demodectic mange and Ivermectin (Heartgard)

Demodectic mange is a very itchy condition caused by mites that live on the skin of dogs, cats, and people. When a dog’s immune system is challenged by stress, poor nutrition, or illness, the mite populations may boom, and mange is the result. There are localized forms of the condition with patchy hair loss only around the face or paws; in generalized mange, there may be spots on any part of the body. The condition is not contagious normally (it is different from sarcoptic mange), though puppies often are born with it. Pit bulls seem to be particularly vulnerable to demodectic mange, but any dog can get it.

The first line of treatment these days is Ivermectin. In low dose, this is the same thing as Heartgard, the popular heartworm medicine. For mange, Ivermectin liquid is administered daily, in higher dosage, for several weeks.

(Note: there may be no reason to administer Heartgard to dogs in our region at all, unless a dog is going to travel south, or has been exposed to a dog from south of Portland, OR.)

Unfortunately, there's a genetic mutation common in many herding breeds that causes dogs to have serious, sometimes life-threatening neurological symptoms in response to Ivermectin. Heelers are not included in the list, but collies, Australian Shepherds, and English Sheepdogs have high rates. The condition is more severe if inherited from both parents, while a milder form of the condition results from inheritance of the gene mutation from one parent. Even a half-herding breed mutt may have a significant risk of having the mild form of the condition. The condition also can be found at very low rates among other breeds.
The same mutation also confers sensitivity to a number of other drugs, including drugs used frequently in anesthesia for surgery.

For more information see:

http://www.marvistavet.com/html/body_demodectic_mange.html

Washington State University offers an easy genetic test for this condition. They will mail you a kit with instructions for free. You use the swabs provided to get cheek swab DNA samples from your dog, then mail them back to the lab with your $70 payment; results come back within two weeks.

http://www.vetmed.wsu.edu/depts-vcpl

Dr David Duclos, one of two board-licensed animal skin and allergy specialists in the western WA region, says that he would never administer Ivermectin to any dog without first getting the DNA test. Then, even if a dog tests negative, intolerance to Ivermectin is common, so he starts at low dose and works upward. Indeed, my Aussie mix dog tested negative for the genetic condition that causes neurological problems, but developed long-lasting diarrhea in response to a short course of Ivermectin that was not administered with the proper step-up approach.  My dog seemed to recover from her mange spontaneously, but had a relapse a couple of months later.  With a very planful stepping-up approach, she got through the entire many-weeks ivermectin treatment without any side effects.

The second choice treatment for demodectic mange is the drug amitraz, in the form of a rinse called Mitaban. Until recently, a preferred treatment was a spot-on flea remedy, Promeris, containing amitraz and another chemical. However, Promeris has been recalled due to adverse reactions. 

Mitaban is expensive when purchased from a vet, but very inexpensive when purchased in bulk online. Both Mitaban and Ivermectin may also be obtained at feed-and-seed stores much less expensively than at a vet clinic.