I am sorry that I do not have an easy answer for you. It sounds like your veterinarian is trying to be thorough, but that you guys are not communicating very well.

    Try putting your concerns and questions in writing and leaving them with your veterinarian. Keep asking until you feel like your questions are being answered.

  162. Aaron says:

    Our little 5yr old chihuahua/dachshund rescue pet just underwent her second injection after being diagnosed with later stage heartworms. My concern is that she has very high anxiety in specific situations. Tonight there is a thunderstorm, which means she is panting VERY heavily, and her breathing/heart rate is much increased. Her whole body shakes uncontrollably and nothing calms her. (Though she’s glued to my side all along). This is normal behavior for her during a storm, but I’m concerned about the risks caused by the increased blood flow. I don’t want to sedate her. Is there a very high risk for complications in these cases?! I just need to know the potential and which things I really should be worried about. Thank you for your time.

  163. Doc says:

    Hello, Aaron,
    I can appreciate your concern in this situation.

    While the dog’s heart rate is certainly elevated in a situation like this, I do not think that this is increasing your risks on the same level as aerobic exercise.

    I can appreciate also your reluctance to sedate the dog. There is an amino acid product (one of the building blocks of protein) called “Composure”. This is not specifically sedative, but provides relief for some dogs. It didn’t work for my own dog with thunderstorm anxiety, but several clients have had good results. It is inexpensive, has no side-effects, and is certainly worth a try.

    We have had some success with the Thundershirt product. It’s not total relief by any means, but definitely provides a measure of comfort to our dog during storms. The product is well-constructed and durable.

  164. vickie says:

    my dog was tested light positve for heart worms. i now have to make a decision to do slow kill or the shots. this is because the is very over weight and seven yrs. she eats half of what my other dog eats but doesnt lose wieght. she is in very good shape other wise, aleart no cough. if i didnt know her i wouldnt think she was seven. she is a very lazy dog always has been, but still playful when she decides to be active. my question is her weight and treatment together, i dont want to lose her. slow kill sounds like i could be taking her chances away though. help

  165. Doc says:

    Hello, Vickie,

    If by “slow kill” you mean just stayingon heatworm preventive for years, I have lost faith in that process, and the American Heartworm Society no longer endorses it.

    In the case of a geriatric patient, or one that might have trouble withstanding treatment for other reasons, it is reasonable to stay on preventive and “hold the line”.

    Has your dog’s thyroid level been checked? This is a simple blood test. That behavior is classic for low thyroid – poor activity and overweight, despite low food intake.

    Thyroid hormone governs the rate of metabolism. It’s really cool to see a hypothyroid dog wake up and come back to life on their hormone replacement (which is not expensive).

    Thanks for reading and writing.

  166. Linda Duke says:

    Hello Dr.
    we recently started a HW treatment rom a vet for a dog we adopted. She was in stage 3 HW condition. We did two immicticide injections a day apart and then 30 days later 2 more a day apart. About 3 weeks ago she started to show really bad skin lesions that bleed, crust up and then bleed again. they are on her neck head, stomach and back. lots of very small ones but the 2 on her back are about2″ now and the one goes almost around the backside of her neck. The vet keeps telling us this is her bodys way of expelling the worms but I havent been able to find anything online to that fact. We’ve had her on an antibiotic and on predisone and antiseptic baths and no improvement. Have you ever heard of this.

  167. Doc says:

    Hello, Linda,

    Since I have not seen your dog, I cannot really advise you on specifics here.

    This is certainly not an expected event following heartworm treatment.

    The only thing that I can think of is that it is either something completely unrelated, or that the dying worms have gotten the body’s defense system stirred up and you are having some sort of auto-immune skin disease (the body attacking itself).

    If the dog is not responding to treatments as expected, then it may be necessary to get a skin biopsy to determine what is causing the problem.

    Be sure to let your veterinarian know how your dog is responding (or not responding) to treatment. Sometimes we don’t see something for a few days, and the telephone call doesn’t really give us the true picture.

  168. Sherri says:

    We have a “young” boxer mix rescue who is five weeks past his final immiticide injection. He has one more week of prednisone every other day. He only had one slight complication where coughing occured and the vet increased his predisone for a 3 day period and an additional 2 wks of Doxy. This was about 10 days post final shot. The vet took x-rays at that time and saw some irritation in the lungs and his heart was a bit enlarged. My question is at what point should ask the vet to repeat those x-rays? I would like to know if the “damage” is healing and the heart has returned to a normal size. I was thinking I would ask at his hw re-test. Thank you for your helpful information.

  169. Doc says:

    Hello, Sherri,
    Sounds like this is about 3 weeks after the previous X-ray.

    We usually recommend restricted activity for 5 to 6 weeks after the last Immiticide injection. At this point the worms should be pretty well dissolved, that is no big chunks left (though there may still be circulating heartworm protein that will still give a positive blood test).

    I have had a very small number of dogs who seemed fine at this point, but had some damage that didn’t show until the dog was stressed by returning to exercise. These dogs may cough quite a bit, or even cough up blood. They don’t usually have severe problems at this point.

    I think it’s a good idea to talk to your veterinarian about repeating the X-ray when you go back. He/she will also be listening to the dog’s chest to evaluate the heart and lungs.

    You will want the return to activity to be gradual and supervised. Talk with your veterinarian about his/her recommendations.

  170. meg yarmel says:

    Hi Dr.

    Interested in adopting 6 yr old dog(s) with former HR and cure. What tests would you recommend to determine their present health status? Would it be cost prohibitive? Can one expect heart and lung problems down the road that would require testing and tx?

  171. Doc says:

    Hello, Meg,

    I would start with a good physical exam and current heartworm test.

    A chest X-ray would be the most informative as to whether there has been damage “along the way”.

    I don’t think that this would be cost prohibitive.

    If that all looks good, then I would not expect unusual problems in the future.

  172. Bethany says:

    Just wanted to comment because I am into rescue and fostering and have dealt with many cases of dogs coming to me with heartworms in south Louisiana (I actually have a yellow lab rescue foster that just got his second treatment shot today)…if possible of course it is ideal to find out a dogs heartworm status before adopting but I would hate to see all of the dogs down here in shelters that test heartworm positive get overlooked and put down (and down here unfortunately they get put down very quickly if no one steps up due to the immense overpopulation). As the dr mentioned there are pros and cons to undergoing the expensive and intense heartworm treatment versus just keeping them on monthly preventative and allowing the current ones to die in time. I have been through both methods with rescues and have always had vets only recommend the latter option if it is not an advanced case (and very often it is not advanced especially in young dogs). Anyway I guess my point is that the option of just continuing preventative in a heartworm positive dog- while maybe not always the most ideal- is cheap and in my opinion better than letting a dog be put down in the shelter because you cant afford the thousand for the fast treatment. So don’t necessarily pass up on a good dog just because of heartworms everyone!
    Thanks for this blog it is very informative!
    PS I have also been hearing more and more about cases of dogs that are on monthly preventive contracting heartworms as you mentioned. It seems to be becoming somewhat of a problem in Louisiana. Yikes!

  173. Doc says:

    Hello, Bethany,

    Thanks for taking the time to make your thoughtful post here.

    While we have been having fewer problems in our area with the “lack of efficacy”, when I talk to people south of us, the problem hasn’t gone away for them.

  174. debbie bullard says:

    I have a rescue that was treated for heartworm and her hacking was only procucing a small about of phlegm and today she has a little bit of blood in it.
    She is due back on the 11th of this month.
    Should she be seen as soon as possible?

  175. Doc says:

    Hello, Debbie,

    With blood being present, I would not wait until the 11th. Do call your veterinarian and inform them. If she were my patient I would want to see her as soon as I could.

  176. Holly says:


    I wrote to you some time back about my 6 lb Brussels Griffon rescue with heart worms. We treated her and she failed treatment. She subsequently suffered a PE and was hospitalized. We put her on Plavix and were waiting for to stabilize before retreating. She then suffered a stroke but thankfully recovered. Then she had a second one a week after the first! She finally tested negative for heart worms after the first stroke but we are puzzled as to why she is still throwing clots despite being negative and on Plavix. Could this still be an inflammatory response to the heart worms despite now being negative? We are testing for Cushing’s despite the fact that she has no other symptoms. Thank you for your help!

  177. Allison says:

    Hello Doc~First I just want to say I have been reading your blog for the past couple of hours, while my new foster Fiona sleeps on my arm on the floor. Thank you so very much for all the invaluable HW information. I love my vet but I am one of those pet mommies that ask a million questions so to have you to run this by is great! OK, so miss Fiona (Florida native) had her 2 injections Monday and Tuesday. Was doing pretty well until this morning. Her lethargy is greatly increased. No coughing, normal amount of panting, and sleeping comfortably (except for her snoring). Her eating and drinking is very much off today, tail is just hanging and when I walk her around my yard she doesn’t even put her nose to the ground. She pooped normally but doesn’t squat to pee. The vet has her on doxy now (she had it for URI in Florida but had finished it before coming up to NJ) but not for the entire month prior to treatment. He didn’t give me prednisone, but did say to give half a buffered aspirin once a day (she is 55 lbs) Would she be more comfortable taking something stronger? Seems half an aspirin at her weight would not do a lot to ease any inflammation. Also, is increased lethargy a few days after treatment to be expected? I know not every dog has the same effects, but don’t want to run her back to the vet if it’s to be expected. Thanks so much for all your help 🙂

  178. Doc says:

    Hello, Allison,

    Buffered aspirin doesn’t really protect the stomach. The stomach acid is much more powerful than the acidity of the aspirin.

    Aspirin causes two problems. With chronic administration, it inhibits platelet function, which makes you a free bleeder. That doesn’t happen with occasional use.

    It is anti-secretory, so when it hits the stomach lining, it interrupts the production of the protective mucus that coats the stomach lining. This allows the stomach acid to damage the lining. I am told that we lose 1/4 tsp to one teaspoon of blood for every regular strength aspirin we take.

    This is why enteric coated aspirin (like Ecotrin) is used by heart patients who take one every day. This inhibits platelet function, reducing the risk of clots, and it doesn’t dissolve until it gets past the stomach.

    Cutting one in half would remove the coating, so people often use the lower strength tablet and take as many as needed (like one to two 81mg “baby aspirin” strength).

    There was a period of time about 30 years ago when the American Heartworm Society was recommending daily aspirin during the post treatment period, but this was later shown to be unhelpful, and the recommendation was changed.

    I am not in a position to prescribe for your dog. I personally have had much better luck with corticosteroids like prednisone following Immiticide therapy.

    If you are in New Jersey, it is likely that your veterinarian doesn’t see a lot of heartworm disease, compared to an endemic area like the Gulf coast or the Mississippi valley.

    This doesn’t mean that he has no idea how to treat it. It does mean that he needs feedback from you on how the dog is doing. Since the dog appears to be having complications from the movement of the worms, he needs to know that.

    With new information, he may give you a new recommendation. If he doesn’t hear from you, he will assume that all is well. All is not well.

  179. Allison says:

    Hi again Doc. I had spoken to my vet before I posted my first question and he didn’t seem overly concerned, but when Fiona had trouble standing a few hours later I called again and the vet had me come and get a few Deramaxx and says give half a pill once a day. Assume this is treating pain only, seems they think her lethargy is due to pain from the injections. They did take a while listening to my concerns so I feel they are well informed of how she is doing. Should I request a steroid also? Thanks again.

  180. Doc says:

    Hello, Allison,

    You cannot combine these drugs. It is important that you don’t add different NSAIDs together.

    Deramaxx is anti-inflammatory as well as a pain reliever. It is really effective for musculo-skeletal pain and inflammation. If your problem is indeed soreness at the injection site, this should really help. My experience with injection site pain is that it usually subsides within 3 days after the injection.

    If the problem is inflammation in the pulmonary arteries, then the Deramaxx may not work as well as the steroids.

    You cannot combine the Deramaxx with steroids. The two together can cause serious stomach bleeds.

    Keep your veterinarian posted as to how the dog is doing.

