Scabies & Mange
The word “MANGE” is enough to make most people shudder. When a dog has “mange”, it means they are infected with microscopic creatures known as mites. There is more than one type of mange, but this discussion focuses solely on scabies mange (fancy name: Sarcoptes scabiei var. canis), a highly contagious, intensely itchy skin disease.
No dog is immune. Any age or breed dog can be infected. Cats, on the other hand, are thought to be resistant, although a few rare cases have existed. A dog can be infected any time of year. In a multi-dog household, multiple pets are usually affected. One can start before the others, or be more affected than the others.
Hairloss, crusting, and irritation often begins on the elbows, ear tips, “ankles”, chest, and belly. With disease progression, the entire body will get affected. A common finding is heavily crusted ear tips, with healthy ear canals. A history of sudden onset, intense itching not responsive to steroids is classic for scabies mange. Affected pets scratch, lick, and bite themselves like crazy.
You don’t have to have a filthy house or yard for your dog to contract mange. Sarcoptic mange is extremely contagious, and is easily contracted from direct contact with an infected dog, or indirect contact with fox feces, mite infested fur, or crusts in the environment. A variety of canine species are affected: fox, wolves, and coyotes. If wildlife crosses through your yard (think “urban expansion”), or you take your dog to the dog park or any other location where lots of other dogs visit, any of these places could be potential sources of contamination.
Here lies the problem. A superficial skin scraping is the “official” test used. A surgical bladed is scraped back and forth to collect the superficial layer of skin (and hopefully some scabies mites or eggs) and examined under the microscope. If big fat scabies mites (I think they look like sumo wrestlers) show up, then—great!—you’ve got your diagnosis. If the slide is “negative” (no mites seen), scabies is still quite possible because skin scrapings are positive in only 20% of cases of scabies disease.
Therefore, patients are often treated for mange if they present with a history and lesions highly suspicious of scabies mange. A history of sudden onset, intense itching nonresponsive to steroids is classic for scabies mange. Often the diagnosis of scabies disease comes later—after a favorable response to treatment.
Treatment of scabies mange has improved greatly since the days of amitraz or lime sulfur dips, which were prone to unpleasant side effects and treatment failure. Today, scabies mange is typically treated with injections of ivermectin (the same drug used to prevent heartworm disease, but at a much higher dose), every two weeks for 3 total treatments. Except when a case has been chronic, then more injections may be necessary.
Treatment becomes less straight forward when herding dogs are involved—such as Collies, Shetland sheepdogs, old English sheepdogs, Australian shepherds, or any crossbreeds. Herding breeds can carry a genetic mutation which makes them intolerant of numerous drugs, including ivermectin. A blood test can determine if an individual carries this mutation.
Interceptor (milbemycin) was safely used in collies with scabies mange until the company stopped making it. As of April 2013, Sentinel (milbemycin + lufeneron) is supposedly making a come-back. For the sake of scabies treatment and heartworm prevention, let’s hope the rumors are true.
If the skin lesions have become infected or heavily crusted, oral antibiotics and medicated shampoos may be necessary to treat secondary bacterial infections.
Usually, improvements in comfort and skin coat are seen within 1-3 weeks after starting the ivermectin injections, but it can take longer for full resolution. Reinfection is possible if the patient is repeatedly exposed to scabies mites. In these cases, preventative treatment with topical Revolution (selamectin) is recommended. This is yet another drug that can’t be used in many Collie-type herding breeds.
All in-contact dogs need to be treated. Again, cats are thought to be resistant. Dermatologists typically recommend to only treat cats who are showing signs of scratching, hairloss, and skin irritation.
Scabies mange is zoonotic, meaning that people can get it. Since we are poor hosts for these mites, they usually die off quickly, but some people can be severely affected, either due to hypersensitization or immunosuppression.
Opinions on whether or not the environment needs to be cleaned vary between dermatologists. In my opinion, since scabies mites can live up to 3 weeks off the hosts in crusts, and people can be affected (although they often aren’t), I recommend thoroughly cleaning the environment to remove any possible contamination. It just makes sense to me to do a good job mopping and vacuuming to avoid prolonging the discomfort of the pets and to potentially avoid the discomfort of the humans in the household.
-Dr. Ann M. Anderson