Veterinary Technician National Exam (VTNE) Practice Exam

The focal area of alopecia accompanied by comedones in a 6-month-old mixed breed dog is most indicative of demodecosis. Demodecosis, often caused by the Demodex mite, is characterized by localized hair loss and the presence of comedones, which are plugged hair follicles. The immune system of younger dogs, particularly those under one year old, may not be fully developed, making them more susceptible to this condition.

In this case, the dog is exhibiting a classic presentation which aligns with localized demodicosis, as these signs typically appear alongside the presence of the mites, which can lead to secondary infections if left untreated.

Other conditions, such as cheyletiellosis, sarcoptic mange, or dermatophytosis, present with different clinical signs. Cheyletiellosis often involves generalized scaling and itching, while sarcoptic mange is marked by intense pruritus and often more widespread skin lesions. Dermatophytosis usually presents with circular patches of hair loss but does not typically feature comedones. Thus, considering the specific symptoms described, demodecosis is the most plausible diagnosis.