  181. Allison says:

    OK Doc, she perked up with the Deramaxx. Went outside with raised tail to potty and ate most of her dinner. Still moving slower but a definite improvement from earlier today. Didn’t mean to misspeak, I do know to never mix the 2 drugs I mentioned. I should have said steroids INSTEAD of the nsaid. Thanks for the prompt responses, very much appreciated. I will absolutely keep my vet informed 🙂

  182. Heidi says:

    Firstly, thank you for taking the time to do this blog, like others i found this late at night while trying to figure out how to help my distressed dog. We have a rescue yorkie who had his first treatment about 10 days ago. I did not crate him due to him getting overly upset when I put him in and took him out, I figured it was less stress on him to simply keep him out in a confined area with my older dog. Tonight he has been wretching and doing a deep cough maybe 6 times or so. I’ve managed to keep him close and relatively still. And intend to take him back to the vet tomorrow, as something definitely seems to have shifted. My vet did recommend Benadryl to help slow him down and to help with him biting on hs feet (we think it an allergy that just started). Hes been taking about 6mg the last few days and it seems to have helped with the biting. My question is can prednisone be used with Benadryl I’m hoping he will be prescribed this again tomorrow to help with his breathing.

  183. Doc says:


    Sorry I didn’t see this until late this evening.

    I’m sure that your veterinarian has told you already that prednisone and benadryl or okay together.

    I hope things are going okay. Very small dogs can have more severe problems with the breakup of the dead worms. It’s just the fact that there isn’t as much room for the worms in a small dog’s arteries.

  184. Karlie says:

    I just would like to start off by saying thank you for sharing your wealth of knowledge with concerned readers like myself. My 7 year old adopted golden retriever was just diagnosed with heartworm last month. He was given his first shot of immiticide 6 days ago and given the second 24 hours later. He stayed overnight between injections. Upon returning home with him he seemed very restless and was panting heavily. I called the vet and was told to bring him back. She examined him and decided that it was probably just pain so she kept him overnight again to observe him and gave him a painkiller, I picked him up the following morning as he was doing better. He seemed a-ok for the next few days. I have not been crating him because he is not very active in the house just the occasional walk from room to room and when we go out we go potty and come right back in. This morning when I woke up I noticed two small puddles of was appeared to be foamy white phlegm with a yellow twinge to it no blood. I did not hear him cough it up. So back to the vet we went. She listened to his lungs and his heart and she said that everything sounded really good. She told me that she would like to hear from me if we notice any coughing, heavy breathing or abdominal breathing. So far I have seen none of these symptoms. I asked her how severe his infestation was and she wasn’t sure because the main vet there did his workup and she had not seen his x-rays or test results but she figures that it wasn’t terrible because they aren’t spacing out the treatments more and he wasn’t displaying any symptoms. That makes me feel better. Sorry to ramble on, I just wanted to give you some information about what was going on. My question is how likely is it that we will see complications like coughing and heavy breathing since now is about the time the worms are starting to die and shift and during what time frame do they usually occur in your experience? Have you seen any cases were dogs completed the treatments without having any of these problems? I want to add that he is receiving prednisone and antibiotics. I was also wondering during this style of “fast kill” treatment how soon do the worms begin to die? Do they die all at once or do they die a few at a time? Is it also common for a dog not to feel very well during this time? He seems a little out of sorts and not his usual chipper self today. But he perked right up during his field trip to the vet today 😉 But he is eating and drinking and has been chewing his rawhide. Again thank you for answering questions for your readers. I have a great vet and I will definitely continue to be in touch with them, I was just looking for your input.

  185. Doc says:

    Hello, Karlie,

    The worms usually start dying 4 or 5 days after treatment. I doubt they all die exactly simultaneously, but they pretty much all die within the same 24 to 48 hour period. Again, this is when we usually see signs of difficulty, such as those you describe.

    Your veterinarian has already prescribed what sounds like appropriate medication to me. Keeping activity to a minimum is important while the dog is showing these signs of distress.

    It is not uncommon for dogs to display the bad signs you have described, but most will come through the treatment okay. Keep the activity restricted, and keep in close touch with your veterinarian.

  186. Lara R says:

    Hi there
    My question is once the heartworms break up and go to the lungs how long does it take for them to break down?
    We had our 14 lb rat terrier/jackrussell treated 2 weeks ago. She started coughing/gagging Friday and the vet put her on prednisone 5 mg twice a day. By Sunday am she had laboured breathing, shaking when she breathes sometimes. The vet said there was not much to do but keep her quiet and keep on the prednisone.
    She is eating and drinking, is resting a lot on her own, gums are pink and good capillary return. Not restless and does appear somewhat interested in what is going on around her.
    I guess I just wonder how long before they disolve and she is feeling better. (I actually think it bothers me more than her, while she is not herself, she doesn’t apper to be in any distress)
    Thank you so much!

  187. Doc says:

    We generally consider that it will take 5 to 6 weeks after treatment before we are pretty sure there are no solid chunks of worm left. There will still be heartworm protein circulating in the blood at this point (so test is still positive), but nothing that should clog up a vessel.

    On rare occasions, a vessel damaged by the process will break when the dog returns to exercise. Return to exercise should be gradual, and monitored by you.

  188. Lara R says:

    Thank you. We took our dog back to the vets tuesday and her chest xray had changed, there is inflammation in her lungs. She got a shot of lasix, dexamethasone and some oxygen. The vet prescribed doxy as her lymph nodes in her neck were swollen. She remained with rapid shallow brathing and couldn’t seem to get comfortable friday, so the vet checked her again, no temp and he felt her lungs were much clearer (no wheeze or crackles), all signs pointed to no oxygen deprivation and despite wanting to stand all the time she looked brighter.
    Today, Saturday she is the same. Rapid breathing and unable to get comfortable to lay down. The Vet said it would be at least a week before we would see a change, do you think it will be longer? Because it takes 5-6 weeks before there are no solid chunks? Or do you think we will see her slowly get better as time passes?
    I really appreciate this blog, it was very helpful as was your response. That is why I came back!

  189. Doc says:

    Hello, Lara,

    I really cannot give you any specific advice here. Your veterinarian who is actually seeing your dog is your best source of information at this point.

    It is troubling that she still is having this much difficulty breathing (not wanting to lie down, but standing to make it easier to breathe).

    I would hope that you will see rapid improvement over the next couple of days. If you do not, please let your veterinarian know what is happening.

  190. Sonya F. says:

    Thanks for all of the helpful information on this blog. Can you advise on panting and shivering/shaking in my dog that received her 1st and 2nd shots last week? Today would be 8 days past the first shot. The past 3 nights she has gotten us up at all hours of the night with heavy panting and the urge to potty. During the day, she seems completely normal. The vet has her on 100mg of Minocycline (seems to cause her nausea @ 3 tablets by mouth 2x daily) Metoclopramide 10 mg 3x daily as needed for vomiting and Prednisone 20mg. My baby is a 62# Pit Mix about 6yoa in Stage 1 asymptomatic. Just want to see if the occasional panting and shivering is normal and what it could be a symptom of. Thank you in advance!

  191. Doc says:

    Hello, Sonya,

    Sorry about the late reply, but I was working at Scout Camp and no internet.

    I would not say that the panting and shivering is normal, nor expected.

    If it has not yet resolved, you might talk to your veterinarian about backing off one or another of the medications to see if it is a side effect.

    The prednisone is making her produce a more dilute urine, so she has to get up to potty more often, and drink more water to compensate for the loss.

    Some dogs do have mood alteration with the prednisone, though it is usually to the good. Sometimes it makes them wacky, though. If you haven’t yet discussed this with your veterinarian, please do.

  192. Mike says:

    I just wanted to leave a note thanking you for the wonderful advice you’ve given in your post and in the comments. I adopted a malamute who was heartworm positive and we just did the first melarsomine injection this morning. I’ve been stressing for weeks about how it was even possible to keep him confined to a crate for over two months (he HATES being in a crate) and maintain both of our sanities, but your advice regarding leash walks and aerobic exercise makes perfect sense. I live in Montana and the vets here have almost no experience treating heartworm, so my vet and I are learning as we go (the dog came from South Carolina).

  193. Leslie Nance says:

    I rescued a boxer a month ago and he is HW+. He is on the waiting list for the “fast kill” method that the Rescue will pay for. In the meantime my Vet has him on Sentinel monthly. He sleeps ALL THE TIME. He is so lazy and he is only 2. Do you think this is due to the heartworms?

  194. Doc says:

    Hello, Leslie,

    I am presuming that your doctor has already checked the dog for other medical problems.

    The only way to get an idea of how much heart damage is present is to take chest X-rays.

    If the dog just seems unwell, then doing some blood testing for other problems would be in order. I’d start with a complete blood count, blood chemistry exam, and a thyroid level.

  195. beth says:

    My 8 year old dog with Pemphigus tested positive for heartworms on January 21. His first injection is going to be March 21. I wondering if you know if him being auto immune compromised he would have problems getting this treatment?

  196. doc says:

    Hello, Beth,

    I’d really have to ask an internal medicine specialist to be sure about this one (if anybody can actually BE sure about this one).

    Typically, we give corticosteroids to control pemphigus diseases, at pretty high doses. We also give corticosteroids to dogs after heartworm treatment to minimize the inflammation that results when the dead worms shift position in the arteries.

    The problem here is that we don’t really understand auto-immune disease. We just don’t know why the body’s defense system gets wacky and decides to attack parts of the body.

    Any stressful event could make this flare up.

    The good thing is that the cortisone type drugs you would use for the pemphigus won’t interfere with the heartworm treatment.

    I would really suggest consulting with an internist if you are not confident about proceeding.

    I’m just not an authority on that subject.

  197. Jeri Harrell says:

    I am a foster parent to a 6 year old golden retriever who is 3 weeks out of her first shots for her heartworm treatment. She has shown few of the predicted side effects of the treatment until today. She was fine this morning. About 10:30 am she started shaking. She was soothed only by being right next to me. I have taken her out several times and she has not urinated at all nor is she drinking any water and did not eat her dinner. I tried to bribe her with chicken broth to no avail. She is sleeping at my feet as I type this. I will be taking her to the vet tomorrow morning but is there anything I need to be doing right now. Thanks so much in advance.

  198. Alicia says:

    Hello. My dog has heart warms and was having a bad cough. The vet suggested two options: one option is for the dog to take minocycline. The second option is to do an aggressive treatment were the dog will receive injections to breakdown the heartworms quicker. I’m currently using the minocycline pills on my rat terrier mix for two days, and her cough has decreased very quickly. I am not sure if I should do the aggressive treatment or stick with the minocycline pills. Please help.

  199. doc says:

    Hello, Alicia,

    If your dog is responding to the minocycline, this is very good. The drug is an antibiotic, but it also has anti-inflammatory properties, and this may be why the cough is improving.

    In addition, it inhibits a micro-organism called Wohlbachia. This micro-organism is in the heartworm itself, and is very beneficial to the heartworm. After 30 days of minocycline treatment, the worms will physically smaller, and they will be weaker and easier to kill.

    So, if your dog is doing okay on the minocycline, you would wait until after 30 days of treatment to do the “aggressive” treatment. By this, I suspect your veterinarian is speaking of the Immiticide injections that actually kill the worms.

    This must be done, as otherwise the worms are still there to cause your dog problems. Taking minocycline forever is not the answer.

  200. Ken S. says:

    I adopted my dog, Sadie, from a shelter 2 years ago. She was estimated to be 1 year old at the time. She is a mix of Chihuahua and Terrier. She weighs approx. 11 pounds and is 12 inches tall. She tested positive for heartworms but I elected to adopt her anyway. I had her treated with Immiticide. She was then put on Heartguard and am giving it to her monthly per my Vets instructions. After 2 years she is still testing positive for heartworms (adults) but has been negative for the babies for over a year. The vet has said that she has not seen this problem before. That is that the dog still tests positive for adult heartworms after two years. The vet has discussed two choices: 1) Second round of treatment of Immiticide, or 2) Continue giving the Heartguard monthly and hope that the adult worms present will die. The vet was not clear on what was the better alternative. I ask, “Wwhat would you do if it were your dog and the response was I guess I would treat it with the Immiticide,” but she wasn’t overly convincing. Overall, Sadie is in good health. She is not experiencing any symptoms consist with advanced heartworm disease. I am not certain I want to subject Sadie to this procedure unless is the better alternative. I have read your web pages on this topic and appreciate your thoroughness. I would be interested in your opinion in this matter. Thank you in advance for your consideration of this matter.

