Demodectic Mange in Cats

 

Demodectic mange mites are normal skin residents in the hair follicles of all species. They live in balance with their host’s immune system, but if the balance shifts in favor of the mite, skin disease results. The nature of the skin disease can be quite variable, ranging from over-grooming (also called fur mowing) to the raw, weepy lesions of eosinophilic granuloma complex, to the dry seed-like scabs commonly referred to as miliary dermatitis.

Demodectic mange in dogs is extremely common, especially in puppies. Demodicosis in cats is much more unusual.

Cats have Two Types of Demodex Mites

Demodex cati and Demodex gatoi are the two Demodex mites of cata. (Dogs have only Demodex canis to address.) Demodex cati is long and slender like the “alligator-esque” canine mite and like the canine mite lives inside hair follicles. Demodex gatoi is short, stubby with hardly any tail at all, and lives more superficially in the skin. Demodex cati is felt to be a normal resident of feline skin while Demodex gatoi is more likely an infectious agent.

Because this is not a common condition, only a limited number of cases have been published, and much extrapolation from the canine condition is necessary. Some sort of immune suppression appears to be a pre-requisite to infection for both mites (as is the case with dogs). Unlike the canine situation, there is some reason to think that Demodex gatoi may be transmissible between individuals. Demodex gatoi infection appears to be slightly more common than infection with Demodex cati, and is noted for extreme itchiness.

Diagnosis

A skin scraping is necessary to detect these mites, though they are not as easily seen nor present in obviously large numbers as the canine mites are. Part of the problem is that Demodex gatoi mites reside superficially in the skin and are readily licked away by an itchy cat. The fact that this condition is so rare (and thus unexpected) is probably the chief impediment to making the diagnosis.

Treatment

Fortunately, after the diagnosis is made, treatment is not difficult. Lime sulfur dips are smelly but effective when given every 5 to 7 days for six dips, but do not discontinue dipping until the skin scrapes are negative. The dip should not be rinsed off the cat. Dips are extremely stinky, and will discolor jewelry and towels as well as light colored fur; it may be preferable to have the veterinary hospital perform the dipping.

As an alternative, ivermectin can be used on a daily or every other day basis. The problem with this treatment is that ivermectin is generally diluted in propylene glycol, which can cause the formation of abnormal red blood cells in cats. For this reason, lime sulfur dips are the treatment of choice. Treatment is continued until scrapes are negative for Demodex cati and for two weeks beyond apparent cure for Demodex gatoi.

If Demodex gatoi has been identified, all cats in the household must be treated as the mite is felt to be contagious. Bedding and toys should also be cleaned.

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