In the study reported here, the pioneer fipronil/(S)-methoprene topical product (FRONTLINE® PLUS, Merial Limited, Duluth, GA) was compared to the oral spinosad product (COMFORTIS® Elanco, Greenfield, IN) for efficacy against adult fleas and preventing egg production. The product presentations, doses and labelling were the one applicable in the USA. Using a standard protocol, 200 cat fleas of mixed sex were applied to dogs on Days 1, 7, 14, 21, 28, 35, and 42. Dogs were combed to remove fleas 24 hours post-infestation, the fleas were counted, collected, and then reapplied to each dog following completion of their respective count. At 48 hours post-infestation, comb counts were performed and fleas were removed. No fleas were collected from any dog in the fipronil/(S)-methoprene group at any 24 or 48 hours post-infestation assessment throughout the six weeks study, yielding a preventive efficacy of 100%. For the spinosad treatment, efficacy was 100% at 24 hours and 48 hours through Day 16, and thereafter declined. The results observed in the spinosad-treated dogs were highly variable between animals. At the 24 and 48 hours counts following the Day 21 infestation, only five of eight spinosad-treated dogs (62.5%) were flea-free. Following the Day 28 infestation, spinosad efficacy fell to 85% and 89%, for the 24 hours and 48 hours counts, and only two dogs (25%) were flea free, compared to 100% flea-free dogs in the fipronil/(S)-methoprene group. No fleas were collected from the fipronil/(S)- methoprene treated dogs throughout the entire study, therefore, no eggs were collected at any time from any dog in the group. However, in the spinosad group adult fleas were found on dogs starting on Day 21 and by Day 30, 42 eggs were collected from one dog that had 107 adult fleas counted at 48 hours. At Day 37 and Day 49, more than 100 eggs were collected from each dog in the spinosad-treated and control groups.

BackgroundCat fleas, Ctenocephalides felis, are one of the most common ectoparasites infesting dogs and their environments. This study evaluated the efficacy of imidacloprid + pyriproxyfen (PPF) (Advantage® II for Dogs) and spinosad (Comfortis®) against established C. felis populations in dogs’ simulated home environments.MethodsThirty Beagle dogs were randomly assigned to three groups of 10 dogs each and treated twice (Study Days 0 and 28) with imidacloprid + PPF, spinosad tablets, or a negative control (untreated). Dogs were housed individually in controlled simulated home environments capable of supporting the flea life cycle. Flea infestations were established in these environments by infesting each dog with 100 adult cat fleas on Study Days −21, -16 and 1. The impact of the treatments on fleas in the dogs’ environments were assessed by collecting floor mat samples from each simulated home environment, incubating them for 32 days, and counting the number of emerging adult fleas. On Study Days 7, 14, 21, 28, 35, 42, 49 and 56, after collection of the cocoa matting samples, each dog was infested with an additional 5 ± 1 fleas to maintain the environmental infestations. Flea comb counts on dogs were conducted on Study Days 0 (pretreatment) and 63.ResultsFrom Study Days 7–28, flea infestations in the imidacloprid + PPF environments were significantly lower (p < 0.03) than those in the spinosad environments. Following the second treatment, flea infestations in all the imidacloprid + PPF environments fell to zero for the remainder of the study. In contrast, flea infestations persisted in some of the spinosad environments through the study’s end.On Study Day 63 all 10 dogs treated with imidacloprid + PPF were flea free, while only one of the 10 spinosad treated dogs was flea free. Flea counts on the other 9 spinosad treated dogs ranged from 3 to 46 fleas/dog (geometric mean = 8.6). A mean of 405 adult fleas/animal were recovered from the control dogs on Study Day 63.ConclusionFlea infestations in environments of dogs treated with imidacloprid + PPF declined more rapidly than in those containing dogs treated with spinosad. Flea infestations were completely eliminated by Study Day 56 in environments of dogs treated with imidacloprid + PPF, but persisted through the study’s end in some of environments of dogs treated with spinosad.