Prevalence of Demodex canis-positive healthy dogs at trichoscopic examination

Demodex canis is thought to be present in small numbers in the skin of most healthy dogs; however, available data on the prevalence of normal dogs harbouring D. canis are scarce. The purpose of this study was to investigate, using microscopic examination of plucked hairs, the prevalence of healthy dogs harbouring D. canis. Seventy-eight clinically healthy dogs with no history of dermatological problems and clinically normal skin and hair coat were included in the study. Five areas (perioral skin 2-3mm from both labial commissures, periungual skin of the third digit of both anterior paws and chin) were examined in each dog. Fifty to sixty hairs were plucked from each skin site and microscopically examined. No D. canis mites were observed and only one adult form of Demodex injai was found in the labial commissure of one dog. Based on these results, the estimated prevalence of healthy dogs harbouring D. canis in clinically normal skin should not exceed the threshold of 5.4%, with 95% confidence level. Considering our and previous findings, we propose that, although small numbers of D. canis might inhabit the skin of normal dogs, the probability of finding these mites in normal dogs is low. Consequently, in most cases, the presence of a D. canis mite in the skin should not be considered as indicative of normality.