Limits on horse dewormer sales suggested as resistance nears crisis point

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A leading veterinarian says 20 years of research and education had failed to change horse owner behaviour, and if an equine welfare crisis was to be averted the supply of wormers might have to be limited.
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The wider equine industry has failed to appreciate the importance of anthelmintic resistance and the next step might be the restriction of access to de-wormers, a leading veterinarian says.

Speaking at Britain’s National Equine Forum last week, David Rendle, President-Elect of the British Equine Veterinary Association, made the point that 90% of vets surveyed believed restricting the availability of de-wormers would help to improve horse welfare yet he feared the wider industry “don’t appreciate the importance of the situation”.

Rendle maintained that education alone didn’t work as it was preaching to the converted and the science of human behaviour indicated that sufficient change will not result unless there is some restriction on access to de-wormers.

He presented alarming figures that 120,000 faecal worm egg counts were used per year compared to 1.13 million doses of de-wormer being sold, equating to 11 doses for each test (rather than an average of about four tests per wormer if a targeted approach was being followed).

Some 20 years of research and education had failed to change horse owner behaviour sufficiently and he suggested that if an equine welfare crisis was to be averted the supply of wormers would have to be limited to use within a diagnostic-led plan that was revised every year.

Rendle added that the liberal use of de-wormer undermined the sector’s social license as some drug classes were ecotoxic and posed a real danger to invertebrates and aquatic life.

Delegates to the forum discussed the real and present risk of equine de-wormers no longer working if their use was continued in a non-targeted way, that is, given regularly rather than as required for an individual animal, based on information such as their age, clinical history, management and faecal worm egg count. A grave threat lay ahead unless the sector took collective, urgent action to reduce the critical health and welfare risks to horses posed by resistance.

Dr Claire Stratford, Head of the Efficacy Team and Anthelmintic Resistance Policy Lead and Dr Alison Pyatt, International Programme Manager and Training Centre Lead, both from the Veterinary Medicines Directorate, issued a stark warning. They explained that resistance was now being seen to all classes of de-wormer; that the more anthelmintic was used indiscriminately the more resistance would build up and this resistance could be transferred between yards.

“Uncontrolled, this will lead to critical health and welfare issues,” Stratford said.

The fragmented sector was a problem and there was a growing risk of not being able to graze horses on some pastureland as it would be contaminated with drug resistant parasites. A consistent pan-industry approach and best practice guidelines were needed urgently.

Claire Shand, Marketing Director at Westgate Labs, said there was absolutely no place for routine non-targeted worming. She said the science of faecal worm testing could help reduce the use of de-wormers but “it’s not just doing the test itself but it’s what is done with the results that counts”.

The results of faecal worm counts needed to be evaluated over time in all individuals within any group to enable an effective control plan to be developed. She also highlighted that the way pastures were managed could have a big impact on parasite burdens. Regular manure collecting, resting fields and cross grazing with sheep or cows were effective ways to help manage parasite burdens. She pointed out that harrowing was not an effective method in Britain.

“Don’t think just of our own horses, think of the bigger picture,” Shand said. “What will we do when the wormers stop working? Please don’t wait to find out.”

» The replay of NEF22 is available until March 31, for £20, or free to those registered for the event.

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