    Ken S.

  201. doc says:

    Hello, Ken,

    Generally speaking, the best person to advise you is the doctor who is seeing your dog.

    That being said, there are two scenarios that come to mind.

    First, we have to remember that the Heartgard (and other monthly preventives) work to kill the lifestage of the parasite that exists from mosquito bite up to about five to six weeks afterward.

    Second, it takes around six months from teh time of the mosquito bite for the adult worms to be developed in the heart. It is only at this stage that they can be detected with the blood test. This is also the stage when the Immiticide works.

    SO, there is roughly a four-month window where the parasites have matured past the point where the monthly preventive can kill them, but they haven’t reached the point where they can be detected with a blood test, or killed with Immiticide.

    If your dog was treated with Immiticide in October, for instance, and started on Heartgard at that time, baby heartworms acquired in June, July, August and September will go ahead and mature, and be showing up in the next spring’s blood test.

    The Immiticide may have killed all the adult worms present at time of treatment, but it didn’t keep the partially mature ones from growing up. Thus you have a positive blood test again, even though you were faithful with your preventive.

    The other scenario is the dog where the worms just don’t all die with the treatment. Some dogs (rare) will never get a totally clean blood test.

    My bias would generally be to re-treat with Immiticide in early spring. Any previous parasite exposure will then be in the life-cycle stage where they can be killed.

    In the case of a dog who had already undergone Immiticide treatment, and started on monthly preventive right away, we would expect very few worms to be present, and we would expect a good result from the treatment.

    I hope this is helpful to you.

  202. Ana Cecilia says:

    Doctor, I have 2 questions. I addopted a female dog aprox.6 years old from an endemic zone for dirofilarie. She already underwent immiticide treatment (3 doses) following the American Heartworm society guidelines. The last injection was on may 20th. 7 days after the injection she presented a cervical lymph node enlarged (adenopathy) not painful, easy to move, unilateral, about 2 cm diameter (her weight 12 kilos) My vet advice was waitful watching (but vets in my country dont have experience with melarsomine) Is this an adverse event? Should i do anything about it? My second question: we live in a zone not endemic now. Shall we keep her on dirofilarie prophylaxis for all her life? How long should we administer moxidectin after negative test? Thank you very much

  203. doc says:

    Hello, Ana Cecilia,

    I cannot imagine how the injection could have produced this enlarged lymph node.

    If this does not rapidly return to normal (I mean in a few days), it should be investigated. This could be a reaction to a foreign object nearby, an infection, or it could be a lymph node tumor. I think it highly unlikely that it is related to the heartworm treatment.

    As to whether you need to continue prophylaxis lifelong, I would consult veterinarians in your area. If you are in a desert or high mountain area without mosquitoes, then probably not. However, the preventives do have additional benefits, in that they help keep the pet free of intestinal worms, and some are combined with excellent flea control.

    Inasmuch as the dog has been treated before the mosquito season, theoretically you should be done. Personally, since the treatment can never be guaranteed 100% effective, I would follow up with preventive medicine for at least six months.

  204. Bill Brunett says:

    I have a 9 year old Labrador diagnosed with heartworms about 9 months ago. Prior to diagnosis, I kept him very active with long daily walks and swimming at least a couple of times a week – I noted before he was diagnosed he was coughing occasionally and had some periods of heavy breathing for no apparent reason, and that his lower rib cage seemed to get larger – could this expansion of the rib cage be due to the heartworms?
    I have been unable to treat him with immiticide because no vet in the area seems to be able to offer this treatment for less than $1500 and my financial circumstances do not permit such an expenditure, especially after paying a couple hundred bucks for exams and confirmation of the heartworm test.
    I am also concerned because in the event of thunder, he becomes uncontrollably afraid and has shakes for a long period of time, and thunder shirts are of no help. I honestly fear that in the event of immiticide treatment, he would be in extreme danger as soon as as the next storm.
    He has been given heartguard and 30 day treatments of doxycycline every 3 months for the past 9 months and I feel that this treatment has lessened his symptoms.
    I have taken him to 3 vets in the past 9 months, all of whom examine him(for a cost) then leave the room and have a vet tech return with a long list of charges for an immiticide treatment plan and I am told I can either perform this treatment plan or do nothing. If I ask about other options I am told there is nothing else, but when I bring up the doxycycline + ivermetcin treatment, they are aware of this treatment and willing to write me a prescription for doxycycline and heartguard after some argument, but they seem unwilling to discuss the treatment. I am beyond frustrated with vets that appear unwilling to work with me to form a treatment plan for my beloved dog that is affordable and I am desperate to know the best options I have in my situation.
    Is there any difference between doxycycline monohydrate and doxycycline hyclate? Which form would be more effective? Is there any other form of medicine I should be giving him other than doxycycline and ivermetcin considering that immiticide is not a possibility? I have limited his activity since the diagnosis but seeing him become lethargic makes me wonder if such restriction is the best choice in the long term. How much activity can I allow him without undue risk? Are there any other options for treatment? I have seen on some websites that immiticide treatment can be as low as $300, where could I possibly look to find treatment for such a cost?

  205. doc says:

    Hello, Bill,

    From Plumb’s Veterinary Drugs:

    “A semi-synthetic tetracycline that is derived from oxytetracycline, doxycycline is available as hyclate, calcium and monohydrate salts. The hyclate salt is used in the injectable dosage form and in oral tablets and capsules. It occurs as a yellow, crystalline powder that is soluble in water and slightly soluble in alcohol. After reconstitution with sterile water, the hyclate injection has a pH of 1.8–3.3. Doxycycline hyclate may also be known as doxycycline hydrochloride.

    The monohydrate salt is found in the oral powder for reconstitution. It occurs as a yellow, crystalline powder that is very slightly soluble in water and sparingly soluble in alcohol. The calcium salt is formed in situ during manufacturing. It is found in the commercially available oral syrup.”

    No difference in efficacy is mentioned.

    Doxycyline inhibits Wohlbachia organisms, which are beneficial to the heartworm, much as our gut bacteria help us. This weakens and physically shrinks the worms, but does not kill them. The drug also has some anti-inflammatory properties, which is helpful.

    The combination of doxy and ivermectin helps “hold the line” and prevent additional infestation. It will not kill the worms (not until a couple of years or more, anyway, if then).

    I cannot refer you to a cheap treatment center. We certainly charge much less than $1500, but for a big dog it would be more than $300.

    If he has heart and lung problems already (and it sounds like he does), then over-exertion is a no-no. He cannot compensate for the extra demand and may go into heart failure.

    Some dogs have more artery damage and will respond dramatically to treatment with anti-inflammatory doses of corticosteroids. This is temporary, but can really improve quality of life, and make the dog more able to tolerate the Immiticide treatment.

    Coughing and heavy breathing means that you waited until heart and lungs were damaged before seeking the diagnosis.

    If he can tolerate the Immiticide treatment (I mean the after-effects of the dying worms, not the drug), he may need support like any other heart-disease patient. This would mean diuretics, ACE-inhibitors, etc.

    There’s no quick fix. There may be only management until things are unmanageable any longer.

    Sorry I can’t give you an easy answer. The easy answer was regular heartworm preventive medicine before this happened, and that’s water under the bridge now.

  206. Don Allison says:

    Hi Dr,
    I found this site and find the information and discussion here very helpful.
    My dog is a rescue from the south. About 5 months after I got him he tested positive for HW. He is a 34 pound whippet/shepherd mix, very timid and nervous but otherwise has been healthy.
    He received the two immiticide treatments earlier this week. Your site was the first place I learned that the time period 4 to 5 days after the injections is when I should first look for signs the worms are dead. Should I expect him to cough? Feel poorly? sleep a lot? Low energy?
    So far he has done very well. He even ate food at the vet’s office a couple of hours after the injections each day.
    I am taking him out just to pee and poop, but he senses I am going to bring him back in after he does his business, so he is holding out on me, lingering a while before he goes.
    He is on pred and doxy also.
    Also the vet said his case was somewhere betwen stage 1 and 2.
    thanks for any advice.

  207. christine says:

    I have a four month old american pitbull terrier, he has heartworms, two days ago I gave him one tablet of D-worm combo broad spectrum de-wormer. He was acting fine the remainder of the day I gave him the tablet, the next evening he started having trouble breathing and began coughing, he has no appetite, and only wags his tale but is not his usual hyper and playful self. Is thisnormal?

  208. doc says:

    Hello, Don,

    If you restrict the dog’s activity for the next six weeks, you may never see any sign of illness. The most common things are just generally not feeling well, poor appetite, fever, coughing.

    If any of these things occur, or you just think the dog is “not right” in some way, let your veterinarian know as soon as possible.

    • Awie says:

      Hi doc!
      I appreciate all the work you have been doing here. I can’t seem to find out how to make a separate comment so I decided I will just reply here instead. My dog had his 7th heartworm treatment session earlier today, he then was walked by my cousin tonight who apparently let him speed up while walking aside from the separate instance of my dog accidentally running 2 feet because his leash was let go for a bit. He was panting after his walk. I can’t contact his vet right now because the clinic is closed by now. Should I be worried? Thank you so much!

      • Doc says:

        Hello, Awie,

        Just saw this. That short a time period of exertion is unlikely to make any difference in your dog’s recovery.
        That being said, if there is persistent distress, then you should contact your veterinarian.

  209. doc says:

    Hello, Christine,

    It takes heartworms six months to develop. If your dog is only four months old, he does not have heartworms. He should be taking heartworm preventive medication to keep him from getting heartworms when the mosquitoes bite him.

    It is not normal for dogs to feel bad after receiving a de-worming tablet. Coughing, trouble breathing, no appetite, and no playing all equal feeling pretty bad.

    This guy needs to see your veterinarian as soon as possible.

  210. Amy Weber says:

    We rescued a beautiful black lab who tested negative for heartworms 10/12. On 5/14, he tested positive although he has been on heartgard continually. He had one snap test and two lab tests done to confirm. Subsequently, our Vet put him on 30 days of doxycycline in anticipation of getting ready for the fast kill method of treatment. He had his heartgard medicine the day before we found out. After he was done the doxy, he had blood taken and checked under the microscope. As was expected, there was no larvae. Surprisingly, a snap test came up negative. Any idea what could be happening here? Thanks!

