Demodex mange, as the condition is commonly called, is caused by microscopic mites that live in glands within the skin and in the hair follicles of most mammals. (On humans, they are commonly found in the eyebrow region.) All stages of life occur on the host; the period from egg to adult is two to four weeks. The mites are transmitted from one mammal to another by direct contact; however, the condition itself is not contagious.

The mange mites cause problems for the host only when they proliferate in numbers large enough to cause a condition called demodicosis, which involves damage to the skin in the form of lesions and bare patches where hair is lost. Contrary to what one might expect, the bare patches and lesions are not accompanied by itchiness.

The underlying causes of demodicosis appear to vary for different levels of severity of the disease. Basically, the proliferation of the mites occurs when the victim’s immune system is deficient, which may be (but is not necessarily) the result of a genetic defect. The levels of severity include:

1) Localized – Hair loss is generally limited to the areas of the muzzle, face and forelimbs. Possibly induced by stress from causes such as puberty(5-9 months), surgery, pregnancy or a nutritional deficiency. The tendency toward localized outbreaks may be inherited. The symptoms in these cases usually disappear (with or without treatment) in 4 to 8 weeks.

2) Generalized – Hair loss is extensive and may occur anywhere on the body. In young dogs, the probable cause is a genetic deficiency that keeps the immune system from functioning properly and allows the mites to proliferate excessively. It is highly likely that dogs with this deficiency would pass it on to their descendants, who would probably also suffer from demodicosis or other disorders related to the immune system.

Generalized cases that begin in adult dogs seem to be caused by a concurrent disease such as cancer that weakens the immune system or by the use of immunosuppressive drugs such as corticosteroids. The development of demodicosis in an adult dog is a sign that all is not well with the dog, but is not necessarily a predictor of whether the descendants might develop the condition. However, if such a dog is still of breeding age, the owner should consider that the condition that caused the immune system to be stressed or that required treatment with immunosuppressives might well be hereditary, and, therefore, a reason for not breeding.

The presence of the mites can be diagnosed by viewing skin scrapings from the lesions under a microscope. Since the mites can be difficult to detect, the lack of a positive diagnosis is not definitive.

Treatment of generalized cases can be lengthy, with progress being made very slowly. One treatment recommended frequently is to give bi-weekly Mitaban dips. Shaving the dog can help to make the Mitaban treatments more successful. This treatment program is not ideal, as Mitaban is a strong chemical agent that may produce harmful side effects. In extreme cases that have not responded to treatment, Mitaban may be applied on a daily basis but to no more than one-half the skin area.

Some generalized cases have been treated successfully with large daily doses of heartworm preventatives containing Ivermectin or Milbemycin. (Examples of brand names are Interceptor and Heartgard). One owner reported that no side effects were experienced from using Interceptor, and the condition was completely cleared up within six months. Ivermectin is less expensive than Milbemycin, but will interact unfavorably with other drugs such as diazapem, and is particularly harmful to some breeds of herding dogs.

Secondary skin infections that may accompany an outbreak of demodicosis can usually be treated successfully with antibiotics.

Editors Note: In some cases a Vet can mis diagnose the secondary infections as the cause of the problem rather than the result and try to treat with antibiotics. Usually the treatment will appear to be working, but the condition will return as soon as the drugs are discontinued.

Credits: Most of the information above was compiled from postings to the bulldog-fx mailing list during the last week in February 1998, and the berner-l mailing list, digest numbers 1105 and 1106. Treatment recommendations are from an article titled “Systemic therapy for generalized canine demodicosis” written by Michael G. Charach and published in the Canadian Veterinary Journal, November 1995.