Recent weather patterns across the UK — including unseasonably strong winds and heavy rainfall — have led to an earlier-than-usual drop of sycamore seeds. While picturesque in autumn, these “helicopter” seeds can pose a serious, sometimes fatal, health risk to horses: Atypical Myopathy (AM).
What is Atypical Myopathy?
Atypical Myopathy is a potentially fatal condition caused by ingestion of toxins found in sycamore seeds (and seedlings), specifically hypoglycin A. Once ingested, the toxin interferes with the horse’s ability to metabolise fats and energy, leading to rapid muscle breakdown. The condition is most commonly seen in the autumn when seeds fall or in spring when seedlings emerge.
Why the Risk is Greater Now
This year’s unsettled weather has triggered a premature drop in sycamore seeds, increasing the risk period earlier than usual. This means that horse owners and yard managers must be extra vigilant—even if AM isn’t typically a concern this early in the season.
Steps to Minimise the Risk
If you have sycamore trees on or near your grazing land, take immediate action:
-
Identify Trees: Familiarise yourself with the appearance of sycamore trees and their seeds. Consult an arborist if you’re unsure.
-
Inspect Grazing Areas: Check fields daily, especially after storms or high winds, for fallen seeds.
-
Check Water Sources: Seeds can fall into or be blown into water troughs. Remove any debris daily to prevent accidental ingestion.
-
Provide Adequate Forage: Horses are more likely to consume sycamore seeds if grazing is sparse. Providing extra hay or forage can reduce the temptation.
-
Restrict Access: Fence off or avoid turnout in areas heavily contaminated with seeds. This can be a short-term but effective safety measure.
Know the Signs of Atypical Myopathy
Atypical Myopathy has a rapid onset and requires urgent veterinary attention. Key symptoms include:
-
Sudden weakness or stiffness
-
Muscle tremors
-
Dark, coffee-coloured urine
-
Sweating
-
Lethargy or depression
-
Reluctance to move or lie down
If you notice any of these signs in your horse — particularly after exposure to sycamore seeds — contact your vet immediately. The survival rate improves significantly with early intervention.
Stay Informed and Prepared
Early awareness and prevention are crucial. While not every sycamore tree poses a problem, the presence of seeds in grazing areas during this period of unusual weather heightens the risk.
Yard managers and horse owners alike must remain vigilant, especially in mixed grazing fields or woodland edges. Taking proactive steps can help prevent a devastating health emergency for your horses.
For more information on atypical myopathy and sycamore toxicity, consult your vet or visit resources provided by equine welfare organisations, such as this leaflet from the BHS.