  211. Jennifer says:

    Hello. I first want to say this blog has been my sanity over the last 3 months that we have been doing HW treatment with my rescue, Bama. He is a Rottweiler and has become the absolute love of my life. I have 2 other rescued rotts and a wolf/husky mix that was rescued also. I found him online thru Facebook on Feb 28th and called the high kill shelter that he was being kept at while at work that Friday, they gave me less than 24 hours to come get him or they were going to put him down at noon on March 1st. I drove from Nashville TN to Texarkana AR in less than 12 hours to save him. I left Nashville at around 7:00pm Friday and got to Texarkana, AR at around 6:00am Saturday morning. He was emaciated (weighed 65# and I could see every rib and his spine as well as his hackles), had kennel cough, pneumonia, tracheal bronchitis and HW+ when I picked him up. I knew we were fighting an up hill battle when I agreed to take him. We had no background on him other than he had lost the majority of his weight since he was thrown in dog jail. When I got him back home, we went straight to my vet which is open 24hrs. We did xrays, blood work and he stayed over-night for observation, he started coughing in Memphis and didn’t stop. I will admit I was very scared because I knew he was very sick. We picked him up the next morning and he and I stayed in isolation for 16days till the upper respiratory stuff was cleared up, as I didnt want my healthy babies to get sick. He needed to gain a substantial amount of weight and muscle mass before we could even begin to address the HW issues. We fed, and still feed him a diet of baked boneless chicken thighs, eggs, and his kibble (Purina 1 Chicken and Rice), he finally gained enough weight that we along with our team of vets made the decision to start HW treatment. When I picked him up on Sunday March 2nd, he was immediately started on Doxy, Predinsone and a list of antibiotics along with IverHeart Max to pre-treat and kill the bacteria for the heartworms. His 1st round of Immeticide was April 27th. We opted for the 1 shot and 30 days late 2 shot regimen, (May 27 and 28th). We are now 3 weeks tomorrow from his last round of poison to kill the adult HW’s, we have continued giving him the IverHeart Max every month as well as he has been on Prednisone since. We have started the decrease down to stop it completely. Here in lies my question. He has had HORRIBLE gas since the day we brought him home. But in the last 24 hours he has started having diarrhea and is throwing up (2x’s since 7am, it was mostly undigested dog food and clear liquid, NO BLOOD). Everything I have read tells me this is NOT heartworm related as he has not had any breathing or coughing issues and I have called my vet, they do agree that this is not HW related. But I can’t help but be very scared. He seems to have lost his appetite, but I don’t feel like eating when I don’t feel good either. Our vet said that we could give him immodium and to call if anything changed. I guess I am just looking for reassurance that this is not indicative of HW complications. He now weighs 105# and out vet said that she had never seen a furbaby turn around as quickly as he has. I am sorry, i don’t mean to ramble, but it would absolutely break me. I cannot imagine going thru all of this and losing him. I WILL NOT LOSE HIM! I will do, sell or give up what ever I need to just to save him. (We sold my husband’s brand new mud tires off his jacked up jeep and one of our vehicles as well as opened a care credit account to pay for what we have done so far) I know you can’t give me specific advise or a dx but an educated opinion based on the above would be wonderful! Thanks — Jennifer

  212. Angela Lavallee says:

    Hi, I have just adopted a recue dog ( a four month process) who is heartworm positive, (stage 3). He received his last injection on May 20, 2014. We just brought him home June 12th. We keep him calm and crated at night only taking him out on a leash to use the bathroom. He is on 10mg of prednisone 2 times a day. The reason it took so long to adopt him was that his xrays showed some lung damage and heart enlargement from the heartworms and they were trying to make sure he was stable and that there wasn’t anything else going on. When we picked him up on Thursday they said that he may have to be on a low dose of prednisone for life. That my vet will taper down the dose accodingly and that he may never be able go running or play fetch. My question would be will he improve at all? I know he is still in the critical period of recovery from treatment right now, but over time will he ever be able to go for walks? Right now just taking him out to go to the bathroom he starts panting right away. Will any of the damage to the lungs heal over time? We will of course do whatever it takes to keep him healthy, I just hope for his sake he improves, because he doesn’t seem to understand right now why we keep him calm and more confined. He will be seeing my vet and I will be asking these questions also, just hoping there will be room for some improvement. I want to take him riding on the boat, swimming and at least for walks one day!! We Love him so much. He is a Blue Tick coonhound and is the sweetest ever!!! Thank you

  213. doc says:

    Hello, Amy,

    I would suppose that the dog has a very low worm burden. This can give false negative test results on the Snap test. If there are fewer than four adult female worms present, then the tests can miss them.

    When you give doxycycline, it weakens and shrinks the worms.

    I suspect the first tests were accurate, but you just have a very small number of worms present.

    The good thing about that is that your dog will probably not have much reaction to the treatment, as the severity of reaction is mostly related to the number of worms that must be dealt with.

  214. doc says:

    Hello, Jennifer,

    I agree that this very unlikely to be related to the heartworm treatment.

    That doesn’t’ mean it isn’t a significant problem. No appetite, vomiting and diarrhea sounds like something that needs to be evaluated, if it hasn’t resolved rapidly.

  215. doc says:

    Hello, Angela,
    I would definitely expect some improvement after recovery from the heartworm treatment.

    Removing the worms that obstruct the arteries gives the heart less work to do. Even though the heart is weakened (which we know from the enlargement seen), with less work to do, the dog may feel a lot better.

    However, it is unlikely that he will be an athlete. He may need additional medication to support his weak heart function, also.

    Your veterinarian is better equipped to answer your questions, as he/she is actually seeing the dog.

  216. Ana Cecilia says:

    Dear Dr. My dog is receiving monthly prophylaxys with advocate (moxidectin +imidacloprid) after her immiticide treatment. Now she resulted positive for erlichia. Her vet prescribed doxicicline. Can I add a prophylaxis for ticks as advocate does not cover them? Is there interaction with advocate? Which one do you recommend? Thank you very much.

  217. doc says:

    Hello, Ana,

    I appreciate your concerns. I feel sure that there is a tick control product that is compatible with what you are doing.

    You really need to discuss this with the doctor who is treating your dog. I cannot give you a recommendation under these circumstances.

    Best wishes.

  218. Deana says:

    We just had our bloodhound checked and he tested positive for heartworms. He has no symptoms at this point. He is an outdoor dog. We live in Hot Springs Arkansas, so our winter doesn’t really come until late October or November. The vet wants to wait until winter to treat him. Is this normal? It honestly scares me to death.

  219. doc says:

    Hello Deana,

    I am sure that your veterinarian is continuing your dog’s heartworm preventive medicine. This is important, so that you don’t acquire more worms.

    The theory behind waiting until winter is to kill any new worms that have developed in the six months since heavy mosquito exposure (this is how long it takes for the microscopic baby heartworm to grow to a size that the medicine will kill). That way you don’t have to go through the process now, and again in six months.

    If the dog has been taking preventive continuously but it just wasn’t 100% effective, you probably have a very small number of worms present.

    I wouldn’t let him overexert, do keep him on preventive, and share your concerns with your veterinarian. When a client doesn’t ask questions or call back with questions, we assume that we’ve done a great job explaining. Most doctors are very happy to answer your questions. We want you to understand why we make our recommendations. We are always trying to do what is best for you and your pet.

    Share your concerns with your veterinarian.

    Things will probably go well for you.

  220. kristy says:

    My newly adopted hound dog was given his last two shots of Immeticide 7 days ago. He’s 1.5 yrs old and has severe separation anxiety. We try to keep him calm but when either my husband or I leave he goes crazy. We can’t leave him alone either because he escapes out of his crate which causes too much excitement.I am worried that he is getting too excited because in the last 3 days he has coughed 7 times. Tonight before bed, he threw up a small amount of white phlegm. I checked for blood and there was none. Are these normal symptoms? He mostly sleeps all day. He has a healthy appetite and pink gums. Should I be worried? We’ve only had him for 36 days. Thanks!

  221. doc says:

    Hello, Kristy,

    A little cough occasionally, a little phlegm (no blood)wouldn’t worry me a lot.

    This next week is when you are most likely to see problems.

    If it gets worse, or he just starts feeling bad, or you see even a drop of blood, then he needs to be seen by the veterinarian.

    At 1.5 years of age, he shouldn’t have very many adult worms present, so the prognosis is generally good.

    Stay in close touch with your veterinarian and let him/her know your concerns.

  222. Katy says:

    Hi Dr. I adopted Sam, a two year old lab/golden mix from the humane society about 2 months ago. He was tested positive for heart worms and the humane society wanted to do a “slow kill” treatment. I took him to my wonderful vet who told me the slow kill treatment was no treatment at all and to do the regular injections to kill the worms. I took Sam in two days ago and brought him home today. Sam is usually VERY energetic and loves to cuddle! But right now he is barely walking around and sleeping a lot. Is listlessness a normal reaction? How long until he seems to be feeling better?

  223. doc says:

    Hello, Katy,

    I agree with your veterinarian on the so-called “slow kill” business. The American Heartworm Society agrees, as well.

    It is unlikely that the worms have died or shifted position (though not impossible).

    Some dogs have a lot of pain at the injection site for a couple of days. Let your veterinarian know that Sam is feeling bad. He/she may prescribe pain medication.

    If Sam is taking any form of cortisone for inflammation, it is important NOT to add pain medicine at random. There are medicines that are safe to combine with the cortisone, but there are some that are not.

    We do not recommend over-the-counter pain meds for dogs. Ibuprofen, aleve, and others can cause serious stomach bleeding in dogs.

    Talk to your veterinarian about this as soon as you can.

  224. Katy says:

    HI! I mentioned earlier than I brought Sam last week after his 3 day stay at the vets getting heartworm treatment. Sam has been doing a sporadic hacking. Like he’s trying to clear his throat.

    Is this normal or should I call the vet?


  225. Doc says:

    Hello, Katy,

    I don’t worry a lot about an occasional mild cough, as long as the dog is feeling good otherwise, eating well, no blood, and we are keeping the activity restricted.

    You should let your veterinarian know what is happening. He/she has actually seen your dog and will want to know what is going on, and can give you more specific advice.

    If you see any blood in his phlegm, coughing is more severe, or more frequent, any trouble breathing,he quits eating, or just generally doesn’t feel good, he should definitely see the doctor.

  226. Shannon says:


    My niece picked up a stray and I offered to cover the cost for him to get fully vetted if she would foster. She agreed. Long story short he is HW+ (with symptoms -coughing) And they neutered him. Now he is in ER with kidney and liver problems!! Any advice?

    Thank you in advance,

  227. Tori says:

    Hello, I hope you still reply here…

    My 7 year old Boston Terrier tested positive for heartworms a few months ago. The vet had her on a four-month treatment. Phase 1 was ivermectin once a week for four weeks. She did not do well during this at all, including a collapsing episode. Phase 2 was doxy and ivermectin, and she also began a twice daily treatment with furosemide. She did very well during this second month. Phase 3 was her first injection of immiticide. Things have gone HORRIBLE since then. She has collapsed three times (without being worked up), her breathing has been very labored. She is now on furosemide 3x a day for fluid build up, prednisone every other day, and albuterol to help open the lungs. She also just finished a round of amoxy to prevent pneumonia. The day after she stopped the albuterol, she began coughing/choking/gagging/hacking everytime she was up and about. The coughing has persisted for days. She was supposed to have a second and third injection of immiticide next week (she is now four weeks post-injection), but I am terrified to continue because of how adverse the reaction has been. My question is what do you think is causing the coughing at this point in time? Also, how bad will it be to end the treatment after only one injection? Thanks so much for your time.

  228. Doc says:

    Hello, Shannon,

    Kidney and liver problems would not be expected with either the heartworm disease or an uncomplicated neutering surgery.

    I would be concerned that the dog had been exposed to other diseases, especially Leptospirosis. I feel sure that his best bet is to continue with the ER doctors until stabilized. Then your regular veterinarian will have a better idea what diagnostic tests are needed.

  229. Doc says:

    Hello, Tori,

    Sometimes small dogs have much more trouble than large dogs, simply due to the fact that there is less space for the worms.

    I don’t see any reason why you could not continue the albuterol. Have you talked to your veterinarian about this?

    I don’t think that anyone would be ready to give more immiticide until the dog’s condition is more stable.

    We generally feel that the first injection kills about half the worms, the weaker half (young, old, and males). There are definitely dogs where the worst problem occurs after the first go-round (single injection). Most of their worms die at that time.

    It is entirely possible that the next immiticide treatment will not produce such a bad reaction.

    The good news is that waiting a few more weeks to give the immiticide should not reduce its efficacy.

    Discuss this with your veterinarian. I doubt that they will want to give more immiticide until the dog’s condition has stabilized. I am sure that they are as concerned as you are.

  230. Heather says:

    We rescued an english bulldog in February 2014 from a rescue knowing she was heartworm positive. She is showing no clinical signs (no coughing, tired, out of breath, no heart murmurs). The rescue had her on a month of doxy (then off 2 months) and then another month of doxy before we got her. She is also on Heartgard once a month. Our personal vet is very against the slow kill process and keeps pushing us to do the fast kill way. The rescue has had other bulldogs in the past that were positive and within a year, were negative with the doxy and heartgard way. Our bulldog has only been on the slow kill method since January 2014. Is there anything wrong with trying the doxy & heartgard for at least a year before reconsidering our options? We are a little thrown off by how different our vet explains it from the rescue and their preferred vet. I know its hard since you’re unable to see our dog but thought I’d get some additional advice.

