Efficacy and safety of selamectin against fleas and heartworms in dogs andcats presented as veterinary patients in North America

A series of randomized, controlled, masked field studies was conducted to a sc;ess the efficacy and safety of selamectin in the treatment of flea infes tations on dogs and cats, and in the prevention of heartworm infection in d ogs. In addition, observations were made on the beneficial effect of selame ctin treatment on dogs and cats showing signs of flea allergy dermatitis (F AD). In all studies selamectin was applied topically, once per month, in un it doses providing a minimum dosage of 6 mg kg(-1). Dogs and cats with natu rally occurring flea infestations, some of which also had signs associated with FAD, were assigned randomly to receive three months of topical treatme nt with selamectin (220 dogs, 189 cats) or a positive-control product(dogs: fenthion, n=81; cats: pyrethrins, n=66). Selamectin was administered on da ys 0, 30, and 60. Day 0 was defined as the day that the animal first receiv ed treatment. Flea burdens were assessed by flea comb counts and clinical e valuations of FAD were performed before treatment, and on days 14, 30, 60, and 90. On days 30, 60, and 90, mean flea counts in selamectin-treated dogs were reduced by 92.1, 99.0, and 99.8%, and mean flea counts in fenthion-tr eated dogs were reduced by 81.5, 86.8, and 86.1%, respectively, compared wi th day 0 counts. Also, on days 30, 60, and 90, mean flea counts in selamect in-treated cats were reduced by 92.5, 98.3, and 99.3%, and mean flea counts in pyrethrin-treated cats were reduced by 66.4, 73.9, and 81.3%, respectiv ely, compared with day 0 counts, Selamectin also was beneficial in alleviat ing signs in dogs and cats diagnosed clinically with FAD. A total of 397 do gs free of adult heartworm infection from four heartworm-endemic areas of t he USA were allocated randomly to six months of treatment with selamectin ( n=298) or ivermectin (n=99). Selamectin achieved a heartworm prevention rat e of 100%, with all dogs testing negative for microfilariae and adult heart worm antigen on days 180 and 300. Selamectin was administered to a total of 673 dogs and 347 cats having an age range of 6 weeks to 19 years (3954 dos es). The animals included 19 purebred or crossbred Collies (Bearded, Border , and unspecified). There were no serious adverse events. Results of these studies indicated that selamectin was highly effective in the control of fl ea infestations in dogs and cats without the need for simultaneous treatmen t of the environment or of in-contact animals and also was beneficial in al leviating signs associated with FAD. Selamectin also was 100% effective in preventing the development of canine heartworms and was safe for topical us e in dogs and cats. (C) 2000 Elsevier Science B.V. All rights reserved.