Which organism is a hair follicle mite commonly associated with patchy hair loss in dogs?

• A. Sarcoptes scabiei
• B. Demodex
• C. Otodectes cynotis
• D. Cheyletiella yasguri

Answer: (B)

Demodex mites live and reproduce in hair follicles and associated sebaceous glands. When they proliferate, especially in young dogs or those with some immune impairment, they cause demodicosis, which commonly presents as patchy hair loss with localized areas of alopecia on the face and front legs. This follicle-centered habitat explains why patchy alopecia is a hallmark presentation.

In contrast, Sarcoptes scabiei is a surface-dwelling mite that causes intense itching and more generalized crusting and hair loss; Otodectes cynotis targets the ear canal and causes ear itching and discharge; Cheyletiella yasguri causes walking dandruff with scaling on the surface of the skin. These patterns are not the characteristic follicle-centered cause of patchy hair loss, making Demodex the best fit for this presentation.