A new study conducted by the Equine Infectious Disease Surveillance (EIDS) Group at the University of Cambridge has revealed a significant increase in positive faecal worm egg counts (FWECs) among UK horses over the past 17 years. Published in the Equine Veterinary Journal, the findings raise crucial questions about parasite control strategies and the potential risks of anthelmintic resistance.
Key Findings from the Study
Researchers analysed FWEC test results submitted between 2007 and 2023 from 36 UK laboratories, with 18 laboratories also providing detailed insights into their testing methods. The study uncovered a steady increase in the proportion of positive FWECs, even when accounting for seasonal variations and differences in laboratory testing methodologies.
The increasing positivity rates present a challenge to targeted treatment strategies, where horses are only given wormers if their FWECs surpass a certain threshold. If these positivity rates continue to rise, more horses may be prescribed anthelmintics, potentially accelerating the development of parasite resistance – a growing concern in equine health.
Why Does This Matter?
More positive FWECs mean more treatments, but are they always necessary? The risk of overuse of wormers could lead to resistant parasite populations, making treatment less effective in the long run. Researchers stress the need to investigate the factors driving this increase and whether the rising positivity rates translate to more horses needing treatment.
Surveillance datasets provide valuable insights, but challenges remain. The study relied on laboratory test summaries, meaning researchers lacked key background data such as the age of horses, previous worming history, and environmental risk factors. Further research is needed to refine data collection methods for even better insights.
Expert Insights
Lead researcher Fleur Whitlock, MRCVS, emphasised the importance of continued surveillance:
“This paper highlights the remarkable achievements of two decades of sustained surveillance efforts, showcasing how data contributions and analysis can deepen our understanding and drive progress. It emphasises the critical importance of advancing the monitoring and interpretation of surveillance data to better address industry challenges, such as the growing concerns around anthelmintic resistance.”
Next Steps in Parasite Control
To combat the potential overuse of wormers and growing concerns about resistance, vets, horse owners, and industry professionals are encouraged to follow the latest guidance from British Equine Veterinary Association (BEVA) and CANTER, two leading organisations providing sustainable parasite control strategies:
Looking Ahead
The EIDS Group aims to refine equine parasite surveillance by enhancing data collection methods and addressing current knowledge gaps. These ongoing efforts will play a key role in preserving the effectiveness of wormers and ensuring the long-term health of the UK’s horse population.
For a detailed breakdown of the study, you can read the full open-access paper here: Equine Veterinary Journal.
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