Determination of anthelmintic efficacy against equine cyathostomins and P arascaris equorum in F rance

Summary This article reports the results of a faecal egg count reduction test on 4 farms in F rance, as an integrated part of the routine deworming strategy against horse cyathostomins and P arascaris equorum . Treatment with fenbendazole ( FBZ ) or ivermectin ( IVM ) was evaluated in yearlings on F arms 1 and 2 and treatment with pyrantel embonate ( PYR ) was tested on F arms 3 and 4. Calculation of the arithmetic mean faecal egg count reduction and the 95% confidence intervals (95% CI ) around the mean was performed using bootstrap analysis. For equine cyathostomins, resistance to FBZ was found with an arithmetic mean reduction of 48.8% (95% CI : 1.9–69.3%). On F arms 1 and 2, horses with reduced efficacy were identified. PYR was found to be effective against cyathostomins, with an arithmetic mean reduction of 95.3% (95% CI : 84.6–99.8%), as well as IVM (100%). For P . equorum , both FBZ and PYR were effective (100% reduction). The efficacy of IVM , however, was low (45.5%; 95% CI : 0–96.3%). These results confirm that FBZ resistance in equine cyathostomins is present in F rance and that anthelmintic resistance to IVM is present in P . equorum . This study underlines the necessity to evaluate the efficacy of horse deworming strategies on a regular basis under field conditions.