  231. Doc says:

    Hello, Heather,

    The American Heartworm Society no longer recommends the “slow kill” method. There are two reasons for this. The first is that it probably won’t kill them. The second is that if it does kill them, you don’t know when it will happen. We want the dog’s exercise restricted during the period that the worms are dying. When will that be? Don’t know. How long will you keep the dog’s activity restricted? Forever?

    When you do the standard treatment, you can predict when the worms will die (and they WILL die), and care for the dog accordingly.

    The downside of continuing what you are doing would depend on how many worms are present. If there are enough to cause ongoing damage, then waiting a year is not such a not idea. If there are very few worms, then you’ll be okay. How do you know? You don’t.

    I’d be in favor of treating the dog with the three-injection protocol of Immiticide, on general principles, but I have not seen the dog, so my advice cannot be specific.

  232. Janet says:

    My foster dog has Babesia and was treated for it about 3 months ago. Now he is heartworm positive and will be treated with melarsomine. What are the implications and survival prognosis? Thanks in advance.

  233. Doc says:

    Hello, Janet,

    I do not have experience with Babesia in my practice area. In my reading, I do find that there are sometimes relapses under stress.

    Some dogs remain asymptomatic carriers. Some are permanently cured.

    If the dog is doing well otherwise, I would expect him to have no more trouble than another dog with the treatment.

    Again, my experience with this particular situation is nil.

    Your best information will come from your regular veterinarian who is seeing your dog.

  234. JJ says:

    First, thank-you for your willingness to answer all these questions. The peace of mind you provide is immeasurable.

    Our 45 lb lab mix rescue has undergone hw treatment, basically under the same protocol you recommend. She had her 2nd & 3rd Immiticide injections 10 days ago and it seems she has responded as well as can be expected. My question regarding steroid meds; the vet did not prescribe any steroid meds after her Immiticide injections. On about day 6 after her injections she coughed up clear mucus about 8 times. It has lessened since then. She coughs once every few hours now and does not produce mucus, but it still sounds as though she’s trying to cough something up. I’m just wondering if we should call the vet and ask for (possibly insist on?) steroids with these symptoms? She was moving slowly the day she coughed up mucus but now seems to be much more energetic. We called twice explaining the coughing/producing mucus to the tech on the phone and they said these were normal reactions. We weren’t given the option of talking with the vet or even that they’d give her a message. Should we call again and push more on the issue? She is improving, but I’m just not confident that she shouldn’t be on steroid meds — it sounds as though you prescribe them as a standard part of treatment.

    Thanks so much for all you do

  235. Doc says:

    Hello, J.J.,

    The corticosteroids are a potent medication, and do have side-effects. Many veterinarians do not like to prescribe them unless they are certain that the drugs are needed.

    I send them home routinely with dogs after heartworm treatment because I feel the side-effects are manageable, and it has greatly reduced the number of dogs in crisis after heartworm treatment (95% fewer).

    If she is improving, she may do fine without them. It would be important to keep her very quiet, and to again contact your veterinarian with a progress report.

  236. Donna says:

    Hi Doc! I just wanted to thank you for providing this wonderful informative blog–I’ve learned a lot from it!

    We adopted an Aussie mix, Jack, from the SPCA in August. He had tested HW- in April when they got him and they started his HW preventative meds, but when I had him re-tested this month he was HW+. We started him on a month of Doxycycline last week and he will have his first injection in November, followed by two injections in December. We have a great vet who is good at answering all of our questions. I have had lots of dogs, but never one with heartworms and I’m so sad for Jack having to go through this. I started looking online for a support group, because it’s good to hear from regular people who are going through the same thing. Now I don’t feel so alone (a.k.a. “misery loves company”).

    Anyway, my concern right now is that our vet has advised us to restrict Jack’s exercise NOW. He is normally a pretty chill guy for his age (between 1 and 2 years old). But we have this demonic bulldog puppy who instigates all kinds of mayhem. As calm as Jack is, he does love to play with her. Do you have any suggestions for the situation I’m in, or will I just have to muddle through the next 4 months trying to keep them separated? They are both inside dogs. I have bought a big wire crate for Jack but I hate to use it until it’s really necessary because he doesn’t like being crated.

    Well, thanks again for taking the time to answer all of our questions–you’re doing a good thing and a much needed thing!

  237. Doc says:

    Hello, Donna,

    Jack is not at any more risk taking the doxycylcine than he was before he started taking it.

    The worms present could actually move at any time, even before you do any treatment. We rarely see a problem with dogs that have just a few worms, but I have seen dogs that came in coughing up blood. These were dogs that had not undergone treatment, they just had a bad situation with the worms in their pulmonary arteries.

    Ideally we try to minimize “contact sports” and heavy aerobic exercise for these patients. My personal feeling is that this is most important in the weeks following the Immiticide injections. Of course, I haven’t seen Jack and your veterinarian has.

    It would be best to supervise the two dogs when they play together so that you can slow things down.

    I usually feel like it’s okay to go for walks on the leash, wander around the house or in the yard, provided you don’t have a lot of exciting activities (which the other dog would qualify as).

    If you think “no aerobic exercise”, then you should be on the right track.

  238. Sarah Beth says:

    This is all great down to earth infof so I am hoping you can clarify a couple of concerns I have. For background: We adopted a heartworm positive 19 month old mutt, Sargeant, on Nov. 18. The shelter did the test and gave ivermectin on Nov. 12. We took him to a vet who was new to us on Nov. 20 and started him on one month of doxy. Along with doxy we gave regular dose of ivermectin on 11/29 and 12/24. We weren’the comfortable with that vet’s office – very crowded, billing mistakes, etc – so we switched to a single doc practice. So far everything we are doing aligns with best practices I’ve read about. Sargeant went for his first shot on Monday 12/29. We did’nt realize it until we got there but the vet opted for the 2 shots in 24 hours treatment. Despite having read that the heartworm society recommends the 3 dose option and it is more effective, we trusted her judgement to just do 2. She said she was a rural vet for a long time, had treated hundreds of dogs with heartworms and always used 2 doses only.

    He had more than expected pain and swelling from the injection so he stayed 2 nights.

    I asked when we picked him up about the possibility of juveniles surviving. She said not to worry about it because ivermectin and immiticide would kill all of them at all stages. This is not in line with what the heartworm societymology info says.

    I’m also concerned that she gave us ammoxicillin vs. Doxy to prevent infection. I don’t see ammoxicillin listed anywhere as part of heartworm treatment.

    Sargeant is home now and doing great, but I am nervous that we might not be getting top notch care. Any thoughts or insights on the juvenile worm issue and logic behind ammoxicillin? Note all blood tests are normal, he’s asymptomatic, and heart and lungs sound normal. Thank you!

  239. Doc says:

    Hello, Sara Beth,

    The doxycycline is not to prevent infection. It is given to weaken and shrink the worms prior to treatment to kill them (the Immiticide). It does this by attacking the Wohlbachia organisms that are beneficial to the heartworm.

    The doxycycline is given for several weeks before the Immiticide injections, and its effect lasts for months.

    I understand about the 2 versus 3 question. When Immiticide was first introduced, 2 injections was the standard treatment, and most dogs did show a clear blood test with this.

    The 3-injection protocol was first introduced for safety’s sake – kill part of the worms with one injection, then kill the rest with the two injections a month later.

    A single injection kills only the weakest worms. These would also die with two injections.

    Research has shown that some dogs will clear 100% with two injections, and some won’t clear 100% even with three injections. Sometimes a few survive no matter what you do (this has been documented with autopsies on treated dogs).

    A higher percentage get 100% kill with 3 injections than with 2 injections. Is it a significantly higher percentage? Hard to say.

    I do the 3-injection protocol for safety’s sake, so that all the dead worms don’t hit the dog at the same time.

    Dogs who have been infected by the mosquitoes in July and August will have worms that won’t be fully developed, detectable or treatable until six to seven months later, i.e. January and February. At two months post infection, the preventive (ivermectin) no longer affects them. The Immiticide doesn’t kill them until they are adults, six months or so after infection.

    This is why some dogs get a thorough treatment protocol, but show up with a few worms later, despite taking preventive medication.

    I cannot speak to the amoxicillin. You should ask your veterinarian about that if you have concerns. We usually treat the dog with prednisone to minimize the inflammation after the worms die, but not everyone does that on a preemptive basis, as we do.

  240. Lisa says:

    My dog is undergoing HW treatment. She had her first injection on Jan. 9, is doing quite well, and goes in for the next 2 injections on Feb. 2. Her whole case has been confusing, because she has been on preventative, and has tested negative up until Oct. 2014. When trying to get Novartis to cover the cost, they claim she could have gotten infected in April or May of 2013 (she did not start the preventative until May 2013). However, the test came back weak positive, and negative from the in house test at the vet. A second round of ELISA was done at IVexx, that again came back weak positive. Here is my understating. A weak positive means a recent infection. But that doesn’t seem to correlate to the May 2013 exposure, does it? Seems to me that 18 months would not be a recent infection. Please let me know what you think. Also, she is having TERRIBLE and constant gas. Is that normal during treatment? Or a reaction to prednisone? Thanks …I love this blog.

  241. Jason says:

    Hello Doc,

    I rescued a dog in November of 2013. We had him tested for heartworm but received a false negative due to the lack of antigen at the time. I did not know the life cycle of heartworms so he was not tested again until November 2014 at which time he tested antigen positive. We followed that up with a Knotts test for Microfilaria which was negative due to the fact he had been treated with Ivermectin monthly for one full year.

    We administered Doxycycline for 30 days and then he received his first shot of Immiticide on 01/12/2015 and two days of Metacam. Despite strict exercise restriction, at 2am Saturday morning(01/17/2015) he developed severe vomiting and diarrhea(bloody). We nursed him through the night as he was was still continuing to drink water and met our vet at the door upon opening Saturday morning. She placed him on an IV and antibiotics and he responded but not well enough to come home. So, that evening we transferred him to a 24 hour care center which he stayed two nights until Monday morning; at that time we transferred him back to our vet for another full day of IV treatment. Thankfully he is doing very well now but I am very concerned about how and when to finish his treatment. He is a dog with a very sensitive GI track to start with. We are unable to pinpoint the cause of his severe reaction, meaning was it the Immiticide or a mass worm die off? Having been on Ivermectin for as long as he was is there a chance that between the Doxy and and first shot of Immiticide (which my vet stated was on the high side) we had a full kill off and should wait, test, and then possibly treat again at a later date? Should I possibly consider just continuing the monthly Ivermectin from this point with a monthly dose of Doxy every other month? My vet is fantastic, we just don’t get the volume of cases here in Illinois to know how to deal with outlier situations.

    Thank you so much for any information you can provide,

  242. Doc says:

    Hello, Lisa,

    Typically, the companies that make the preventive medicine require a negative test when you start (unless the dog is less than four months old), and a negative test six months later. It takes the heartworms six months to develop to a stage where they can be detected by testing. If both these tests are negative, then the dog didn’t have heartworms before starting the medicine.

    The antigen tests for adult heartworm protein test for a protein from the female heartworm’s reproductive tract. If there are fewer than four female worms present, you can (but don’t always) get a false negative test.

    A “weak positive” means there isn’t much of this protein in the bloodstream. It has to do with numbers of worms present, not the duration of the infection. It means there aren’t very many worms present. A small number of worms could have been present for a long time, and have been missed on earlier tests.

    Terrible gas is not generally related to either the heartworm treatment or prednisone.

    Here’s one link to look at:

  243. Doc says:

    Hello, Jason,
    It is difficult to say what caused the problem your dog experienced. I have never seen this type of reaction with Immiticide (out of hundreds of dogs treated). Most dogs tolerate Metacam well, but that whole class of drugs (NSAIDs) have the potential to cause stomach problems.

    I usually treat with some type of corticosteroid (cortisone) for the inflammation, rather than an NSAID. Some dogs can be very sensitive to that, as well, though. If I were going to use that next time, I would include a stomach protecting drug like Sucralfate, since your dog obviously has some unusual issues in this department.

    For pain, we add Tramadol, if needed. Some dogs have a lot of pain at the injection site, and some don’t appear to have any pain at all. I am not able to predict which dogs will hurt.

    In rare severe pain cases, we sometimes use a combination of acetaminophen plus codeine (Tylenol #3 or #4). Codeine can cause constipation.

