Demodectic mange is a skin disease caused by the massive proliferation and overgrowth in the skin of a microscopic parasite called Demodex canis. This mite is, in small numbers, part of the normal flora of the skin of most dogs, having been transmitted by the mother to the puppy in the very first days after birth.
The clinical signs of. Demodicosis occur when an incompetent or juvenile immune system allows the abnormal proliferation of parasites to occur. There may also be a genetic component to the disease (i.e. the tendency to get the disease can be inherited).
Animation of the parasite and its cycle:
The disease usually first appears in older pups, 3 to 12 months of age. However, adults dogs may also be affected; the infection then is often associated with another concomitant internal disease, or the administration of medication (e.g. corticosteroids) either of which may have weakened the immune system .
Importantly, demodectic mange is not contagious either between animals or to humans.
What are the clinical signs that I see?
There are two forms of demodectic mange:
1. Localized form:
We find multiple small and large areas of hair loss with inflamed skin, in various parts of the body, the head and legs being the most often affected. Usually, there is little or no itching, and the condition appears to be benign.
2. Generalized form:
The lesions are much more extensive and cover large parts of the body. Moreover, they are often aggravated by a secondary bacterial infection that will require antibiotic treatment in conjunction with and in addition to the treatment needed for the parasite itself. Itching, self-trauma and greater hair loss are typical in generalized demodicosis.
How will my veterinarian diagnose the problem?
The appearance of the lesions themselves is often typical and will usually be recognized by your veterinarian. Diagnosis is confirmed by a 'skin scraping' performed by taking a scalpel blade and gently scraping the actual skin lesion, and placing the debris on a slide for examination under a microscope. The observation of the parasite in this way is diagnostic.
Video of a microscope with the presence of Demodex:
What is the treatment ?
Generally, only the generalized disease requires treatment, though some veterinarians may treat the localized form with a topical ointment.
Different treatments are available, whether administered orally, or by topical application to the skin. Whatever acaricide product (a pharmaceutical which kills mites) is chosen by your veterinarian, it is essential not to rely solely on the apparent resolution of lesions to stop treatment, because the condition can recur. The medication should be administered for at least one month after getting several negative skin scrapings. If treatment is of insufficient duration, relapse of the demodicosis can occur, which can manifest itself in a few weeks to several months.
It is also recommended to spay (sterilize) female dogs suffering from generalized demodectic mange because hormonal changes related to heat or pregnancy may promote relapse. Also, given the hereditary tendency to develop the disease, it is essential to remove any dogs affected with the generalized form of the disease from a breeding program, to reduce the likelihood of later generations being affected.
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