Factors affecting the frequency of ear canal and face infestation by Otodectes cynotis in the cat

Otodectes cynotis is responsible for at least 50% of canker cases diagnosed in cats world-wide. The role of Demodex cati in the pathogenesis of otitis and acne is still obscure. The aims of this study were to estimate the prevalence of O. cynoyis and D. cati infestations in clinically normal cats in northern Greece, to determine the factors that are associated with the probability and severity of infestation in the cat, and to examine the importance of these mites in the pathogenesis of feline acne. Samples from 161 cats were examined by flushing the ear canals and by taking skin scrapings of the chin and lip area. The results were combined with various factors (sex, age, living style, hair coat type and presence of pruritus, of ear discharge, of acne-like lesions) in order to carry out a risk analysis. Two separate logistic regression analyses were performed. One, on the infestation/non-infestation potential with O. cynotis and the other, on the degree of such infestation as mild-to-moderate (< or =5 mites/field) or severe (>5 mites/field). D. cati was not detected in any of the 161 cats. The prevalence of O. cynotis was estimated at 25.5% (95% confidence interval (CI) 19-32). The rate of mite infestation was higher with the presence of ear discharge (odds ratio 9, 95% CI 3.3-24.5), periaural pruritus (odds ratio 3.6, 95% CI 1.8-8) and acne-like lesions (odds ratio 3.3, 95% CI 1.2-9). Cats with mild-to-moderate degree of infestation had 18 times higher chance of exhibiting an ear discharge than those with a severe infestation. The log-odds of mild-to-moderate parasitism were linearly related to the age.