Zoonotic Ectoparasites

I started to put this under "Strange Beliefs".  People think that veterinarians know everything. Somewhere between the Encyclopedia Britannica and Google, the veterinarian was(is) the resource to rely on.  I’ve been called at night by a person wanting to know if polar bears eat penguins or fish (polar bears=North pole, penguins=South pole — trick question; they eat seals…and eskimos).  People whose children have been bitten by dogs call me instead of the pediatrician.  Physicians call me to ask what should be done with the dog that has bitten someone. "Is the dog all right?"

Then there was the question of how elephants make love, which is not a G-rated story, I’m afraid.  It makes good performance art for a mature audience, though.

A zoonosis is a disease shared by animals and people. You could have it and your pet could catch it, or vice versa.  Fortunately there aren’t a lot of really common ones.  An ectoparasite is some unwanted little creature that lives on your outsides (versus worms, which are on your insides, i.e. endoparasites).  In today’s episode, we are referring primarily to bugs (a term which I love, as it includes both the six-legged family of insects, and the eight-legged family of arachnids, ticks, mites, lice, etcetera, as well as various indeterminate species which may or may not exist, such as cooties).

A hundred years ago or so, fleas were a commonplace of everyday life for people.  Folks didn’t bathe often, and they didn’t change or wash their clothes very often.  They were such an integral part of human existence that men even wrote seductive poems about fleas, as in this one by John Donne: "Marke but this flea, and marke in this/ How little which  thou deny’st me is,/ It sucked me first, and now sucks thee./  And in this flea our two bloods mingled be."  Pretty romantic, huh?

You could still pick up a few fleas if you share a bed with a flea-infested pet, but you don’t have enough fur for them to hide really well, plus there’s that bathing thing.

The dog scabies mite Sarcops scabei can be transferred to humans.  It is not the same bug as the human scabies mite, and cannot live long in human flesh.  It feels like "Chiggers Gone Wild", terribly itchy, but doesn’t live and reproduce indefinitely like it does in the dog’s skin.  You get over it spontaneously in a few (very itchy) days.  The mites cannot live more than 48 hours off the dog, so one rarely acquires it from contaminated furniture and so forth. Handling an infested dog a lot (or sleeping with it) can certainly get you infected.  You see little red bumps, looking much like the rash produced by chiggers, and they are most likely to congregrate where your clothing is tight (also like chiggers).

Head lice cannot be carried by pets.  The human head louse has tiny pincers adapted to the fine hairs of the human head, and they just cannot hang on to the coarser hairs of the pet.  If you’ve got head lice, quit sharing your comb and be sure you’ve got your own hat when you leave the party.  This is a good place to stop the explanation, and this is how I know:

A lady brought several of the little bugs in a ziploc bag for me to identify once.  "My daughter has these bugs in her hair, and she puts the cat on her head a lot [Which makes a great mental picture], and I thought she might have gotten them from the cat."  I identified the mite and explained why the cat could not be the culprit, but I didn’t stop there.  I then proceeded to theorize that "…She probably got them at day-care."…beat…beat…beat…"I run a day-care in my home."   There is a time to talk, and a time to shut up, which I often do not correctly identify.

The crab louse (pubic louse) can be harbored temporarily by dogs and cats, due to the larger pincers they carry for hanging on to coarser hairs.  I have seen these on dogs twice.  Only one of the dogs was a stray.  I was able to figure out the time to shut up pretty quickly on that one.

Yesterday I had the interesting experience of being asked to identify bugs that were infesting a whole family who had been afflicted for eight months.  "It all started when my wife’s brother stayed with us.  He was itching, and after he left, we all started itching.  He used our car, and every time we get in the car we break out again.  Show him your belly, honey."  It was on her arms, too.  Their first physician had just backed out of the room, making the sign of the cross and telling them they had scabies.  They believe (and I’m not disputing it) that when they scratch or squeeze, little black bugs emerge from their skin.  They had (they believed) captured several of these and immobilized them in scotch tape.  With their own microscope (the Gilbert science kit variety) they believed that they had identified Chorioptes.  When they delivered the specimens to their doctor, he pronounced their trophies to be merely balls of lint.  Tiny balls of lint, to be sure, but lint none the less.  I was forced to concur.  After examining twelve of their specimens, I assured the gentleman that I did not doubt him, but that the specimens were not identifiable.  I supplied him with microscope slides and instructions for specimen preparation, and assured him that I would be happy to evaluate any new specimens.  Truthfully, the history suggests bedbug infestation (which, by the way, is a serious problem in several upscale New York City hotels, as reported in the Wall Street Journal some time ago).  I’d love to make that diagnosis.  It would be cool to help the people out (and one-up their physician, not that I’m that petty, you understand).

Here is the kicker:  these people do not own a pet.  They just came to me because veterinarians know everything.