Demodectic mange mites live in the hair follicles of all species as normal skin residents. 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 raw weepy eosinophilic granuloma complex lesions to the dry seedlike scabs commonly referred to as "miliary dermatitis."

Demodectic mange in the dog is extremely common, especially in puppies. Demodicosis in the cat is much more unusual and this article will feature the differences.

THERE ARE TWO TYPES OF DEMODEX MITES IN THE CAT

Demodex cati and Demodex gatoi are the two demodex mites of the cat. (The dog has only Demodex canis to address.) Demodex cati is long and slender like the “alligator-esque” canine mite and lives inside hair follicles also like the canine mite while Demodex gatoi is short, stubby with hardly has 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.

Demodex cati Demodex gatoi

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 the dog). 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 that 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 the obvious 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 5-7 days for six dips though one should not discontinue dipping until skin scrapes are negative. The dip should not be rinsed off the cat. Dips are extremely stinky, will discolor jewelry and towels as well as light colored fur; it may be preferable to have the vet hospital perform the dipping.

As an alternative, ivermectin can be used on a daily or every other day basis. The problem wi th this treatment is that ivermectin is generally diluted in propylene glycol which can cause the formation of abnormal red blood cells in the cat. 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.

Page last updated: 6/17/10