By: Katherine Irwin, DVM, ACVD
Gulf Coast Veterinary Specialists, www.mygcvs.com
With regards to skin a common reason cats are taken to their veterinarian is because they are developing bald patches. A term used to refer to balding or hair loss is “alopecia.” Sometimes the alopecia is paired with the observation of excessive grooming, but in other instances the overgrooming may not be so obvious. In fact, cats can be quite subtle in their grooming behavior, making it difficult to appreciate the cat is causing the hair loss. But, in the majority of cases, the alopecia is indeed a result of the cat overgrooming versus the hair falling out and/or failing to regrow on its own. This is further supported by the observation that the sites often affected include the belly, inside and back of thighs, forelegs, and sometimes the flanks and armpits – areas where the cat can easily lick.
Self-induced alopecia can be the result of medical conditions that result in itch or discomfort, as well as from behavioral conditions that can be a result of environmental and social stressors that result in displacement overgrooming behavior. When the hair loss is a result of overgrooming due to a behavioral cause it is termed “psychogenic alopecia.” Because the newly exposed skin can often be non-inflamed appearing in cats with self-induced alopecia, it is tempting to assume the overgrooming is behavioral or psychogenic in origin. However, with a methodical diagnostic work-up the majority of cats with self-induced alopecia ultimately are diagnosed with a medical condition versus a solely behavioral or psychogenic disorder. Thus, a diagnosis of psychogenic alopecia should truly be one of exclusion where other potential diagnoses have been first ruled out. Simply defaulting to a diagnosis of psychogenic alopecia will likely result in further frustration as the cat’s alopecia will unlikely improve with treatment solely directed at a behavioral disorder.
Medical conditions that can lead to self-induced alopecia include allergies (flea allergy, food allergy, and environment/ pollen allergies), ectoparasites (fleas and mites), ringworm infections, and occasionally systemic illnesses that lead to discomfort or pain, such as urinary tract infections. Given the high incidence of flea allergy, all cats with skin disease, as well as their canine and feline housemates, should be maintained on monthly year-round flea prevention. This is especially true in Houston, given this region’s high flea burden. To assess for a food allergy, which can be a common cause of overgrooming in cats, an 8-10 week, very strict, limited, novel ingredient diet trial should be pursued. A ringworm (DTM) culture will help determine if the cat has a ringworm infection. Multiple skin scrapes should also be performed to look for mites. One species of mite of particular importance, as it is relatively common in the Gulf Coast region, is Demodex gatoi. The classic presentation for infestation with this mite is the cat with self-induced alopecia where the exposed skin is otherwise noninflamed appearing. This mite can be very difficult to find on skin scrapes thus a negative skin scraping does not rule it out. Instead, if the cat’s history and physical exam are at all supportive of infestation with this mite, a treatment trial must be performed.
Because this mite can be communicable between cats (although not all infested cats will show symptoms) housemates must also be treated and the cat kept strictly indoors during the treatment period. Blood work (complete blood count, chemistry panel, +/- thyroid levels) and urine analysis may need to be considered to assess for systemic diseases. And, on occasion, skin biopsies may also be advised. If the above tests and diagnostic trials are negative or do not lead to resolution of the overgrooming, yet the cat improves with steroid therapy, a diagnosis of environmental allergies becomes most likely. However, if the same cat does not improve with steroid therapy then a diagnosis of psychogenic alopecia can be made.