  244. Michelle says:

    I recently rescued a stray who tested heartworm positive. She has begun treatment – antibiotics and just received her two shots 24 hours apart. I continue to read and educate myself because the more I know, the better I feel. This is how I came upon your site. I just wanted to say thank you for putting together such concise, easy to read information. Basically, great job and thank you!

  245. Doc says:

    Hello, Michelle,

    Thanks for your kind words.

    Well done on rescuing this dog and taking the responsibility to bring her back to full health.

  246. Sheila says:

    My 9 year old 13 lb shitsu mix tested positive for heartworm at his yearly exam. He had no symptoms and I was surprised. The vet said it was probably stage 1, no probs with heart and lungs upon X-rays. He did fine after the first shot, a little whimpery. I gave him a dose of rimadyl. About three weeks later he was in the house and began shaking. I thought it was because a lawn mower was near the house. In the past, on occasion he would shake for a minute or two if really excited or a loud bang or crack of thunder. These shaking episodes continued and the following week before injections 2 and 3, the vet checked him out. Said he dos not know what the shaking was and continued with the shots. Che did fine from the shots. It is now almost 3 weeks later. The shaking comes and goes almost daily. When it occurs his tail is down and he will often stay go into the mudroom away on his own. He does not do this in bed at night. It does not appear to be like a seizure, it is more like trembling. It occurs more frequently and for longer periods. He appears mor aloof and not as happy. He continues to eat and drink but even the begging is not there during an “episode”. Could this be from the treatment? No coughing or panting

  247. Doc says:

    Hello, Sheila,

    This doesn’t sound like complications from your heartworm treatment.

    It makes me think of a seizure disorder, with very mild seizures.

    Try to get some videos for your veterinarian to look at.

  248. Kyela says:

    My 10 yr old dalmatian mix tested positive for HW. Our vet put her on 2 weeks of doxy, 300mg/twice a day. We are now on the 2nd week. We are scheduled to visit the vet again on Sunday for a few more blood tests (at least that’s what’s on her check-up form). No schedule for an xray –is that normal? I’ve been reading this blog a lot and it has helped me understand the whole treatment process and the what to expect post-treatment. I was wondering though if it’s safe to do the fast kill method for my old dog. She has never had any serious health issues in the past but I’m not sure if her heart can still take the stress for when the worms starts dying off. She is panting a lot lately and would cough a few times a day. I asked the vet if there was an alternative to the fast kill (since she said it was like chemo) and she said the other option would be to administer Revolution. I’ve read about it and it doesn’t seem to be effective. I’m just scared and feel like we’re not getting the best treatment. We were also not prescribed heartguard because the vet says my dog already tested positive for HW. I’ve read a lot of comments here who had vets prescribe heartguard even if their dogs tested positive as a kind of protection. I’m so confused and scared for my dog. Help!

  249. Doc says:

    Hello, Kyela,

    Not having seen your dog, I can’t really second-guess your doctor.

    I’m not sure what blood tests are being run or why, so you should ask your doctor about that.

    Chest X-rays are not always a routine part of the work-up.
    Chest X-rays will give you an idea of how much of the problem is directly heart-related versus lung-artery-related. If you have more lung artery disease, then some dogs will benefit significantly from being treated with anti-inflammatory doses of prednisone.

    Revolution is approved to give to dogs that have heartworms. It is unlikely to cause any problems. It should keep them from getting any more worms than they already have. It is not going to do anything to kill the adult worms present.

    Heartgard is not officially labeled for use in dogs who already have heartworms. However, the American Heartworm Society recommends Heartgard for dogs who have heartworms and are undergoing treatment. Again, it would take years for Heartgard to kill adult worms (if it ever did), but it will keep you from getting more worms than you already have.

    The problem with Immiticide is not toxicity of the drug (as it would be with cancer chemotherapy). ANYTHING that kills heartworms, will result in dead worms floating downstream into the smaller lung arteries. It is this situation that causes the complications.

    If you are not comfortable with what your doctor has recommended, ask her to explain things to you in more detail. If you are still not comfortable, then seek a second opinion from someone who can actually see your dog.

  250. Tressia tousignant says:

    I have two American Bulldogs that are both going through heart worm treatment now . One started the first week of February due to noticeable cough, weight loss and lethargy. This dog was almost lost last year due to snake bit to her head, took incredible measures by emergency vet to save her, so is doing well but unfortunately with the amount of damage to heart and lungs by the two issues so close together has made her slow down a lot. The sister didn’t have any symptoms when tested later in March but was also positive, so started the treatment as well, due to an issue with getting the drug she just had her second major shot three to four days ago (unsure which day due to requirement to stay overnight till late afternoon next day) today she has been throwing up a lot, twenty minutes ago she got sick again, while I was trying to soak up fluid from bedding I started looking at how dark it was and realized it looked liked old blood and found a few black clots as well as what appeared to be a few bright red spots, I’m unsure whether to go to emergency vet as its Saturday and normal vet is closed now, is this a common occurrence is she in major danger? Both are as I said sisters and are a few months from being four years old. Help??

  251. Doc says:

    Hello, Tressia,

    Bringing up blood is never normal. I consider it something that needs attention as soon as possible.

    Heartworm treatment doesn’t usually cause vomiting, with or without blood. They are more likely to cough up phlegm, with or without blood (and, rarely, a lot of blood).

    If due to coughing up blood from lung damage, treatment is usually very close confinement to keep the dog from exerting itself and raising blood pressure. We also put them on anti-inflammatory doses of prednisone (a synthetic form of cortisone).

    If I had a patient vomiting repeatedly and bringing up blood, I’d seek medical attention as soon as I could.

  252. Julia Burzon says:

    Is this still active? Bc if so I have a question: I a trainer and have been contacted by a rescue with a dog that has been treated for heart worms and allowed to do whatever he wants, behaviorally, for an entire summer in order not to “stress” him. I understand restricting movement to keep heart rate down, but but to what extent and should it be allowe to to affect handling? Thanks

  253. Doc says:

    Hello, Julia,
    I don’t think that allowing the dog to be an outlaw is part of the recuperation for heartworm treatment.

    What we want to do is avoid aerobic exercise for six weeks after the last of the Immiticide injections. Walking on a leash (not fighting it vigorously) is okay. No running loose. Avoid hard charges across the yard to attack the mailman.

    Once he has completed six weeks after the last of 3 Immiticide injections, he should be gradually returned to normal activity. Of course, if it’s 100 degrees, you wouldn’t work any dog hard in those temps.

  254. Tim says:


    We adopted a female catahoula mix, 3 weeks ago August 18th, from a shelter, and as required, she was spade and given all shots including pro heart 26-50lb, she weighed 37lbs, and tested low positive antigen. She was also given Sx meloxicam injection, along with rabies vaccination. Then delivered to us the next day. Needless to say she was very sick and no appetite for a couple of days, and dropped to 34 lbs, we tried all types of food to get her to eat, and she had diaherea. But she finally started eating with much encouragement. We took her to a vet for consultation on HW treatment and she suggested 3 shots after 30 Days of doxylin. But wanted to wait until Pepper gained weight. We have since picked up a stray beagle, and they have become very active together, and she now rushes to eat and has steadily gained weight, now 41 lbs and looks very healthy and energetic. we will go through the full treatment, but after researching have questions on the timing of treatment, we want to treat as soon as possible. Do we need to wait the full 30 days of antibiotics, and should we treat now since we do not know when she was infected as she was in the shelter for 2 months. Our vet test showed high positive vs the low from the vet that the shelter took to have spayed. If we treat her now after only 3 weeks of heart worm shot, what are our chances of not killing all adult and future heartworms? Thanks for your time and dedication to this. Tim, Karin, and Pepper.

  255. Doc says:

    Hello, Tim,

    I wouldn’t put too much weight on the strong or weak positive business. That test is pretty much yes or no.

    The moxidectin (ProHeart6) injection has killed the baby heartworms that were injected by the mosquito in the five weeks previous to giving it, and will continue to kill any that the mosquito puts in for the next five months.

    This means that it does not cover the mosquito exposure the dog received in May, June, and early July. These heartworm larvae won’t mature to the point where they can be treated for six months after they entered the body. Thus, even if you clear the dog with treatment now, it could show up positive next Spring.

    They will NOT add to the heartworm burden that the dog presently has, as far as treating the dog in the next 3 months.

    The doxycycline will weaken and shrink the worms. You take it for four weeks (or 30 days). Now the American Heartworm Society recommends a four-week wait after that. Then you do the first of the Immiticide injections.

    So, yes, you should do the full 30 days of doxycycline. Follow your veterinarian’s guidance. Ask questions of the doctor who is actually seeing your dog. I can only give generaly information.

  256. Sehee Kim says:

    Hello doc,

    I’m Sehee from Korea (South, of course). Im posting it from far away from where you are because you seem so many experiences in treating HW.

    Last Tuesday and Wednesday my dog, Pekomi got the injections, 24 hours apart. It’s been about 5 days now, and as i read your comments, i found now is the most dangerous time for my dog as worms start to die and they shift their position at pulmonary artery.

    But i didn’t crate him but let him move and roam the house as it is not very large, and what’s worse is that i have to let him go out to pee and poo. He has been raised outdoor so he doesn’t allow himself to do that indoor. But i’m worried because he’s very energetic and athletic dog, so it is just a few minutes but he runs jump and walk fast. He seems to feel bad now but luckily doesn’t show any distress signs such as coughing with blood, phlems. He eats well and he has a strong apetitie.

    So my question is do you think heart rate rise for a few minutes could cause severe complications to him?

  257. Doc says:

    Hello, Sehee,

    We just have to do the best we can with these situations. It is not desirable for the dog to stay in a cage for six weeks. We just keep him as quiet as we can. As long as he’s not out running loose, your risk from exercise is pretty small. Okay to walk on a leash, playing loose in the house. Supervise him outside and do what works to cause the least exertion.

  258. Linda says:

    My two dogs were just treated for heartworms. They received their injections on 9/15 and 9/16. My male was very sore for a few days but is improving. My female has acted fine until earlier today when she coughed and vomited (no signs of blood) while we had her outside to potty. We are keeping them quiet and take them out to potty on a leash. My male walks quietly on the leash but my female is a puller and it is very hard to hold her back. I’m worried that this is going to cause problems. Do you have any suggestions on how we can get her to walk quietly? I checked on her about a half hour ago and she was coughing and gagging again and she was panting, so I’m sure its stressing her out. Is the coughing and gagging normal? With it being Saturday night, our Vet won’t be in again until Monday. If she is still gagging and coughing I plan on calling our vet on Monday. I just checked on her again and she is sitting on her pet bed and she’s no longer panting (or gagging and coughing). We are giving each dog one aspirin a day as instructed by our Vet. Thank you in advance for any advice.

  259. Dana says:

    We just rescued a 2 yr old Bloodhound. On her first vet visit, her heartworm test was a slight blue and suggested we retest her in a month. A month later, and a different vet, she tested positive for heartworms. Vet put her on a month of doxycycline hyclate and heartgard. Vet said this was to kill the baby heartworms and to retest her in 2 months and if positive, to start heartworm treatment. I haven’t seen any other posts like this. Is this normal protocal? I just feel like those worms are growing inside her and need to be addressed now.

  260. Doc says:

    Hello, Linda,
    If your dog continues to have problems, you could talk to your veterinarian about possibly using a mild sedative at difficult times. If she is having complications with the dead worms (which could be happening, even though it’s a bit earlier than we usually see that), he/she may put the dog on some form of oral corticosteroid (a cortisone type drug, like prednisone, for instance) rather than the aspirin.

    Keep your veterinarian posted as soon as you can.

  261. Doc says:

    Hello, Dana,
    The doxycycline and Heartgard are the first steps in treating the dog. They may kill the baby heartworms in the blood. The big reason for the doxycycline is to weaken and shrink the adult worms, making them easier to kill and dissolve out of circulation. The drug inhibits a micro-organism called Wohlbachia that is beneficial to the heartworm. Without it, they get weaker and smaller. The effect lasts for several months.

    The Heartgard is killing any new baby heartworms that the mosquito is injecting now.

