Update on Demodectic Mange
Demodectic mange is an inflammatory skin disease of primarily young dogs caused by the skin mite Demodex Canis. Mites are microscopic parasites that live in a variety of environments. The Demodectic mange mite lives beneath the skin around hair follicles. Diagnosis is made by making skin scrapings of suspicious areas of hair loss and examining the scraped skin under the microscope. In performing this test your veterinarian will deep skin scrape suspicious areas with a dull blade.
Dogs can manifest Demodectic mange in two forms: localized and generalized. The localized form, by far the most common, is manifested as small patches of hair loss around the face, head, and forelegs of dogs usually between four to twelve months of age. The majority of localized Demodicosis cases do not spread and recovery will occur in four to eight weeks with topical mite killing therapy or spontaneously with the help of the dog’s immune system. Approximately 5-10 percent of the localized cases progressively worsen to generalized in which large areas of the dog’s body shows hair loss, redness, inflammation and seborrhea. In time the skin becomes thickened, grey, easily bleeds, and loses its elasticity, thereby sagging and forming folds. Secondary bacterial infection frequently accompanies this disease.
Why and how do dogs develop localized and generalized Demodectic mange? The answer is controversial. Research has shown that the Demodex Canis mite occurs in limited numbers on the majority of healthy dogs where they feed on the hair follicle debris and surrounding cells. Puppies do not harbor the mites at whelping. It is theorized that they usually receive their initial exposure from an infested bitch during the first few days of life and perhaps even from one pup to another when in direct contact at this young age. Neither of these “carrier” animals shows any sign of the mites but can give it to a immature dog with an undeveloped immune system. At this time one or more triggering mechanisms appear essential for the parasites to proliferate beyond the capacity of the host and thereby produce clinical manifestations of the disease (hair loss and infected skin). An inherited defect in an animal’s immune system, cell-mediated immunodeficiency, is currently regarded as one factor that allows excessive proliferation of the mite population. Other predisposing factors that have been suggested include age, nutrition, stress, sebaceous gland size, hypothroidism, estrus, pregnancy, and abnormal environmental temperatures. There is no apparent predisposition regarding sex or hair length. To summarize, Demodicosis is probably not contagious, but is the result of mite exposure coupled with an immune deficiency, which prevents the host from mounting an immunological attack on the parasite.
The number one recommended treatment for Demodectic mange is a sponge-on dip called Mitaban, made by Pharmacia Upjohn. In brief, treatment involves washing the dog in a medicated shampoo designed to kill bacteria and remove scales and exudate, followed by a sponge-on application of the Mitaban to the entire body. Over 85 percent of all cases completely recover with four to eight topical sponge-on baths. Of the remaining 14 percent, half can be kept in good condition by periodic maintenance treatments every two, four, or eight weeks or alternative treatments. In most cases regrowth of hair and return of skin to a healthy state is rapid.
