Efficacy of 65% permethrin applied as a topical spot-on against walking dandruff caused by the mite, Cheyletiella yasguri in dogs.

The efficacy of a 65% permethrin topically applied spot-on formulation (Defend EXspot Topical Remedy for Dogs, Schering-Plough Animal Health, Union, NJ) was determined against the dog mite, Cheyletiella yasguri (Smiley, 1965). Female dogs and their litters comprised the experimental unit, and all dogs in an experimental unit were treated on the same day 4 to 6 weeks after whelping. Mites and mite eggs were counted weekly on an untreated control group of six litters (15 pups) and on a group of six litters (14 pups) treated with 65% permethrin. Pups in the untreated control group maintained high numbers of Cheyletiella yasguri throughout the 14- to 21-day observation period. No mites or mite eggs were detected on dogs within 7 to 21 days after application of 65% permethrin. No adverse reactions were noted during the study. Clinical signs of infestation with C. yasguri--which included skin irritation, thickening of the stratum corneum, scratching with resultant scabs, pruritus, and flaky, scaly skin-were eliminated when mites were killed by the 65% permethrin formulation.