    The typical time to begin the Immiticide injections that actually kill the adult worms is after one month of doxycycline and one month’s rest, just what your doctor is suggesting.

  262. Brent Johnson says:

    Hi my German shepherd mix received her last treatment 2 weeks ago. I have not kept her strictly in a crate but i have limited her as much as i can. However as of tonight shes been panting heavily for hours and doesnt seem to be calming down. If she is experiencing excitement from her anxieties when im not home could that be what is causing this heavy panting? Also is it something that i need to worry about? I cant get a straight answer from anyone. Inmight be over thinking it but shes my best friend and dont want to take any chances. Thank you so much for your time

  263. Doc says:

    Hello, Brent,
    Sorry I’m behind on these answers. I hope your dog has improved.

    Since this behavior was different from previous normal behaviors, it certainly could be related to the movement of the dying heartworms.

    Any time that a dog is exhibiting unusual behavior in the weeks after being treated for heartworms, I would wish to re-examine the dog.

  264. Linda says:

    Thank you for your response. Both of my dogs seem to be doing quite well now. They are now entering week 4 post treatment. I’m still taking them out to potty on leash. Our regular vet said to keep them quiet for a month (30 days will be this Friday), but she is out right now and a new vet covering for her suggested that we continue to watch them for an additional week. She said let them out off leash but don’t let them over exert themselves. I was wonderjng if she was just being cautious because she is young and new or could it be because the dead worms won’t be dissolved yet? How long does that usually take? I hate to keep bothering her because I know she’s swamped since she’s covering for our vet too. I’m nervous about letting them out in the yard next week but I fill in part- time and i had told them i couldnt fill in for a month and next week I am scheduled to work Wed, Thurs, and Fri. Do you think they will be okay? By then it will be 5 weeks since their last injection. They had a stage I case, all major organs were okay. Thank you in advance for your time.

  265. Doc says:

    Hello, Linda,
    I have seen figures of 5&1/2 to six weeks until all the worms are dissolved. I think it is highly unlikely that you will have any problems at 5 weeks.

  266. Doris says:

    Hi Doc,
    We have a rescue (5 year old) who has tested HW + but has other health issues, one of which is stage 3 kidney disease with a PLN of 21. His vet prescribed the following: 100mg of Doxy (2 pills, twice a day, 400mg total daily), 500 mg of Cephalexin (1 pill, twice a day), and 10mg of Benazepril (one pill daily). He is also on a special diet for the kidney issue. My question is concerning the Doxy and his kidney issue is it a dangerous combination? Would you recommend a different treatment. Thank you, Doris

  267. Doc says:

    Hello, Doris,
    This is a difficult situation, with more than one disease process in play.

    Doxycycline is often used to treat a very bad kidney infection called Leptospirosis, and is not generally considered to be something that would make his kidneys worse in any way.

    I cannot really give you specific advice as to treatment recommendations. It sounds like what your doctor is doing is appropriate, given the information I have.

    Your doctor will probably be monitoring your dog’s kidney function in response to these medicines. The benazapril helps stop the protein leakage, which is important, as the leaking protein causes even more kidney damage. However, it can also have a bad effect on the kidney itself in some dogs, so I suspect your doctor will be checking kidney function tests periodically.

  268. taylor says:

    I recently adopted a dog from the shelter who had two injects (I believe) in the lower lumbar and a lot supplied us with med to give him once a mth. We have had him for two weeks now. My boyfriend not aware of the seriousness of heartworms took him on a pretty far walk since then for 2 days now I have noticed him begin to cough a lot more and breath heavily, I know coughing is normally after beginning treated, but should I take him to the vet since it started after that walk (he knows better now to not take those long trips with the dog)

  269. Doc says:

    Hello, Taylor,

    If the dog is continuing to cough, I would definitely get a checkup with your veterinarian.

    Short walks on leash should be okay, but you really don’t want the dog exerting itself.

  270. JRV says:

    I am having some concerns based on what I read online. My dog was not given antibiotics or steroids. Correction, we were not given any to administer at home, with her heartworm treatment. She did receive steroids in the office while they kept her overnight and did the 2 injections 24 hours apart I have asked my vet about this and he was dismissive (which I can get to an extent, I’m sure it is very professionals dream to have people come in quoting the internet). She has also received Denosyl. I am just worried to be sure everything is being done to support a successful outcome for her. Do you think antibiotics prior and steriods after are considered the standard in treatment? Or is it common in your experience that there are many different protocols all used successfully? The vet did indicate based on her test numbers that she was not highly infected. However no ultrasounds or further testing were done to stage it or such.

  271. Doc says:

    Hello, JRV,

    For many years, nobody gave the doxycycline or minocycline. The data on Wohlbachia wasn’t known. Most dogs were treated successfully. The benefit of the antibiotic is that the worms get smaller, weaker, easier to kill, less of them to cause a blockage. Apparently you don’t have many in the first place.

    The downside of the antibiotic pre-treatment is adding two months to the treatment protocol, and a significant expense with larger dogs (like another $100). Also, the drugs make some dogs queasy.

    I don’t think that ultrasound would have given you much helpful information unless the dog were having problems with poor heart function. It’s not really any help in counting the worms, or predicting how the dog’s body will react to the death and movement of the worms.

    For many years, I did not administer steroids unless the dog began having problems. Many dogs with few worms showed no outward sign of complications, so did not receive them. However, since I have been giving them routinely after the treatment, complications requiring additional treatment have been virtually eliminated. Before, I would have to treat about one third of the dogs for complications a week or two after the treatment to kill the worms.

    While the American Heartworm Society does publish what they recommend as a standard protocol, every patient is different, and the doctor seeing your dog is usually the person best equipped to advise you about him.

  272. ann fuller says:

    This is a great website. I have a young pit mix from Texas who was HW positive. I live in AZ and had him treated with the 2 injection protocol. That was 10 weeks ago. He was microfilaria free 6 weeks ago. My vet just said no hard exercise, adult worms are still dying off. Is that possible?

  273. Doc says:

    Hello, Ann,

    Generally speaking, I would think things would be pretty well cleared out by 10 weeks after the two Immiticide injections. However, I have not seen your dog. I think it best to rely on your veterinarian’s recommendations.

  274. Kim says:

    Our dog had treatments on December 17 and 18 2015. She’s been doing moderate activities for a few weeks and we just can’t keep her calm anymore. Is it safe to let her out to run? She’s obsessed with running and hiking. We just don’t want to start too early.

  275. Doc says:

    Hello, Kim,

    The doctor who is seeing your dog is always your best source of advice. I can only give general information.

    Generally speaking, by six weeks post-treatment, the adult worms have died and been dissolved, so the risk is minimal.

    There are rare cases where a pulmonary artery has been weakened during the time it was blocked with dead worms. When the dog begins to exercise vigorously, the increased blood pressure causes a blow-out, and the dog coughs up blood.

    This is pretty rare. I have treated hundreds of dogs for heartworms over the last 38 years and have seen this happen twice.

    Again, you really should consult with your regular veterinarian on this.

  276. Linda R. says:

    Hello. Both of my dogs went through heartworm treatment last Fall. My female is now heartworm free but microfilaria kept showing up in my male dog even after a few extra doses of oral Immiticide (I believe this was what he as given). Our Vet said the only reason this could keep happening was that the first treatment didn’t kill all of the adult heartworms, so he is going through another treatment. This time our Vet is doing it in two stages. First our dog was given a treatment and we brought him back home the same day (I don’t know what med was used). We have to keep him quiet for 30 days, then bring him back for the 2-injection treatment (like he had last time). Is it common for heartworm treatment not to kill all the adults and why would this happen? Also, what happens if this treatment doesn’t work? What would the next step be? I didn’t get a chance to talk to our Vet when I picked our dog up. Usually she talks to us but she was busy with another dog that was brought in. Thank you in advance for your time.

  277. Doc says:

    Hello, Linda,

    It sounds like the oral medication was probably ivermectin, as this is often used to kill microfilariae.

    Immiticide is the injection used to kill the adult worms. It is certainly possible to go through the treatment without killing 100% of the worms. There are some dogs that will never be 100% cleared (very few thankfully). After you go through the 3 dose regimen, 1 now and two later (the highest chance of successful clearing out), if the dog is still not clear, the worm burden would be so small as to be negligible in relation to the dog’s health. Be sure to stay on your preventive medicine.

  278. Linda R. says:

    Thank you for your fast response. Now that you mention Ivermectin, I do remember that was the oral dose he received. Both dogs have been on Trifexis since last Fall and I will definitely make sure they stay on preventive medicine. There is no way that I want my dogs to go through the treatment again. Our Vet did mention a shot that could be given every six months. Do you know anything about that?

  279. Doc says:

    Hello, Linda,

    The six-month shot that I am familiar with is Proheart-6. This is a slow release moxidectin. If you can remember to get it on time every six months, you wouldn’t have to remember giving a pill every month. It doesn’t really help to control intestinal worms or fleas. It’s mostly just a heartworm preventive, though a good one.

  280. Linda R. says:

    I’m sorry that I keep posting but I was reading a post about how quiet to keep a dog after heartworm treatment. My dog is an outside dog but I am keeping him inside and taking him out on-leash. The one concern I have is thunderstorms. Could being scared of a thunderstorm be enough to get his blood pumping enough to cause a problem? He pants a lot when its storming but he doesn’t shake with fear. Normally he just goes in his dog house but being inside he won’t have his dog house (his comfort zone). We are supposed to have storms this week and I am worried. I did get some medication from our Vet but I hate to drug him if I don’t have to. I have our dog houses on our covered patio and he seems calmer out there where he can go in his dog house. I’m thinking about blocking off the entrance to the patio and letting him stay out there where he feels safer. I wanted to get your thoughts on whether being scared of storms could hurt him, and should I give him the medication or do you think just letting him stay on the patio where he feels safer be enough? Thank you again for your time.

  281. Doc says:

    Hello, Linda,
    The dog doesn’t have to lie still for six weeks. If he has thunderstorm anxiety, it won’t help things, but it’s not like hard aerobic exercise. I think your idea of letting him use his comfort zone dog-house and blocking off the patio is a good one. Use the meds if you have to. The main thing is to not let him run loose, nor to encourage vigorous play.

  282. Linda R. says:

    Thank you again for your response. He definitely will not be running loose. I don’t want to take any chances. I am going to let him go on the patio where he can get to the dog house. I think he’ll feel a lot safer there.

  283. Ny J. says:

    Hi. I rescued a now 9 month old pit bull 3 months ago. She was recently diagnosed with heartworms after taking preventative medicine for the past 3 months. The vet does not want to administer the Immiticide because she said my dog is too young and it may be too strong. Are there any other options for treatment that are just as effective? I’m not sure how far along she is, but the vet did mention there is a slight bulge in her chest, if this helps any to estimate the stage of the disease. I would love to just elect the surgery option, but it can be extremely costly. Please help.


  284. Doc says:

    Hello, Ny J.,
    That is totally bizarre. It takes heartworms six months to develop after the mosquito exposure, and seeing a positive blood test in a dog so young is very unusual. To have enough heartworms to cause clinical disease that would show up on an X-ray at this age is almost unbelievable.

    I have seen one dog with apparently zero resistance to the parasite die at 18 months, absolutely full of heartworms, but that was really a freak situation.

    Surgery to remove the heartworms is a last-ditch salvage effort for a dog dying with the post-caval syndrome form of the disease. NOT something that is recommended generally.

    I don’t know of any age limitations on the Immiticide. The most common side-effect is just soreness at the injection site (though that can be pretty severe for a day or two).

    DO stay on your heartworm preventive medication.

    The doctor seeing your dog is usually your best source of information. I can give only general information based on my own experience, and I have not seen your dog or your radiographs.

