Protect your horse against sycamore poisoning (Atypical Myopathy) this autumn

September 22, 2021

One of Towcester’s equine vets, Gwen Davies, shares some important seasonal information on Atypical Myopathy.  Discover what it is and what you need to do to prevent or deal with the symptoms of this life threating condition as autumn approaches.

What is Atypical Myopathy?

Atypical Myopathy, also referred to as Seasonal Pasture Myopathy, is a rare but often fatal muscular condition seen in horses and ponies in the UK. It is caused by ingestion of sycamore seeds, seedlings or leaves, which contain the toxin Hypoglycin A (HGA).

Atypical myopathy It is most commonly seen in horses grazing bare pasture in the autumn when the sycamore seeds have dropped, or in the spring when the seedlings are growing. Some individuals seem to be more susceptible than others, especially young adults, but several horses in the same group grazing the same pasture can be affected.

If you suspect your horse has ingested sycamore seeds/leaves or if you spot any of the clinical signs below, please contact our vets immediately.

Contact our equine vets now

What are the symptoms of Atypical Myopathy (Sycamore Poisoning)?

  • Weakness and difficulty walking or even standing
  • Stiffness
  • Muscle tremors
  • Profuse sweating
  • High heart rate in the absence of exercise
  • Difficulty breathing
  • Depression and low head carriage
  • Brown or dark red urine

Can we treat Atypical Myopathy?

Affected horses can deteriorate within hours, and prognosis is generally poor. For this reason, veterinary assistance must be sought urgently for suspected cases.

Intensive treatment is critical to maximising the chances of survival, including intravenous fluid therapy, glucose and vitamin supplementation, pain relief and nursing care.

Horses that remain standing, eating and survive for 10 days are more likely to recover.

How can you prevent Atypical Myopathy?

The safest method of prevention is to remove toxin-containing seeds and seedlings from the environment to stop ingestion. During the autumn months clear sycamore seeds from pastures or fence off areas where sycamore seeds have fallen. Be  aware that even fields without sycamore trees can still have seeds blown over. During spring, the most up to date recommendation is to mow and dispose of all sycamore seedlings. Some herbicides are available on the market to kill sycamore seedlings, but it has been found that the toxin can remain in dead seedlings for many months, so these must still be disposed of appropriately.

Other ways to reduce the risk include supplementation of forage if the pasture is bare, ideally feeding hay/haylage off the ground (using mats, tubs or feeders), and limiting the grazing time to less than 6 hours per day.

For more information or if you have any concerns reading sycamore seed ingestion, please don’t  hesitate to call the practice on 01327 811 007 and speak with one of our veterinary team.

Gwen Davies BVMedSci BVM BVS MRCVS is one of Towcester’s team of equine vets, you can find out more about Gwen and our other equine vets on our Team pages

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