WHAT IS ATYPICAL MYOPATHY?
Atypical Myopathy (AM) is caused by horses eating sycamore seeds, leaves or seedlings that contain a toxin called hypoglycin A. This toxin results in severe muscle damage which can be life-threatening.
HOW MUCH SYCAMORE DOES MY HORSE NEED TO EAT TO BECOME POORLY?
The toxin is not present in all sycamore trees. The amount varies from tree to tree and from year to year. Therefore, there is no ‘safe’ amount. However, sycamores taste bitter so horses don’t tend to eat them when there is other food available. Young horses are more likely to eat sycamore seeds than older horses.
It is possible to test for the levels of Hypoglycin A in sycamore seeds, seedlings and leaves to see if your paddocks are at risk. You can send samples directly to the Royal Veterinary College for testing.
WHAT ARE THE CLINICAL SIGNS?
- Depression
- Weakness
- Muscle tremors
- Stiffness/not wanting to move
- Fast/irregular heart rate and rhythm
- Dark red/brown urine
- Difficulty breathing
- Colic
HOW WILL MY VET DIAGNOSE ATYPICAL MYOPATHY?
The diagnosis of atypical myopathy is based on the history of access to sycamore seeds, leaves and seedlings, compatible clinical signs and a blood test to look for muscle damage.
There is also a blood and urine test to identify the toxin in horses’ systems which can be used to confirm the diagnosis.
HOW IS IT TREATED?
Unfortunately, there is no cure, the only treatment is supportive therapy and nursing care.
This usually includes fluid therapy, pain relief and supplements to limit muscle damage.
Early and intensive medical management is vital to save affected horses. The likelihood of survival depends on the extent of muscle damage.
For severe cases, the prognosis is very poor with only 10-25% of horses surviving.
HOW CAN I PREVENT ATYPICAL MYOPATHY?
- By stopping your horses from eating sycamore seeds, leaves and seedlings.
- Fencing off the area around trees and clearing paddocks
- Feed hay when grass is low
- Remove sycamore trees from paddocks if possible
- Remember: seeds (helicopters) can travel up to 200 yards from the trees!