  285. georgia says:

    Hi we have a beautiful staffy x who we are fostering. When she came into care early January she sadly tested positive to heart worm. The poor girl was skin and bones, suffering from malnutrition, 3/4 of her hair was gone and her body was covered in weeping sores. Its been 3 months now, she’s 9kg heavier and her hair has grown back, and no more sores. She went in for her first heart worm injection last week (she’s been on heartworm meds since 9/01/2016), since then I have been told I must keep her in her crate and the only time she can come out is for on leash toilet breaks. I completely understand the entire heartworm treatment, but my worry is it’s only been a week in her crate and she’s showing signs of depression. She cries and cries sometimes and I can’t do anything for her, sometimes she just completely ignores me when I try and give her a cuddle. I’m worried what the worst case will be psychologically after beeing suck in her crate for 5 weeks! Please help, is their any warning signs I should be looking out for? And what can I do to make my baby girl happy??

  286. Matt says:

    Hi, my wife and I rescued a 6 year old Lab mix who is heart worm positive. We have started the Doxycycline and heart guard and are trying to limit activity. We make sure to only walk him on a leash and don’t let him run. However, I don’t think he is getting enough exercise and has been keeping us up all night barking. He has been getting 2 thirty minutes walks daily, and numerous trips to yard to pee. How much exercise is too much? He is a great dog, but my wife and I need some sleep. Thanks

  287. Doc says:

    Hello, Georgia,
    The goal of confinement is to keep the dog from exerting itself to the point of elevating the blood pressure. A big increase of blood pressure could shove the dead worms farther into the smaller arteries. This increases the chance of bleeding in the lungs.

    I cannot imagine keeping the dog in a crate for that length of time. We certainly don’t want her running loose around the yard, and especially would not wish her to escape the yard and run for hours.

    You should discuss this further with your veterinarian. If the dog is used to walking about inside the house, it is very unlikely that this would increase her chances of having complications with the treatment.

  288. Doc says:

    Hello, Matt,
    As long as the dog is walking and not running, or straining vigorously against the leash, he can walk all day. It is the vigorous activity, even in short bursts that increases the risk. Prolonged aerobic exercise carries the greatest risk, as he would do if he were allowed to run loose.

    You might talk to your veterinarian about using Benadryl to make him drowsy at night.

  289. Kelsi says:

    I have two dogs that tested lightly positive for heartworms. They received their first immiticide injection friday, april 1st. I have a pit mix, about 60 pounds, and a terrier mix, about 12 pounds. My 2 year old active terrier is strictly confined to a crate but my 7 year old pit just lays around the living room. It is April 3rd now and I’m concerned by my 7 year old, floyd. He is panting a lot, whining at some kind of pain, and can’t seem to lay down to sleep. I thought it might be the injection site but he doesn’t seem to care when I touch the area. He can’t jump on the couch without crying out in a lot of pain. He can be a “big baby” sometimes and he has an anxious type personality that makes him sensitive to changes. Could his anxiety make the treatment worse for him? They are on tramadol and prednisone. My terrier mix is acting like nothing is wrong even though she was the only one exhibiting symptons of HW, a heart murmur on right side of heart. I’m just really concerned for my older dog. If the first injection is this scary with him, I’m seriously dreading the last two.

  290. Doc says:

    Hello, Deb,
    Blood in the stool is never normal. It is also not a usual feature of treating a dog for heartworms. Other causes should be looked for: intestinal worms, intestinal infections, bleeding disorders, rodent poison, etc

  291. Doc says:

    Hello, Kelsi,

    It sounds like you are dealing with pain from the Immiticide injection, even though your dog doesn’t react to pressure on the injection site. This usually subsides within 48 hours, even without medication. If it lasts longer than that, it may be from another source.

    Usually we have good results with prednisone and tramadol. In cases where we don’t, I sometimes add acetaminophen, or acetaminophen plus codeine.

    You should consult your veterinarian before adding any medicines on your own here. Please DO NOT add any type of NSAID, such as ibuprofen or aleve, or even those approved for dogs, like Rimadyl. NSAIDs do not play well with prednisone.

  292. Sheri Anastasio says:

    Hello. My dog Chance just had his second injection for heartworm treatment today. He is home and seams to be pretty out of it and obviously in pain. He has a big ball size lump on each side of his back. Can I place cold pack’s on the site’s where it is swollen?

  293. Doc says:

    Hello, Sheri,
    Sorry I didn’t have the opportunity to get to this earlier.

    Cold packs would certainly have been appropriate. Cold causes blood vessels to shrink, slowing leakage of fluid, and reducing swelling. Heat has the opposite effect. Cold is indicated when something has just occurred. When it is longer term, heat increases the circulation and speeds healing. In the initial stages, it would promote more swelling.

    We routinely send home pain medicine with our heartworm treatment patients, even though 3 out of 4 clients can’t tell the dog needs it and don’t give it. There are certainly dogs that don’t seem to be bothered at all, and dogs that seem to be in very significant pain. Fortunately, that usually resolves within a couple of days, even with the really painful dogs.

  294. Sheri Anastasio says:

    I have been reading about the treatment. My dog just had his two shots. One on Monday and one on Tuesday. He was very sore yesterday and today at the injection sites. Now he is doing like this snoring sound and acting sometimes like he is having. Is this normal. I would have to drive tonight one and a half hours to the nearest 24 hour vet. ??????

  295. Doc says:

    Hello, Sheri,
    Soreness at the injection site is common, and the amount is unpredictable. Some dogs appear to have none at all, while others seem very painful. It usually subsides within a couple of days.
    I have not had any clients report the snoring sound or difficult breathing in the few days following injection.
    The worms do not usually shift position until they die, and this is several days later, as a rule. At that point, dogs often do feel bad: poor appetite, coughing, fever, sometimes difficult breathing, sometimes even coughing up blood.
    We usually send home pain medication at the time of the treatment. Please consult with your veterinarian about this. It is NOT safe to give ibuprofen or naproxen to dogs.

  296. Pauline Dunlop says:

    Hi, I came across this page trying to get info about a dog I have adopted from Romania. Hannah’s passport says she is 3yrs but my vet says she is closer to 10yrs. THAT is a huge difference.
    Hannah was HW+ but had treatment and got the all clear in December 2015. I adopted her in March 2016.
    I have noticed that she is quite weak in her rear right leg and cries out if any (even slight) pressure is put on the thigh.
    My vet has prescribed Loxicom as he diagnosed arthritis. However I have read articles about the heartworm treatment causing lasting pain in hind area.
    What is your experience of this and, if the treatment is potentially the cause, how long could this continue?
    Also, is Program Plus ok following her all-clear for HW?
    Thanks, Pauline. Scotland, UK

  297. Dave says:

    Fantastic information, I read through every post and feel quite a bit more confident about my rescue Rottie and his opportunity to get healthy! Thank you for taking the time to ease some of my fears and help me understand what is to come and what to look out for! You are appreciated!

  298. Doc says:

    Hello, Pauline,
    I have treated hundreds of dogs with Immiticide (melarsomine) to kill the heartworms. It is injected into the heavy muscle mass of the lower back. I often see soreness for a day or two after the injection. I have never seen a patient who had lasting pain in the hindquarters as a result. I would be interested in seeing the articles that talk about this, as I have never heard of it.

    Meloxicam is a non-steroidal anti-inflammatory pain reliever. It is generally used once daily, and if dosed appropriately is usually well tolerated. Dogs taking it long term should have periodic evaluation of kidney function.
    I would think that Program Plus would be fine (same stuff is sold in the USA under the trade name of Sentinel.

    It sounds to me like your veterinarian is doing a good job. You should share your concerns with him/her.

  299. Ny says:

    My 10 month old rescued pit gets her first Immiticide shot on Tuesday 5/24/16. Would it be ok to take her on a 4 hour car ride on Friday 5/27/16 for Memorial Day weekend so soon after her treatment?

  300. Doc says:

    Hello, Ny,

    It’s always best to consult with the doctor who is actually seeing and treating your dog.

    Generally speaking, I would not consider a car-ride to be a problem. It is physical exertion, with increased heart rate and blood pressure, that increases risk. If the dog enjoys the ride, I would not think that would complicate matters.

  301. maryellen says:

    My 6 year old westie was just diagnosed with hw today. She is a barker and last few months have noticed her bark has changes especially the very excited high pitched bark. It just comes out now as a high pitched squeak. My question is this a symptom related to the heartworm? Also after treatment does barking pose a problem in the lungs after the worms are killed off? She tends to bark out the window at everything that goes by and also barks quite a bit in the car.

  302. Doc says:

    Hello, Maryellen,
    A squeaky bark is not a typical sign of heart disease.

    Barking is pretty effortless for the dog, so does not require the type of exertion that would put stress on the blood vessels in the lungs.

    Annoying? Yes. Dangerous? No.

  303. penny says:

    Hello, I am fostering to adopt a 2 1/2 37 pd lab mix. She is such a loving little pooch. I am in love already. My question is. She has heart worm and she is currenlty being treated. I keep her in my bedroom with the air so she stays calm and cool. I do notice that she is panting even though it’s cool in the room. I am so worried after reading online about this illness. Is this panting normal. She is still eating, drinking. Do these pups live a normal life span after fighting off this disease? Thank you so much

  304. Doc says:

    Hello, Penny,
    A little panting wouldn’t worry me, but you should stay in touch with your veterinarian. I always prefer to recheck the dog if there is any doubt about how it is doing.

    Many dogs do live a normal lifespan after treatment. Some of this depends on how much damage has occurred already. With a small number of worms, and a dog who was feeling okay prior to treatment, I would expect a good long-term outcome.

  305. penny says:

    Thank you so much for getting back to me. I do have one more question. How long after treatment is started do I have to keep her caged up. Can she come out for short spurts into the family room with us? I got her from a shelter and have not spoken to a vet about her. The shelter deals with the vet due to I am just fostering her. Thank you so much.

  306. Doc says:

    Hello, Penny,
    Playing in the house should be fine. Walking on a leash should be fine.

    What you want to avoid is hard, aerobic exercise that raises her blood pressure, pushing dead worms farther into the blood vessels.

    No running loose, no frisbee chasing, etc.

  307. lauren says:

    I have a 11 year old german short hair that had heart worms she had the treatmemt 3 weeks ago, the week after she started coughing,gagging, not laying down having trouble breathing just like this article says! Dr put her on doxy and prednislone for 10 days.. she did better for a week than these sympotms came back she wont lay down she stands all day and night with her neck strecthed, coughing trouble breathing, how long does this go on for!!!

  308. Doc says:

    Hello, Lauren,
    Sorry I’m so late getting to my email.

    It usually takes 4 to 6 weeks for the dog’s body to dissolve the dead worms out of circulation.

    I have had the best luck with using prednisone for four weeks following treatment. We start with a fairly high dose, and taper down to a lower dose every 48 hours.

    If she is having respiratory distress, the doctor should be notified as soon as possible.

  309. Lisa says:

    We adopted an absolutely adorable 1 1/2 year old Heeler/Pit Mix in April 2016. He was a stray. He tested positive for HW. We started him on antibiotics for a month, followed by the 2 injection treatment, one month of calm, and prednisone. This was back in late Spring/early Summer. He has been on monthly Heartgard since. We slowly brought up his activity level after the one month period – back to full play/run in late June. Early July we had him neutered and a growth removed from his leg. No cardiac complications there, although he did pull out his stitches on the leg. My question is: he is a very, very energetic dog and when he engages in high activity play (and I mean high – chasing the ball, jumping in the air, running) he goes full throttle, when he stops to rest he is panting a lot. We didn’t really think this was unusual until we had him with my parent’s dog, they were both playing the same, and their dog wasn’t breathing at the same, fast rate as ours. Do different dogs just breathe differently? At rest, on walks, etc. he is completely normal. He isn’t coughing and is definitely not lethargic. We are supposed to bring him back this month for a 6 month/post treatment HW check, which we are doing soon.

  310. Doc says:

    Hello, Lisa,

    I think that dogs certainly have different levels of exercise tolerance. If he seems to feel well, has good energy, doesn’t get tired out and have to stop sooner than you think he should, I don’t think I’d worry much about that panting.

  311. Doc says:

    It is unlikely that this would happen with Immiticide. The manufacturer says that they chose the back muscle as the injection site as this gets the medicine into the bloodstream faster than any other location, without having to actually inject it directly into a vein.

    It is certainly possible that you might accidentally hit a vein doing an intramuscular injection. With an oil-based medicine, like some penicil