Treatment efficacy of pyrantel, fenbendazole and macrocyclic lactones in equine strongyles in Germany using FECRT and the model eggCounts.
Authors: Döberl J, Li Z, Furrer R, Jäger M C
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Anthelmintic Efficacy Against Equine Strongyles in Germany Reduced efficacy of antiparasitic drugs against small strongyles is well documented but current field data remains limited; this German study addresses that gap by evaluating 1913 deworming treatments across 1670 horses using both faecal egg count reduction testing (FECRT) and the statistical model eggCounts. Pyrantel, the most commonly used compound in the study (1682 treatments), demonstrated concerning results: only 68.7% achieved the gold-standard >95% faecal egg count reduction, and was classified as 'low resistant' by both analytical methods (FECRT: 89.5–91.1%, eggCounts: 88.1–88.7%). Fenbendazole performed significantly worse, with just 21.4% of treatments effective and classification as 'resistant' (FECRT: 49.1–65%, eggCounts: 42.9–50.4%), whilst macrocyclic lactones remained highly effective at 98.1% of treatments achieving >95% reduction. The authors recommend continuing pyrantel use given that nearly 70% of treatments remained efficacious, but crucially advocate implementing post-treatment faecal egg count checks 10–14 days after administration as standard practice—a pragmatic shift that would allow practitioners to identify failing treatments promptly and adjust protocols before clinical disease develops or resistance becomes entrenched in individual yards.
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Practical Takeaways
- •Pyrantel remains a viable first-line treatment for strongyles in most cases, but nearly one-third of treatments show inadequate efficacy—routine fecal egg count testing 10-14 days post-treatment is now essential practice
- •Fenbendazole should be avoided or used with extreme caution due to widespread resistance; consider macrocyclic lactones as primary alternative when pyrantel fails
- •Implement post-treatment efficacy monitoring (FECRT) as standard protocol rather than assuming treatment success; this directly impacts parasite control programs and reduces selection pressure for further resistance
Key Findings
- •Pyrantel showed reduced efficacy in 31.3% of treatments, classified as 'low resistant' with FECR of 89.5-91.1% by FECRT
- •Fenbendazole demonstrated insufficient efficacy in the majority of treatments, classified as 'resistant' with FECR of 49.1-65.0%
- •Macrocyclic lactones remained highly effective with 98.1% of treatments achieving FECR >95%, classified as 'susceptible' to 'low resistant'
- •Of 1913 total dewormings analyzed, 1682 used pyrantel, 56 used fenbendazole, and 162 used macrocyclic lactones across German equine population