Cat Mites And Feline Demodectic Mange

Demodectic mange, also known as demodicosis, is a skin disease caused by Demodex mites, which are found worldwide and on many animal species, including cats.

Demodectic mange in cats is caused by Demodex cati (Demodex folliculorum var. cati) and Demodex gatoi, a short stubby form of the mite. Clinical demodicosis is frequent in dogs but uncommon in cats, while human infection from dogs or cats is rare.

Adult Demodex mites are cigar-shaped, up to 0.3mm long, with eight blunt legs each with claws at the end. The stunted legs reflect the fact that the mites do not walk about on the host nearly as much as other types of mites. Its head boasts large protruding jaws to feed on skin debris. The body of the mite is covered with a hard outer skeleton, called the cuticle, which appears wrinkled.

Demodex mites reside in hair follicles, and occasionally sebaceous (oil) or sweat glands in the skin, where they spend their entire lives. The adult male and female mites mate and lay eggs in these glands. Unlike the other mites, Demodex eggs are cigar shaped. They hatch into six-legged larvae which molt into eight-legged nymphs, then molt again into adults. The life cycle is completed between 18 and 24 days.

Treatment warning
Amitraz, which is very effective in dogs with mites, should not be used in cats. It is not FDA-approved and the side effects of this medication can be serious, even resulting in death of the affected cat.

Clinical disease in cats is rare. Lesions occur on the head and in the ear canal and involve hair loss, inflammation, scaling and itching. The disease in cats is thought to be associated most commonly with feline AIDS (FIV), which suppresses the cat's immune system and allows the small numbers of mites normally present in the skin to proliferate. D.cati inhabits the hair follicles and is not easily transmitted, however, D. gatoi resides on the skin surface and may be transmissible between cats, like other forms of mange.

"The disease in cats is thought to be associated most commonly with feline AIDS (FIV), which suppresses the cat's immune system."

Diagnosis of feline demodex is most commonly by demonstration of mites in deep skin scrapings, which may require sedation or general anesthesia.

Because D. cati mites live deep in the hair follicle, the veterinarian will often squeeze the skin (like a pimple) before scraping in an attempt to push mites out from the follicles. The hair is usually clipped from the site, then a scalpel blade doused with a little mineral oil is scraped across the skin until it just begins to bleed. The skin and debris collected on the scalpel blade are wiped onto a slide and examined under a microscope by the veterinarian.

It is possible that no mites will be seen on the skin scrape, even when the cat has the disease. The mites seem to be present in lower numbers in cats than in dogs, so the disease is easier to miss. It is also more difficult to determine in the case of a positive scrape, as these can be normal mites in the skin.

Feet and faces are difficult to scrape, so plucking the hair from these areas is sometimes tried in the hope of dislodging mites from the hair follicle. Occasionally, skin biopsies are also used to locate the mites. During subsequent visits, the assessment of response to therapy relies on a negative skin scrape, so scrapes are routinely repeated at the same sites monthly when monitoring cases with demodicosis.

Feline demodectic treatment

Treatment for cats is not described as well as for dogs, because the disease is so much less common in felines. It has been reported that a lime sulfur bath every week is usually curative in four to six weeks. Amitraz, which is very effective in dogs with mites, should not be used in cats. It is not FDA-approved and the side effects of this medication can be serious, even resulting in death of the affected cat.

 

 

 

References
Payne, P.A., Dryden, M.W., Carter,G.R. External Parasitic Diseases of Dogs and Cats. In: A Concise Guide to Infectious and Parasitic Diseases of Dogs and Cats International Veterinary Information Service, Ithaca NY. www.ivis.org
Tilley, L.P., Smith, F.W.K. The Five Minute Veterinary Consult Canine and Feline. Second Edition. Lippincott Williams & Wilkins, Baltimore, 2000.
Demodectic Mange in the Cat. www.maristvet.com