Comparative efficacy on dogs of a single topical treatment with the pioneer fipronil/(S)-methoprene and an oral treatment with spinosad againstCtenocephalides felis

Abstract

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.

Systemic insecticides used in dogs: potential candidates for phlebotomine vector control?

“…At the oral dose of 0.75 mg/kg BW, the study reported no adverse effect in the 118 dogs treated, and 95% efficacy at controlling fleas infestations . Studies of rodents fed on diets with imidacloprid concentrations of 250 mg/kg reported sand fly mortality after blood fed on treated rodents > 85% for at least 3 days post‐treatment . One of these studies also followed larvae development and reported mortality > 90% for all larvae stages .…”

Efficacy of selamectin, spinosad, and spinosad/milbemycin oxime against the KS1 Ctenocephalides felis flea strain infesting dogs

“…In a study evaluating and comparing the spinosad and spinosad/milbemycin oxime tablet formulations administered to dogs, both formulations provided 100% efficacy 48 hours after the Day 28 flea infestation [14]. However, in a different study, the efficacy of spinosad administered to dogs 24 and 48 hours after the Day 28 infestation was 85.0% and 89.0%, respectively [19]. These data are further contrasted with two previous studies evaluating the efficacy of spinosad using the KS1 flea strain where the efficacy 24 hours after the Day 28 infestation was only 22.1% and 32.5% [12].…”

Fleas infesting pets in the era of emerging extra-intestinal nematodes

“…(i.e. 100% at 24 hours during three weeks, then decreasing until 85% and 80.4% at Day 28 and Day 43 respectively) [121-124]. Spinosad, moreover, is effective in reducing flea egg production (>99.8% for about 1 month) although its absence in the skin debris of treated dogs results in no effects on environmental flea stages [121].…”

“…Larvicidal effects of imidacloprid is of practical significance in both breaking the flea life cycle and reducing the level of flea infestation in the domestic environment, spinosad and selamectin reduce egg production, and the latter has ovicidal effects impairing larval emergence [106,111,112,121]. Given that most insecticides may suffer from decreasing levels of killing speed throughout the month following administration [105,106,123,124], environmental control is mandatory. This is even more important if one considers that rapid and voracious blood sucking by adult fleas (e.g.…”