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Another itchy cat, now what (Proceedings)

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Nov 01, 2010

The most common derm problem in cats is itchy skin disease. Often these cats have allergic skin disease with many cases related to flea allergy dermatitis, atopic dermatitis and adverse food reactions. Though uncommon in most parts of the world Demodex gatoi should always be considered as well as the role of psychogenic contributions to the dermatitis. However it is also important to recognize the role pyoderma and Malasseizia sp. play in pruritic cats, to be discussed in the session, Feline infectious skin disease, more than you realized. If lesions other than barbered alopecia are present then skin cytology is the first thing to do. If infection is present then appropriate antimicrobial therapy is indicated. Once these aspects have been dealt with then it is likely that allergic disease, food allergy or atopic dermatitis is present and lifelong management will be needed.

Demodex gatoi

Compared to Demodex cati this mite is shorter in length with a broad based blunted abdominal segment. This mite is a surface dweller in contrast to the normal follicular orientation of classic demodex from D. cati or canis. It also appears to be somewhat contagious as outbreaks have been described. Clinically there may be minimal disease and pruritus or intense pruritus. Pruritus is the main symptom though scale may also occur. Hair loss due to excessive grooming occurs and may involve the abdomen, forelegs (especially elbows), head and neck or rear legs. As such it mimics allergic disease or psychogenic dermatitis. In cats that are excessively grooming mites may be more difficult to find though in mildly affected non-pruritic cats they are usually present in abundant numbers. Scraping other normal or mildly affected cats in a household may lead to a diagnosis. Individual itchy cats have anectdotally been diagnosed with fecal flotation. Therapy has been successful with lym dyp as well as ivermectin 1mg/4-5kg eod.

Psychogenic dermatitis

In the past many cats were diagnosed as psychogenic dermatitis and in one study in France of 783 feline derm cases seen in 1992-1997 psychogenic alopecia was diagnosed in 4.7%. This is compared to the diagnosis of flea bite hypersensitivity 42.9%, food allergy 25.2% and atopy 22.4%. In recent years most dermatologist feel psychogenic dermatosis as the primary cause of hairloss and excessive grooming is rare. A study of 21 cats that had been tentatively diagnosed with psychogenic alopecia and referred to behaviorists for that problem revealed only 2 cases actually seemed to truly be psychogenic and responsive to clomipramine therapy. This study showed limited value in histopathology for making the diagnosis. Another study evaluating histopathology in self induced alopecia cats also noted that this is not a good way to separated normal from affected cats nor to determine an etiology. The problem is that psychogenic factors are known to play a role in humans with many skin diseases, but especially atopic dermatitis. Recently this has been described in dogs as well and likely occurs in cats. There may be some cats that using behavior modification drugs such as clomipramine may improve the control of atopic dermatitis.

Flea Allergy Dermatitis

In most geographic areas, FAD is often described as a common cause of skin disease in dogs and cats. A recent survey in the United Kingdom showed in veterinary clinics a prevalence of lesions compatible with FAD as 8% in cats[9]. The advent of newer more effective flea control products has been both beneficial and detrimental to clinical practice. The new products have greatly minimized the impact of flea allergy dermatitis in many practices and allowed for much more effective flea control. At the same time many clients utilizing these products no longer believe fleas can be the cause of disease, making the client acceptance of the diagnosis more problematic.