Determination of anthelmintic efficacy against equine cyathostomins and Parascaris equorum in France

Abstract

Summary This article reports the results of a faecal egg count reduction test on 4 farms in France, as an integrated part of the routine deworming strategy against horse cyathostomins and Parascaris equorum. Treatment with fenbendazole (FBZ) or ivermectin (IVM) was evaluated in yearlings on Farms 1 and 2 and treatment with pyrantel embonate (PYR) was tested on Farms 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 Farms 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 France 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.

The role of density-dependent arrested larval stages on parasite dynamics and stability: Lessons from nematodes and donkeys

“…The main supposed reason of the ineffectiveness of treatments is the development of anthelmintic resistance in strongyle populations or the low exposure of mucosal larvae to many anthelmintic drugs (Love, 2003;Corning, 2009;Lyons et al, 2011a;Geurden et al, 2013). The belief that anthelmintic treatments are often ineffective in controlling strongyle infections due to a low exposure of mucosal larvae is not confirmed by our results, since mucosal larvae additional mortality of 80% changes only slightly the output of the models Fig.…”

Evidence‐based considerations for control of Parascaris spp. infections in horses

“…Some studies have reported good efficacy of fenbendazole against ascarid populations that were resistant to ivermectin (Hearn and Peregrine ; Geurden et al . ). Thus, the situation for the benzimidazoles is similar to that of the pyrantel salts.…”

“…Signs of fenbendazole resistance have been reported in single studies from the USA (Lyons et al 2008) and Australia (Armstrong et al 2014). Some studies have reported good efficacy of fenbendazole against ascarid populations that were resistant to ivermectin (Hearn and Peregrine 2003;Geurden et al 2013). Thus, the situation for the benzimidazoles is similar to that of the pyrantel salts.…”

Anthelmintic resistance and novel control options in equine gastrointestinal nematodes

“…Anthelmintic resistance (AR) is generally defined as ‘when a previously effective drug is unable to kill the parasite population while exposed to therapeutic doses (Jabbar et al ., 2006) or loss of sensitivity to a drug in parasitic population that was sensitive to the same drug which is thought to be genetically transmitted (Kohler, 2001)’. AR has been documented in parasites of different animal species including cattle (Lifschitz et al ., 2010; Geurden et al ., 2015), sheep and goats (Coles, 2005; Domke et al ., 2012) and horses (Geurden et al ., 2013; Wolf et al ., 2014; Saes et al ., 2016).…”