Monitoring equine ascarid and cyathostomin parasites: Evaluating health parameters under different treatment regimens.
Authors: Nielsen Martin K, Gee Erica K, Hansen Alyse, Waghorn Tania, Bell Julie, Leathwick Dave M
Journal: Equine veterinary journal
Summary
# Editorial Summary Growing anthelmintic resistance in equine parasites demands evidence-based alternatives to traditional intensive deworming programmes, yet guidance on minimal effective regimens remains limited. Nielsen and colleagues conducted a longitudinal field trial across four stud farms (two Standardbred, two Thoroughbred), monitoring 93 foals and 99 mares over 6–13 months under different treatment protocols: foals received either two strategic doses (2 and 5 months of age) or monthly alternating treatments, whilst mares were dewormed either twice fixed, on a threshold basis (300 strongylid eggs per gram), or every 8 weeks. Surprisingly, the minimally treated foal group (two doses) showed significantly higher ascarid and strongylid egg counts than the monthly group, yet both foal groups achieved comparable bodyweights and experienced negligible colic or diarrhoea episodes; mare groups showed no significant differences in egg counts or health outcomes regardless of treatment intensity, though fixed-schedule mares were lighter than threshold-based and bi-monthly groups. These findings suggest that while strategic two-dose programmes for foals may warrant reconsideration, threshold-based or interval deworming for mares can substantially reduce treatment frequency without compromising observable health markers—though the single-season timeframe and stud farm setting limit extrapolation to mixed-age populations and varied management systems. For practitioners, this work supports moving beyond blanket intensive protocols, particularly for adult horses, yet emphasises the continued value of monitoring faecal egg counts to guide treatment decisions and detect problematic parasite burdens before clinical signs emerge.
Read the full abstract on PubMed
Practical Takeaways
- •Consider using threshold-based deworming for mares (treating only when faecal egg counts exceed 300 epg) as an effective alternative to routine prophylactic treatments, reducing anthelmintic use and selection pressure for resistance
- •In foals, less frequent deworming (2 treatments vs. monthly) may not adequately control ascarid populations—monthly or strategic deworming may still be warranted for young stock to manage parasite burdens and development
- •Monitoring bodyweight and general health indicators alongside parasite control can help identify whether reduced treatment intensity is sustainable on your farm without negative clinical outcomes
Key Findings
- •Reduced-intensity deworming protocols (2 treatments vs. monthly) in foals resulted in no significant bodyweight differences between groups over 6 months
- •Foals receiving only 2 anthelmintic treatments (FA group) had significantly higher ascarid and strongylid egg counts than monthly-treated foals (FB group)
- •Mares dewormed on an as-needed basis (MB group, when egg counts exceeded 300 epg) showed no significant parasite burden differences compared to fixed-schedule protocols
- •Health incidents (colic and diarrhoea) were rare across all treatment groups, suggesting reduced treatment intensity did not compromise welfare over the study period