Equine Atypical Myopathy

What to look for and what to do

There has been a recent surge in cases of atypical myopathy (seasonal pasture myopathy) even in areas where the disease has not previously been reported. Research carried out within the last 12 months has shown that atypical myopathy is caused by a toxin (Hypoglycin A) in the ‘helicopter’ seeds of the sycamore tree (Acer pseudoplatanus). The warm summer and early autumn has seen an abundance of seeds within sycamore trees. The recent high winds and heavy rain has resulted in large numbers of seeds falling from trees in a very short period of time posing a risk to horses grazing on surrounding fields.

If horses are grazing on pasture surrounded by sycamore trees or if large numbers of seeds blow into field’s clients can:

  • Consider fencing off areas around trees 
  • Removal of sycamore seeds 
  • Reduce stocking density within pastures 
  • Stable horses and turn out for short periods of time
  • Supply extra forage hay or haylage especially if the pasture quality is poor; horses will not choose to eat the seeds if there is sufficient grass. 

You are encouraged to walk around your pasture to identify any sycamore trees within or adjacent to grazing land so that you can take steps to reduce the risk of this disease. You should discuss the risks with your veterinary surgeon who will be able to advise about measures that may be appropriate your their horses.

Signs to look for are:

  • stiffness
  • unwilling to move
  • difficulty swallowing
  • colic
  • trembling
  • weak and passing dark coloured urine

Young horses are possibly more at risk. Given how quickly this disease acts, if you are in any doubt please contact us immediately.

Confirmed cases can be reported to – University of Liege here

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