An investigation of anthelmintic efficacy against strongyles on equine yards in Scotland.

Authors: Stratford C H, Lester H E, Pickles K J, McGorum B C, Matthews J B

Journal: Equine veterinary journal

DOI: 10.1111/evj.12079 PubMed: 23662803Log in to save

Summary

# Editorial Summary Cyathostomins remain the most economically significant equine endoparasites, yet anthelmintic resistance in these small strongyles is now widespread, leaving practitioners reliant on three existing drug classes: benzimidazoles, tetrahydropyrimidines and macrocyclic lactones. Stratford and colleagues conducted faecal egg count reduction tests (FECRT) on Scottish yards to assess real-world efficacy of these anthelmintics against cyathostomin populations, establishing baseline data on resistance patterns across different management systems and geographic locations. The findings revealed variable efficacy across all three drug classes, with some yard populations demonstrating reduced responsiveness to benzimidazoles and pyrantel in particular, highlighting the emergence of resistance to these older compounds. These results underscore the critical importance of implementing targeted, evidence-based worming strategies tailored to individual yard populations rather than blanket protocols, and emphasise the urgent need for routine FECRT monitoring to guide treatment decisions and preserve the efficacy of remaining anthelmintics until new therapeutic options become available.

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Practical Takeaways

•Anthelmintic resistance is widespread in strongyles, so efficacy testing of your chosen products is critical before implementing a yard protocol
•Understand the three available drug classes (benzimidazoles, tetrahydropyrimidines, macrocyclic lactones) and consider rotating between them to slow resistance development
•With no new anthelmintics on the horizon, rational use of current medications and targeted grazing management are essential strategies for maintaining control of cyathostomins on your yard

Key Findings

•Anthelmintic resistance in cyathostomins is common in equine populations
•Three classes of anthelmintics are currently licensed for cyathostomin control: benzimidazoles, tetrahydropyrimidines, and macrocyclic lactones
•No new anthelmintic classes are expected in the near future, necessitating evaluation of existing drug efficacy
•Field efficacy data from Scottish equine yards are essential to inform future parasite control programmes

Conditions Studied

cyathostomin infectionstrongyle infectionanthelmintic resistance

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