Parasites in Horses Kept in A 2.5 Year-Round Grazing System in Nordic Conditions without Supplementary Feeding.
Authors: Tydén Eva, Jansson Anna, Ringmark Sara
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Parasites in Year-Round Grazing Systems Researchers monitored endoparasite and ectoparasite burdens in 12 Gotlandsruss stallions maintained on year-round pasture in Nordic conditions for 2.5 years, treating with pyrantel when faecal egg counts exceeded 200 cyathostomin eggs per gram (EPG) to balance parasite control with conservation objectives. Monthly faecal sampling revealed seasonal patterns with cyathostomin excretion peaking during summer-autumn months and escalating year-on-year, whilst Parascaris, Oxyuris, Anoplocephala, and Gasterophilus species were detected variably throughout the study period. Notably, no correlation existed between cyathostomin EPG and body condition score, and chewing louse (Bovicola equi) infestation intensity did not correlate with increased scratching behaviour, suggesting these parasites had minimal clinical impact under this management system. Despite pyrantel being the preferred anthelmintic for biodiversity preservation, monotherapy proved insufficient at controlling cyathostomin burden; the researchers ultimately required supplementary moxidectin treatment to achieve adequate egg count reduction, demonstrating a practical tension between parasite management efficacy and environmental stewardship. For practitioners managing horses at pasture year-round, this work underscores the challenge of maintaining low parasite burdens in extensive systems and suggests that single-drug protocols may be inadequate, necessitating either strategic polypharmacy or alternative grazing management strategies to reduce transmission pressure.
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Practical Takeaways
- •Year-round grazing systems in Nordic conditions require multi-drug parasite management strategies; relying on a single anthelmintic (pyrantel) will not adequately control small strongyle populations despite regular monitoring and treatment
- •Summer-autumn represents a high-risk period for cyathostomin egg excretion in this grazing system, warranting intensified monitoring and management during these seasons
- •Body condition alone is not a reliable indicator of cyathostomin burden in grazing horses; fecal egg count monitoring remains essential for treatment decisions
Key Findings
- •Cyathostomin egg excretion was highest during summer-autumn and increased year-on-year despite pyrantel treatment at >200 EPG threshold
- •Multiple parasite species (5 endoparasite and 1 ectoparasite types) were detected in horses maintained in year-round grazing system over 2.5 years
- •No significant relationship was found between cyathostomin EPG and body condition score in this population
- •Pyrantel monotherapy was insufficient to control cyathostomin egg excretion; moxidectin supplementation was required, compromising the biological diversity conservation goal