Comparison of efficacy, safety, and convenience of selamectin versus ivermectin for treatment of Trixacarus caviae mange in pet guinea pigs (Cavia porcellus).

OBJECTIVE: To determine the efficacy and safety of topical administration of selamectin and to compare selamectin treatment with a common ivermectin protocol for the treatment of natural infestation with Trixacarus caviae in pet guinea pigs.
DESIGN: Clinical trial. ANIMALS: 17 mixed-breed pet guinea pigs with active mite infestation. PROCEDURES: Guinea pigs were randomly allocated to receive a single dose of selamectin topically (15 mg/kg [6.8 mg/lb]) or ivermectin (400 μg/kg [181.8 μg/lb], SC) every 10 days for 4 injections. Microscopic examination of skin scrapings from all animals was performed at 10-day intervals for 60 days, and the presence of mites or mite eggs was recorded. The efficacies of the 2 treatment protocols were compared at every time point.
RESULTS: Pruritus resolved by day 10 in all animals. Animals were microscopically mite-free on days 30 and 40 in the selamectin and ivermectin treatment groups, respectively, but groups did not differ significantly in regard to the number of mite-positive animals at any timepoint. Recurrence of infection was not noted in either treatment group. No adverse reactions were observed in any of the treated animals. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a single topical application of selamectin at a dose of 15 mg/kg or repeated SC injection of ivermectin at a dose of 400 μg/kg can eliminate T caviae mites from guinea pigs within 30 and 40 days, respectively. Although effectiveness did not significantly differ between the 2 treatments, the convenience associated with the single topical dose of selamectin made it a preferable treatment modality for both patients and owners.