A new video explains how worm resistance develops and how owners can take steps to slow its advance.
Resistance to worming drugs, known as anthelmintics, poses a major threat to the health and well-being of horses.
Wormer resistance is not a new problem – it was first recorded in sheep in the early 1980s.
Britain’s Westgate Laboratories, which offers a postal worm count service, says horse owners are starting to feel the impact of resistance, which will increase if they choose not to heed warnings about the need for sustainable use of drugs.
It joined the call for use of evidence-based parasite control programmes – only giving a wormer when the tests indicate it is warranted, and for specific seasonal problems such as encysted small redworm and bots.
It says, wherever possible, pasture management techniques should be employed to help break the life cycle of worms mechanically, by picking up dung, cross grazing and resting paddocks, rather than relying on chemical intervention.
A consultant vet to Westgate Labs, Carolyn Cummins, says getting parasite control right is important.
“Working as a first opinion equine vet I see horses every year that are suffering from a severe worm burden.
“This can be due to neglect or other underlying illnesses but more worryingly, in others, these are horses with owners who believe that they are worming their horses appropriately.
“Problems arise from worming at the wrong times of year, not using the appropriate wormer, under-dosing, or overuse of a particular wormer leading to resistance so that the drugs we have are no longer effective.
“A horse suffering with a severe worm burden can go from an apparently healthy horse to a severely ill one in a very short space of time, hence the importance of a regular testing regime.”