Authors: Jürgenschellert Laura, Krücken Jürgen, Bousquet Eric, Bartz Jürgen, Heyer Nina, Nielsen Martin K, von Samson-Himmelstjerna Georg
Journal: Frontiers in veterinary science
Summary
# Editorial Summary German researchers screened 484 horses across 48 farms using faecal analysis and molecular diagnostics to establish current prevalence of large strongyles (Strongylus spp.), parasites historically controlled through routine anthelmintic programmes but potentially re-emerging as a concern. Whilst direct detection methods identified S. vulgaris in only 1.3% and S. edentatus in 6.3% of positive samples using PCR, serology against larval antigens painted a strikingly different picture, with 21.2% of individual horses and 83.3% of farms showing antibody positivity—indicating substantially higher exposure to these parasites than conventional faecal testing suggests. Younger horses with increased pasture access carried greater infection risk, and critically, horses managed under selective deworming protocols showed 4.4 times higher odds of S. vulgaris seropositivity compared to those treated four times yearly, whilst no benzimidazole resistance mutations were detected in the samples examined. These findings imply that current diagnostic thresholds may underestimate disease burden and that strategic anthelmintic regimens—particularly selective treatment approaches—may be insufficient to prevent larval exposure and immune sensitisation, even if mature worm burdens remain suppressed. For practitioners, this suggests the need for reconsideration of deworming strategies in young stock and heavily grazed animals, alongside awareness that serological evidence of exposure may warrant intervention despite negative faecal results.
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Practical Takeaways
- •Serological testing reveals S. vulgaris exposure is much more common than faecal egg counts suggest—horses under selective treatment protocols may be at significantly higher risk despite lower egg shedding, warranting reconsideration of treatment intervals
- •Young horses with high pasture access are highest-risk groups; consider targeted strategic treatments for these demographics rather than blanket protocols
- •Current anthelmintic resistance to benzimidazoles is not yet detected in German strongyles, but continued surveillance is essential as resistance patterns evolve
Key Findings
- •Strongyle eggs detected in 66.7% of horses; S. vulgaris and S. edentatus confirmed by PCR in only 1.3% and 6.3% of samples respectively, but serology detected S. vulgaris exposure in 21.2% of individual horses (83.3% farm-level prevalence)
- •Selective treatment protocol resulted in 4.4-fold higher odds of S. vulgaris seropositivity compared to four-times-yearly treatment
- •Young age and increased pasture access were significant risk factors for strongyle egg shedding and S. vulgaris exposure
- •No benzimidazole resistance-associated β-tubulin polymorphisms detected in S. vulgaris samples, suggesting resistance mechanisms are not yet established in this population