You may have heard the term “mange” used to describe various types of skin problems, but what does a diagnosis of mange really mean? Mange is a layman’s term used to describe a mite infestation. The two most common types of mange seen in dogs are Demodectic mange (demodicosis) and Sarcoptic mange (scabies).
Demodectic mange is an overgrowth of Demodex mites. Symptoms include hair loss, comedones (blackheads), redness of the skin, and sometimes scabs and pimples. In severe cases we can see swelling, oozing, bleeding skin lesions, and enlarged lymph nodes. Demodex canis and Demodex injai are the mite species most commonly involved in canine demodicosis, and they reside in the hair follicles and sebaceous glands in the skin. All dogs have a small resident population of Demodex mites; colonization from mites living on the mother’s skin occurs in puppies shortly after birth. Most of the time, the dog’s immune system keeps the mite population in check, and there is no resulting skin disease. In certain situations, the immune system is no longer able to control the mite population and we see mite overgrowth and skin disease. Fortunately Demodex mites are species specific – canine demodicosis is not contagious to humans!
There are two forms of demodicosis- localized and generalized. The definition is somewhat flexible, but in general we consider the disease to be localized if there are 5 or fewer focal lesions on the body, otherwise it is considered generalized disease. The disease can also be classified based on the age of onset – juvenile onset demodicosis occurs in dogs around a year of age or less. If the disease symptoms begin later in life we consider it to be adult onset demodicosis.
The diagnosis of demodectic mange is made by finding mites on skin scrapings. Treatment of Demodicosis is evolving dramatically. In the past, medications like amitraz (applied topically as a medicated dip) and ivermectin were the mainstays of therapy. Both of these medications have potential to cause significant toxic side effects in some patients. Bravecto (fluralaner; Merck), NexGard (afoxolaner; Merial), and Simparica (sarolaner; Zoetis) are isoxazolines – these three products are safe, effective, and FDA approved medications for oral administration to dogs for prevention of fleas and ticks. Recent research has shown that the isoxazolines also have anti-Demodex mite activity.
Sarcoptic mange, or scabies is the type of mange that gives us the “creepy crawlies.” Scabies is caused by an infestation of the mite Sarcoptes scabiei var. canis. Scabies mites live in the superficial layers of the epidermis and are highly contagious between dogs! Sarcoptes scabiei var. canis prefers a canid host, however these mites can transiently infest and cause symptoms in some humans. Scabies mites are typically contracted from direct or indirect contact with other dogs or wildlife such as coyotes and foxes. Symptoms of scabies include moderate to severe itching, hair loss, scaly skin, redness, and crusting. The ear margins, elbows, and hocks (ankles) are sites where we often see skin lesions in dogs with Sarcoptic mange, however the lesions can be generalized.
The diagnosis of Sarcoptic mange is confirmed by finding mites on skin scrapings, however these mites can be difficult to find, and dramatic skin disease can be caused by a very low number of mites. Because of this, we often treat dogs for scabies based on clinical suspicion. The only way to 100% rule out scabies is to treat the dog! When treating for scabies, all dogs in the household must be treated in order to eliminate the infestation. Some dogs do not display significant clinical symptoms even when carrying scabies mites, so it is critical to treat all household dogs regardless of whether or not they seem itchy.
Revolution (selamectin; Zoetis) is a safe and effective topical medication that is FDA approved for prevention of fleas and heartworm and the treatment of Sarcoptic mange in dogs. At this time, Revolution is our mainstay of treatment for dogs with scabies, however with the release of the isoxazolines as discussed above for demodicosis, we may someday have evidence that these drugs could be used for treatment of scabies as well.