Demodectic mange is a skin condition caused by a microscopic mite that lives in the hair follicle. A small number of Demodex mites live in the skin of most dogs without causing any problem. When a dogs immune system is compromised due to illness, parasites, or poor nutrition, Demodex mites can multiply rapidly. It is especially common in young dogs. The overgrowth of mites damages the hair follicle, resulting in hair loss and skin irritation.
The first sign is one or more small patches of hair loss. These can occur anywhere on the body, but the most common areas are the face, ears, and front legs. The skin in these areas may become reddish or crusty, but is not itchy. Most cases of demodectic mange never progress beyond this stage, which is called localized demodecosis.
Generalized demodecosis is a more serious condition, in which the areas of hair loss and skin injury cover much of the body. Dogs with generalized demodecosis usually have very weak immune systems, so it may take much longer for them to recover. The damaged skin is also very susceptible to infection. Bacteria, yeasts, and other microbes that normally exist in the environment can invade the skin and internal tissues. These secondary infections can be serious, even life-threatening.
Although the areas of hair loss may lead the veterinarian to suspect demodectic mange, the final diagnosis is made by performing a skin scraping test. The skin is scraped in several areas to loosen cells and mites which are then examined microscopically. Large numbers of Demodex mites are seen in most cases. Occasionally, the mites are more difficult to find, requiring repeated testing. Other tests may be performed to make sure the hair loss is not due to a cause other than mites.
The veterinarian will select the treatment plan based on the condition of the dog and the severity of the skin condition. Treatments may include skin creams, dips, or medications given by mouth or by injection. In cases of generalized mange, antibiotics and other treatments may be required as well. The length of treatment varies depending on the unique ability of each dog to recover. It may range from weeks to months or more. Follow-up skin scraping tests will be performed to confirm full recovery.
Because the Demodex mite is normally present in all dogs in small quantities, the condition is not contagious to other pets or to people.