Efficacy of selamectin against adult flea infestations (Ctenocephalides felis felis and Ctenocephalides canis) on dogs and cats

Selamectin was evaluated in eight controlled studies (4 in dogs, 4 in cats) to determine the efficacy of a single topical unit dose providing the reco mmended minimum dosage of 6 mg kg(-1) against Ctenocephalides felis felis a nd Ctenocephalides canis fleas on dogs and against C. felis on cats. In add ition, the effect of bathing on the efficacy of selamectin against C. felis was evaluated. Identical studies were performed in Beagles and domestic sh orthaired cats. For each study, animals were allocated randomly to treatmen ts of 8-12 animals each. All studies (dog studies A, B, C, and D and cat st udies A, B, C, and D) evaluated the efficacy of selamectin with;out bathing . In addition, study C in both dogs and cats evaluated efficacy with a sham poo bath at 24 h after dosing, and study D evaluated the efficacy of selame ctin with water soaking at 2 h after dosing or with a shampoo bath at 2-6 h after dosing. Dog study B evaluated efficacy against C. canis, whereas all other studies used C. felis. In each study, selamectin was administered on day 0 as a topical dose that was applied directly to the skin in a single spot at the base of the neck in front of the scapulae. Dogs and cats were i nfested with approximately 100 viable unfed C. felis or C. canis on days 4, 11, 18, and 27. On days 7, 14, 21, and 30, approximately 72 h after infest ation, a comb count of the number of viable fleas present on each animal wa s made. For C. felis and C. canis for dogs and cats, compared with controls , selamectin achieved significant reductions in geometric mean adult flea c omb counts of greater than or equal to 98.9% on days 7, 14, and 21 in all e ight studies. On day 30, die reduction for C. felis remained at or above 98 .0%. This included the dogs and cats that were soaked with water or bathed with shampoo at 2, 6, or 24 h after treatment. There were no significant (P >0.05) differences between the flea counts from selamectin-treated animals in these studies, regardless of bathing status. On day 30, a significant re duction of 91.8% was achieved against C, canis on dogs. Thus, these studies demonstrated that a single topical unit dose of selamectin was highly effe ctive against adult fleas on dogs and cats for at least 27 days. (C) 2000 E lsevier Science B.V. All rights reserved.