Atypical Myopathy in Horses

November 21, 2014

IMG_0243Donaldsons are very much a mixed Veterinary Practice, treating Domestic Pets, Farm animals and Horses. Our Horse Vets have recently treated a number of horses for an unusual condition called Atypical Myopathy. The condition is caused by a toxin found in sycamore seeds, and is a devastating disease that destroys a horse’s skeletal and heart muscles.

The severity of the disease and the chances of recovery for the affected horse depends on which muscles are affected and to what extent they have been damaged. It is often fatal and can be misdiagnosed as colic. Atypical Myopathy can affect horses of any age and outbreaks occur most commonly in the autumn.

A toxin present in the seeds of the Sycamore Tree. In the past ten years, approximately 20 European countries have reported incidents of the disease.

The toxin is called hypoglycin A and it is present, in varying concentrations, in the leaves and the helicopter-shaped seeds of the sycamore tree; there is evidence that the weather can affect the level of toxin produced by the tree and not all seeds contain the same level. Horses that suffer from the disease are often kept on bare pasture surrounded by trees, without access to supplementary forage.

Affected horse present with muscle trembling and stiffness, can be weak and lethargic and may be found lying flat out in the paddock. If the disease has affected the heart and respiratory muscles, the horse will have laboured breathing and an elevated pulse. If muscle breakdown is extensive the urine will be dark in colour.

There is no antidote for hypoglycin A poisoning – treatment consists of managing the effects of the poison on the body, flushing out the horse’s system and maintaining hydration to prevent further damage. Nursing and palliative care are crucial for recovery and early diagnosis is critical. Even with intensive Veterinary management, around 50% of cases are fatal with affected ponies appearing to have a worse prognosis than horses, perhaps due to the relative size of their muscles.

What can you do to protect your horses from Atypical Myopathy? Learn to identify the sycamore tree and its seeds, and fence them off to keep horses away. Clear up seeds regularly as part of your pasture management programme and provide supplementary forage so that your horses are less likely to eat any seeds remaining in the field.

Leave a Reply