Demodicosis, also called red mange or Demodex, is a skin disease caused by Demodex canis, a cigar-shaped microscopic mite that is a normal inhabitant of canine skin and found on most healthy dogs. The mite infests hair follicles and occasionally the sebaceous glands of the skin. When present in excess numbers, the mite causes demodicosis, also called demodectic mange.
What Is Mange?
Mange is a generic term that describes a hair loss and skin condition caused by microscopic parasites, called mites, that live on or in the skin. Mites are similar to insects but are more closely related to spiders.
For instance, canine scabies is another type of mange mite of dogs. Ear mites are another parasite that lives inside the ear canal. Mange is caused by a wide variety of mites, and depending on the mite involved, skin disease can be mild to severe. It may resemble some types of skin allergies.
Causes of Mange
Demodicosis is not contagious. Puppies are infected the first two or three days after birth through close contact with an infected mother. In normal dogs, a few of these mites may be found in the hair follicles of the face. A normal immune system keeps the mite population in check so that no disease results and the puppy's hair coat remains normal.
The life cycle of the mite is spent entirely in the host animal and takes about 20 to 35 days to complete. Spindle-shaped eggs hatch into small, six-legged larvae, which molt into eight-legged nymphs, and then into eight-legged adults.
Demodicosis typically affects puppies 3 to 12 months old. Usually, it is the immune-compromised individual unable to stop mite proliferation that develops the disease. Two forms of demodectic mange occur, localized and generalized.
The condition always begins as the localized form, which is limited to a spot or two on the face and legs. Localized demodicosis is quite common in puppies, and it is usually a mild disease that goes away by itself. It typically consists of one to five small, circular, red and scaly areas of hair loss around the eyes and lips, or on the forelegs. The lesions may or may not be itchy.
In most cases, the localized form resolves as the dog's immune system matures and gets the bugs under control. It rarely recurs. An adult-onset disease is considered rare, and when it does occur, it usually is a result of compromised immunity associated with other systemic diseases like Cushing's disease or cancer.
When the localized form spreads, involving large areas of the body with severe disease, it is termed generalized demodicosis. Generalized demodicosis is considered uncommon. It most often occurs in youngsters, usually before the age of 18 months. Such dogs may have a genetic defect in their immune system.
Any dog may develop the disease, but an inherited predisposition appears to increase the incidence of the disease in the Afghan hound, American Staffordshire terrier, Boston terrier, boxer, Chihuahua, Chinese shar-pei, collie, Dalmatian, Doberman Pinscher, English bulldog, German shepherd dog, Great Dane, Old English sheepdog, pit bull terrier, and pug.
Generalized demodicosis is a severe disease characterized by massive patchy or generalized hair loss and skin inflammation, often complicated by a bacterial infection that may cause the feet to swell. Mites (all stages) may also be found in lymph nodes, intestinal wall, blood, spleen, liver, kidney, bladder, lung, urine, and feces. The skin is red, crusty and warm, and has many pustules. It bleeds easily, becomes very tender, and has a strong "mousy" odor due to bacterial infection on the skin. The condition can ultimately kill the puppy.
Diagnosing and Treating Demodicosis
Diagnosis is based on signs of the disease and finding the parasite in skin scrapings or biopsies. Occasionally treatment is not necessary for localized demodicosis, which may clear up by itself.
Generalized demodicosis requires aggressive therapy, however. Typically, the pup is shaved to offer better access to the skin and is given weekly or every-other-week whole-body dips with a miticidal preparation prescribed by the veterinarian. Some puppies and breeds are sensitive to these preparations, though, and may suffer side effects such as drowsiness, vomiting, lethargy, and drunken behavior. Use such products only with veterinary supervision.
Antibiotic therapy is required to fight secondary infections. Repeated baths with exfoliating shampoos such as those containing benzoyl peroxide are helpful.
Unfortunately, dogs suffering from generalized demodicosis have a guarded prognosis and may never achieve a cure. Euthanasia is sometimes the kindest choice. Because of the potential heritable components involved in this disease, dogs that have suffered generalized demodicosis should not be bred.