A series of randomized, controlled, masked field studies was conducted to assess the efficacy and safety of
selamectin in the treatment of
flea infestations on dogs and cats, and in the prevention of heartworm
infection in dogs. In addition, observations were made on the beneficial effect of
selamectin treatment on dogs and cats showing signs of flea
allergy dermatitis (
FAD). In all studies
selamectin was applied topically, once per month, in unit doses providing a minimum dosage of 6mgkg(-1). Dogs and cats with naturally occurring
flea infestations, some of which also had signs associated with
FAD, were assigned randomly to receive three months of topical treatment with
selamectin (220 dogs, 189 cats) or a positive-control product (dogs:
fenthion, n=81; cats:
pyrethrins, n=66).
Selamectin was administered on days 0, 30, and 60. Day 0 was defined as the day that the animal first received treatment. Flea burdens were assessed by flea comb counts and clinical evaluations 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-treated dogs were reduced by 81.5, 86.8, and 86.1%, respectively, compared with day 0 counts. Also, on days 30, 60, and 90, mean flea counts in
selamectin-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%, respectively, compared with day 0 counts.
Selamectin also was beneficial in alleviating signs in dogs and cats diagnosed clinically with
FAD. A total of 397 dogs free of adult heartworm
infection from four heartworm-endemic areas of the USA were allocated randomly to six months of treatment with
selamectin (n=298) or
ivermectin (n=99).
Selamectin achieved a heartworm prevention rate of 100%, with all dogs testing negative for microfilariae and adult heartworm
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 doses). 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
flea infestations in dogs and cats without the need for simultaneous treatment of the environment or of in-contact animals and also was beneficial in alleviating signs associated with
FAD.
Selamectin also was 100% effective in preventing the development of canine heartworms and was safe for topical use in dogs and cats.