Ivermectin for treatment of generalized demodicosis in dogs.

OBJECTIVE To evaluate the efficacy of daily administration of ivermectin in the treatment of dogs with amitraz-resistant generalized demodicosis. DESIGN Prospective, clinical trial. ANIMALS Twelve privately owned dogs with juvenile-onset or adult-onset generalized demodicosis that had failed to respond to biweekly or weekly applications of 0.025% amitraz solution. PROCEDURE All dogs were treated with undiluted ivermectin at a dosage of 0.6 mg/kg of body weight, PO, every 24 hours. There was no other parasiticidal agent given topically or systemically. A physical examination and multiple skin scrapings were performed every 2 to 4 weeks while dogs were receiving ivermectin. Skin scrapings were performed at approximately the same sites at every examination. After no mites were seen, treatment was continued for at least 2 more weeks and then stopped. Dogs were reexamined, and skin scrapings were repeated if any skin lesions developed. For dogs that remained clinically normal, follow-up information was obtained by telephone. Dogs that were free of clinical signs of demodicosis 12 months after ivermectin administration was discontinued were considered cured. RESULTS Ten of 12 dogs were cured. Median duration of treatment for these dogs was 10 weeks (range, 6 weeks to 5 months). Two dogs were failures, relapsing 10 months and 11.5 months after treatment was stopped. One of these dogs was successfully treated with a second course of ivermectin. Mild ivermectin toxicosis developed in 1 dog after 6 weeks of treatment; side effects resolved shortly after the treatment was stopped. CLINICAL IMPLICATIONS Daily use of ivermectin, at a dosage of 0.6 mg/kg, PO, was found to be effective in the treatment of generalized demodicosis in dogs.