By Dr. Mike Aushwitz - Kuenzi Family Pet Hospital, Waukesha, WI
The microscopic mite, Sarcoptic scabies, causes sarcoptic mange, also known as scabies or the mange. The mite causes intense itching by actually burrowing under the skin in the outer cornified layers, where it causes an intense inflammatory reaction. The infection is most common in domestic and wild canines; however, cats, pigs, and other farm animals have their varieties of mange mites that cause problems in these species. People are also susceptible to scabies, acquiring the mite from an outside source or via zoonotic infection.
The classic case of scabies is seen in stray dogs or dogs coming from crowded unsanitary kennels, though this does not explain the majority of cases we see, and in fact, often cannot explain where the dog acquired the infection. Scabies is, without a doubt, the itchiest skin condition a dog can get. Intense allergic skin disease and flea allergy dermatitis might come close, but scabies always wins.
The itch is constant and intense, affecting most of the dog’s body, though the tips of the ears, forearms (legs), elbow area, and groin area seem to be most commonly affected. The dog often has a “mangy” look in the end stages of the infection characterized by self-induced hair loss from biting/itching, inflamed skin, and excessive crust and scale at the site of the lesions. The animal often is not feeling well and may not be eating well. In addition, the itch is not satisfied by traditional allergy medication including antihistamines, steroids, and topicals.
Clinical signs, history, and demonstration of the mite under the microscope diagnose the disease. Skin scrapings using a scalpel blade are performed to try to demonstrate the mite. Very often the mite can be difficult to find despite multiple attempts at skin scrapings. In some cases, if the clinical signs and history are suggestive of scabies, but no mites can be found, a therapeutic trial is initiated, and if the dog responds, the diagnosis of scabies can be made. Fortunately, treatment is effective and prognosis is generally excellent for recovery.
Several treatments are available, Ivermectin injection being the most convenient. Usually, two to three injections given two weeks apart do the trick. Other options include various scabicidal dips and a topical spot-on called Revolution, which among other things, is licensed for treating scabies. I have tried Revolution in several cases unsuccessfully, and find the Ivermectin injections most successful and convenient for the owner. In addition, antihistamine, low dose steroids, and/or shampoos are used to diminish the degree of itch during the course of the injection.