Vets warn horse owners as first cases of fatal sycamore poisoning are confirmed

As vets in the UK see this year’s first cases of fatal muscle disease in horses that have eaten sycamore seeds, the British Veterinary Association (BVA) and British Equine Veterinary Association (BEVA) are warning horse owners to take extra precautions as autumn winds bring down seeds into pastures.

British Veterinary Association (BVA) and British Equine Veterinary Association (BEVA) warning
British Veterinary Association (BVA) and British Equine Veterinary Association (BEVA) warning

Sycamore seeds are toxic and can cause Seasonal Pasture Myopathy (SPM), previously known as Atypical Myopathy (AM), a fatal muscle disease in horses that, until recently, was of unknown origin. Yet recent research (2013-14) showed SPM to be caused by the toxin hypoglycin A, contained in tree seeds (fruit) including that of the sycamore.

BVA President Sean Wensley said: “SPM is a disease that is extremely distressing for both the animal and the owner of the horse affected. BVA is working closely with our colleagues in BEVA, who deal with the aftermath of sycamore poisoning in horses all too often throughout the autumn, to ensure we get timely advice to owners to prevent their animals suffering in this way.”

High winds during autumn 2014 resulted in considerable contamination of pastures with sycamore seeds. Data from the National Equine Health Survey showed owners reported a four-fold increase in cases last year.

BEVA President Mark Bowen said: “In the last two years our understanding of this awful condition in horses has increased considerably. We now know that sycamore seeds contains the highly toxic agents that cause SPM and this means there are practical things that we can advise owners to do that minimise the risk to their animals. BEVA members know from experience the suffering that horses with SPM endure and the anguish this causes owners. We urge owners to act on the advice that BEVA and BVA have issued.”

Horses that develop SPM are usually kept in sparse pastures with an accumulation of dead leaves, dead wood and trees in or around the pasture and are often not fed any supplementary hay or feed. While the seeds may not be directly palatable, horses grazing on poor quality pasture may ingest considerable numbers of them. BVA and BEVA advise owners to:

* Restrict access to seeds by using temporary fencing.

* Ensure horses have access to good quality uncontaminated pasture.

* Move horses off pasture at times of risk.

* Provide supplementary feed in the field to minimise the risk of horses being tempted to ingest seeds.

* Avoid leaving wet hay on the ground where it will rot and potentially trap seeds.

* Discuss the risks and how to identify early clinical signs of AM with your veterinary surgeon.

* Be aware that a field without sycamore trees can still contain seeds spread by high winds or flood water.

* Do not prune seed laden trees as this can lead to massive pasture contamination and further increase the risk to horses.