So here's a follow-up to the case of Ellie Mae. I promised pictures and follow-up, and here we are.
The treatment of choice for dogs with demodectic mange is daily dosing with 400 to 600 mcg/kg of ivermectin. The problem for Ellie Mae is that many Collies carry the MDR1 gene mutation, and these dogs cannot take that kind of ivermectin dose. The low dose in Heartgard-30 is fine for them, but the humongo doses needed to treat demodex may kill dogs who carry the MDR1 gene mutation.
Not all Collies have the gene mutation, and you can test for it, so that's what we did. While waiting for our test results, we started Ellie Mae on daily milbemyin (Interceptor – same dose daily as for monthly heartworm prevention – effective but pricey). I had to order my DNA test kit (and now you can send blood samples, as well as cheek swabs), so I couldn't send the test off right away. I thought that the dog would still look bad enough for my "before" picture when she came back for the test, but it was 12 days before the kit came. After 12 days of treatment she was already dramatically improved.
Day 22 – we get the bad news. Ellie Mae DOES have the MDR1 mutation, and cannot safely take the big doses of ivermectin (inexpensive) and our best bet is to continue the oral milbemycin.
The neck is still a little crusty, but mucho improved. The skin infection is pretty much gone. We're down to bathing the bad spots with benzoyl peroxide shampoo (SulfOxydex) and giving the oral milbemycin.
How long will she get treated? Until she looks completely normal. Then I'll shave a spot and do another skin scraping. If I find mites, we'll continue treatment for two more weeks and check again. When we can't find mites, we'll treat for two more weeks. Then we'll call it good (and hope it is good).
How are these people affording daily Interceptor? Well, you know what they say: it's an ill wind that blows nobody good. A while back, we over-purchased on boxes of Interceptor single doses — the "bulk pack". We didn't use it before it went out of date. So here I am with a box of expensive tablets that I can't send back, and I can't sell. They're sure too good to throw away, though. That's what Ellie Mae is taking. My bad inventory management is her good fortune.