Demodectic mange is the result of Demodex canis, a microscopic mite multiplying out of control. Most dogs have demodex mites on their skin in small numbers. These mites are acquired by puppies shortly after birth, from their mother.
The causative factors as to why some dogs develope demodectic mange while other dogs do not is not fully understood. The tendancy to be suseptible to demodectic mange appears to be hereditary. It is known that dogs with demodectic mange have an immune system defect. It is this defect that appears to be inherited, making the pup unable to keep the demodex mites under control.
Demodectic mange occurs in one of two forms. The first form is the localized form. This form most often appears in dogs under 1 year of age. The first sign is a thinning of hair around the eyelids, the lips, the corners of the mouth and the front legs. The dog has a moth-eaten appearance. The patches of hair loss can progress into circles of approximately one inch in diameter (occasionally confused with ringworm). Mite removal/reduction normally consists of cleansing shampoos, antibiotic therapy, and immune stimulants. Not all young animals that experience demodicosis are immunologically impaired for life. A significant percentage will "self cure" as their immune system matures. This maturity normally takes place between the ages of 8 months and 3 years, depending on the breed of dog.
During treatment it is critical that the dog is making continuous improvement. If the animal has 5 or more patches, or is not showing a marked improvement; the demodex could be progressing into the generalized form.
The generalized form is the second presentation type of this condition. Generalized demodex can begin as a localized case or can present itself as a sudden onset. Numerous patches appear on the head, legs, and trunk. These patches continuously spread developing into large areas of hair loss. The hair follicles become congested with debris and mites. The breakdown of the skin leads to the formation of sores, with crusting and draining sinus tracts.
Treatment of dogs experiencing generalized demodex can be very prolonged. The reponse to treatment is slow and often requires frequent changes in the medication. In spite of the number of mite removal dips, topical ointments and antibiotics availale a cure is not always possible. Generalized demodectic mange must be treated under veterinary supervision.
Older dogs that develop demodectic mange (in either form) should be screened for underlying causative factors in immune system dysfunction. Diseases such as diabetes, cancer or Cushing's disease can all impact therapy.
Dogs treated for generalized demodectic mange should be neutered