Atypical myopathy

Atypical Myopathy (AM) is a highly fatal muscle disease in grazing horses – mostly in Autumn and Spring – causing the destruction of respiratory, cardiac and postural muscles. It has been shown that the suspected toxin hypoglycin A is found in Sycamore seeds.

It appears that young horses are more susceptible, along with those grazing parched land.

AM has a fatality rate of 70% and once a horse is exhibiting signs the condition is typically already serious.

A few horses may recover with intensive care if early treatment is provided. Despite intensive veterinary treatment, severely affected horses may die.

How do we recognise the disease?

Early signs of the disease include lethargy, muscle weakness + trembling, colic-like signs which usually progresses to showing signs of stiffness. The urine from the horse becomes dark red in colour.

In severe cases horses become increasingly painful and are often found lying down and unable to stand. The onset of the illness can be extremely rapid and distressing, with some horses being found dead in their fields.

What you can do

In practical terms, reducing the ingestion of sycamore seeds is essential by:

  • Frequently inspecting fields to remove any seeds that have fallen from, or been blown from, nearby sycamore trees.
  • Fencing off areas around trees where sycamore seeds have fallen.
  • Keeping stock levels low.
  • Providing extra forage (hay or haylage) especially where grazing is limited.
  • Turn out for short periods of the day (ideally <6 hrs) and stable at night.

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