The study, Understanding equine helminth transmission through integrated diagnostics and management assessment across five UK premises, has been published in Equine Veterinary Education and was co-authored by Tim Mair, CVS Equine Veterinary Director and Head of Hospital and Specialist in Equine Internal Medicine and Equine Surgery (Soft Tissue) at Bell Equine Veterinary Hospital.
The collaborative study between Bell Equine Veterinary Clinic and Austin Davis Biologics investigated parasite infection risk, diagnostic results and management practices across five equine premises in southern England. Bell Equine selected participating client yards, carried out faecal worm egg counts and collected samples, while Austin Davis Biologics performed small-redworm blood and tapeworm saliva tests. The project received ethical approval from the CVS Ethics Board.
Researchers collected data from 180 horses, using questionnaires completed by owners and yard managers to record horse demographics and management practices. Strongyle faecal egg counts (FECs) were performed during summer and autumn, using a modified McMaster technique, while serum antibody testing for cyathostomins and saliva antibody testing for Anoplocephala perfoliata were undertaken in winter.
The results demonstrated considerable variation in FECs and parasite-specific antibody levels between premises, reflecting differences in parasite exposure and management practices. Diagnostic outcomes were associated with several premise-level factors, including dung removal, frequency of dung removal, harrowing and co-grazing with non-equine species.
Importantly, regular dung removal was consistently associated with lower parasite indicators. This included fewer horses recording FECs of 200 eggs per gram or above and lower small-redworm antibody scores. For tapeworm infection, frequency of dung removal was also associated with saliva test results. Horses grazing paddocks where dung was removed more than once a week were less likely to test positive than those on paddocks where dung was removed less than once a week.
In contrast, harrowing was associated with higher FECs and antibody scores, including in circumstances where dung had not been effectively removed. Co-grazing with non-equine species was associated with lower parasite indicators, although the researchers caution that this finding is difficult to generalise because co-grazing occurred at only one of the five participating premises.
The research also found that management differences could result in substantially different parasite risks even for horses based on the same yard.
Another important aspect of the study was the use of multiple diagnostic approaches, highlighting the different information individual tests can provide. While FEC measures egg shedding from mature worms, it does not reflect total cyathostomin burden. Small-redworm blood testing provides information relating to cumulative exposure or burden, while tapeworm testing produced a different pattern of results in relation to prevalence and management variables. Together, these findings emphasise the importance of parasite-specific assessments rather than reliance on a single diagnostic measure.
The findings align with current UK equine parasite-control recommendations and provide empirical support for core principles underpinning the CANTER guidelines, particularly combining risk assessment, diagnostic monitoring and effective pasture management to reduce parasite transmission and enable more targeted use of anthelmintics. This is particularly important against the backdrop of increasing anthelmintic resistance, which the paper identifies as a growing threat to equine health and welfare and a key reason for adopting sustainable, evidence-based parasite control.
The authors acknowledge that the study involved only five premises in southern England, potentially limiting how widely its findings can be generalised, and that reliance on owner-reported management information may have introduced reporting or classification bias. Nevertheless, the research concludes that combining parasite diagnostic results with assessment of on-site management practices can provide valuable insight into the factors associated with helminth infection risk and support management strategies designed to reduce pasture contamination and parasite transmission.
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