Riders using wormers in an attempt to treat headshaking have been warned of the possible consequences of giving such drugs without veterinary advice.

Owners have been seen on social media and forums discussing the possibility of using increased doses of wormers to treat the frustrating condition.

Vet Wendy Talbot has advised that wormers are not licensed to treat this condition and it must only be done under direct veterinary prescription

“I can’t find any evidence to back [this treatment] up,” she told H&H.

“There’s been lots of talk online; people are interested as they seem to think it does improve headshaking behaviour in some horses, but this is anecdotal and there’s no reliable evidence.

“It’s so important always to act only under the direction of your vet as even if something’s suitable for one horse, it may not be for another.”

Dr Talbot, who works as the national equine veterinary manager for animal health company Zoetis, said that if a horse had been wormed recently, it is possible an extra or double dose is not licensed for use in these circumstances and could cause an adverse reaction.

“And we want to reduce indiscriminate use of wormers in all situations and only use the right wormer for the right condition and at the right time,” she added, explaining that the basis of all worming programmes is treating only those horses who need it, owing to the risk of developing resistance to the active ingredients. If worms become widely resistant to current wormers, horse owners will be left without any treatment options to deal with equine worm burdens.

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“Headshaking is very distressing for everyone, but no one could recommend that owners self-prescribe drugs or dosages that have not been fully tested and shown to treat a particular condition. All treatment should take place under veterinary supervision.”

Dr Talbot advised owners to consult their vets or a suitably qualified person who is authorised to advise on and prescribe wormers, to formulate an appropriate worming programme for each horse, which takes into account its age and circumstance as well as faecal egg counts to determine its worm burden.

“Wormers are prescription-only medicines,” she said. “You’re not supposed to change the scientifically determined correct dosage yourself, and even more so because of the potential dangers to your horse’s health.”

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In this week’s Horse & Hound magazine, out on 28 June, is a full report from the Hickstead Derby meeting, a six-page report from Royal Ascot, a feature on the much-discussed whip rules and, in this week’s ‘vet clinic’, find out how to spot the signs of sand colic.