Keep your horses away from sycamore trees — that’s the warning from vets following an increase in cases of atypical myopathy this autumn.
The condition, which affects the muscles, can often be fatal.
The Atypical Myopathy Alert Group, a surveillance group based in Liege, Belgium, issued a warning to vets last month after a high prevalence of the disorder was noted across Europe, including the UK and Ireland.
Recent research in the USA linked the condition to the toxin hypoglycin A, which is found in the seeds of trees, including the box elder and sycamore.
But Dr Celia Marr, editor of the Equine Veterinary Journal, told H&H that the toxin — whose abundance varies widely, even within seeds from the same tree — may not be limited to these maple species.
“Only the sycamore tree has been investigated,” she said. “It is possible that other trees in the UK also contain this toxin.”
Equine vet Karen Coumbe advised owners to be cautious.
“It is hard to know whether it is associated with more sycamore seeds than normal after a warm summer or more falling at once with the stormy weather,” she said.
“I would recommend reducing horse access to sycamore seeds and fallen leaves by changing grazing where possible, fencing off areas of leaf fall or feeding supplementary hay to reduce grazing in danger areas.”
Equine vet Andy Durham said that, although he has seen relatively high numbers of cases this autumn, they are less severe than in the past.
“Four years ago, 95% of cases died, but this year I think 75% will survive — and I am unsure why,” he said. “Perhaps the toxin is less concentrated.”
The onset of the disease can be extremely rapid, with some horses being found dead in their fields. Outbreaks of the disease tend to be seasonal, with most cases occurring in the autumn.
Signs include muscular weakness and stiffness, dark urine, fatigue, colic-like signs and trembling.