As autumn progresses, vets are calling for greater awareness of the often fatal seasonal condition atypical myopathy.

On 16 October, RVC Equine said they had seen five cases of the condition in 72 hours and urged owners to be aware of the signs.

The onset of the disease can be extremely rapid, with some horses being found dead in their fields.

Signs include muscular weakness and stiffness, dark urine, fatigue, colic-like signs, shivering, sweating and trembling.

H&H vet adviser Karen Coumbe said her surgery saw its first case of the autumn disease last week.

The illness weakens the muscles of the skeleton and heart.

Aisha-Lee Jackson’s three-year-old Welsh section D Nevaeh was in good health before she died from atypical myopathy last November. She contacted H&H to raise awareness of the disease.

“At first Nevaeh appeared to show signs of colic, however on attempt to move her it became very clear there was something very wrong; she was unable to move her legs,” said Ms Jackson.

“I can only wish that I had heard of this disease before, and hope that by sharing my story, I can prevent the heartbreak and suffering of another horse/owner.

“I feel there is not enough awareness of it. As we are in autumn, when more leaves are on the ground, I want to highlight it to other owners.”

Last year, research by the University of Liege linked the mysterious fatal condition to the sycamore tree.

And last autumn, British vets put out a warning to keep horses away from these trees after a rise in cases.

The university recorded 415 cases across Europe between last autumn and this spring.

Earlier this year, experts in Belgium warned cases were on the rise, and the National Equine Health Survey (NEHS) included a question on the condition for the first time in response to an increase in reports.

Run by the Blue Cross, data was collected from 11,002 horses across the UK in May. Vets were asked to record the number of confirmed cases they had had in the previous year.

Thirteen cases were recorded — meaning the first estimate of the prevalence of atypical myopathy in the UK is 0.1%.

But more research is needed. Prof Josh Slater, who analysed the data, said: “The number of cases of this disease that occur each year are not known. Though NEHS has provided a snapshot, we need to capture data from a much larger number of horses to know how common this disease truly is across the UK as a whole.”

In the meantime owners need to be vigilant.

“Owners need to be aware of the possible risk of grazing near suspect trees, such as sycamores,” added Karen Coumbe. “Where possible they should be avoided completely.”

For more on the condition, see H&H’s guide to atypical myopathy.