“Desperate Need” to Reduce Wormer Use in Horses Following New Research

23 January 2024

Two surveys were recently organised by Project WORMS (Working to Overcome Resistance and Make for a Sustainable future). The aim was to investigate parasite control in UK horses, identify areas where management practices could be improved and look at whether vets can better target their advice.

We all know that over the years, the resistance to available worming drugs is present and increasing, with little or no new products being developed. Although many horse owners and yard owners are reducing worming medication with steps such as Faecal Worm Egg Counts (FWEC) this is not having enough of an effect to reduce resistance.

A spokesman for WORMS, a collaboration between VetPartners, CVS Group, IVC Evidensia and Equine Reproductive Services, supported by the British Equine Veterinary Association (BEVA), said: “The horse world could be left without effective anthelmintics in the near future, putting horses at an increased risk of parasite damage-related illnesses such as severe diarrhoea, weight loss and colic, which are currently preventable.”

The horse owner survey, completed by 4,233 people, found that 84% carry out regular faecal worm egg counts (FWEC), 40% routinely test for tapeworm, 73% poo-pick grazing and 22% graze with or alternate grazing with ruminants. Of those who do FWECs, 37% routinely worm horses at least once a year, regardless of results.

In the second survey, focusing on the breeding industry, 36% of stud managers said they have experienced parasite-related illness within the last year, most often weight loss, diarrhoea and colic. Over 20% were aware of wormer resistance on their premises.

Of those who said veterinary advice was “very important” when deciding whether to worm, nearly half used moxidectin and praziquantel as their first-line anthelmintic.

Julia Shrubb, deputy chair of VetPartners’ equine clinical board and a vet at Ashbrook Equine Hospital, said it is critical that horse owners, stud farms and veterinary surgeons work together to delay the onset of further resistance.

She said: “The information from the surveys is vital to give us a further understanding of how and why anthelmintics are given to horses. The surveys have identified areas where management practices can be improved and this will allow veterinary surgeons and SQP [suitably qualified person] professionals to give more appropriate and targeted advice and encourage responsible anthelmintic use.

“It is very encouraging that high levels of testing were reported, which underpins responsible anthelmintic use.”

Graham Hunter, IVC Evidensia equine group veterinary advisor, said a “huge educational piece” is needed on a targeted approach to wormer use.

Tim Mair, CVS equine director, added: “Resistance among horse parasites to the currently available wormers is widespread and increasing. We desperately need to reduce the overuse of these drugs, not only to stem the tide of resistance, but also to reduce the toxic effects that these drugs have on the environment.”

CANTER (Controlling Antiparasitic Resistance in Equines Responsibly), a group set up to tackle wormer resistance, recommends owners risk assess each horse’s likelihood of suffering as a result of parasites, and work with vets to ensure appropriate control programmes.

You can find guidance and resources on worm management on the Yard Owner Hub here: Worming and Parasite Control

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