Efficacy of topical administration of prallethrin-permethrin-piperonyl butoxide (Bronco® Equine Fly Spray) for the treatment and control of flies and other nuisance insects of horses.

Abstract

Abstract Numerous biting and nuisance insects are a noted cause of discomfort and stress to horses. Pyrethrins and pyrethroids have been used for many years in numerous formulations for the control of insect pests in animals, humans and in the environment. There are, however, few studies reporting their field efficacy in horses. The aim of the present study was to evaluate the repellent activity of a spray formulation based on prallethrin and permethrin synergized with piperonyl butoxide (BRONCO® Equine Fly Spray, Farnam Companies, Inc., USA) against annoying and harmful insects for horses in field conditions. Nine horses of mixed breed were divided into 2 groups (treatment and control). Pre-treatment insect counts were compared to daily counts for 4 days post-treatment (pt). One minute after the administration of the product (Day 0), all the horses were negative for the presence of insects. All counts up to the 6-hour pt check remained negative for H. equina, tabanid flies and Simulium spp., showing 100% efficacy. This remained above 90% throughout the study. For the H. equina the repellent efficacy remained > 99.7% for all 4 days pt, for tabanid flies > 93.3% and for Simulium spp. > 97.4%. The efficacy against Musca spp. decreased from 82.2% at Day 0 to 62.2% at Day 3. Treatment was well tolerated. In conclusion, despite the low number of tested horses, Bronco® has demonstrated high insecticide and repellent efficacy and a good persistence, maintained for up to 4 days post treatment, against the most common species of insects harmful for horses.