Generalized Demodicosis in a Golden Retriever

Adult-onset generalized demodicosis on the forelimb of the patient

Paris, a 13-year-old neutered golden retriever, presented with several areas of alopecia, erythema, scaling, and crusting on the forelimbs, posterior region, and hindlimbs with pruritus. Deep skin scrape detected numerous adult and immature Demodex canis mites, and superficial skin cytology revealed numerous cocci and some degenerate neutrophils. The dog was diagnosed with adult-onset generalized demodicosis and superficial pyoderma and prescribed cephalexin (27 mg/kg twice a day) and weekly baths with 3% chlorhexidine shampoo. Testing was negative for the ABCB1-1Δ  gene defect (MDR1 mutation), and ivermectin was initiated at 50 µg/kg PO once a day and doubled every 3 days to reach 400 µg/kg once a day. Two days after the high dose was reached, the dog developed head tremors and mydriasis and appeared moderately depressed; ivermectin was stopped and neurologic signs disappeared. The dog was referred to a dermatologist for management of demodicosis. Skin scrape from lesional skin revealed numerous D canis mites. Skin cytology showed pyoderma was controlled. Cephalexin and weekly bathing were maintained for 3 weeks and gabapentin initiated at 10 mg/kg twice a day for management of pain from chronic osteoarthritis.