05/11/2026
🔷🐴‼𝑾𝑯𝑨𝑻 𝑰𝑺 𝑨𝑻𝒀𝑷𝑰𝑪𝑨𝑳 𝑴𝒀𝑶𝑷𝑨𝑻𝑯𝒀‼🐴🔷
Atypical Myopathy is a devastating muscle disorder arising from ingestion of components of the Sycamore tree (usually seeds or shoots, but also leaves). A toxin contained within these component parts (Hypoglycin A) causes systemic damage to metabolising cells, generally affecting cells with high energy demand first (muscle cells). A relatively miniscule amount of Hypoglycin A causes severe consequences, which is the reason for such a high fatality rate associated with the disease (>75%). Individual horses vary in susceptibility to the clinical signs from the disease and individual trees produce seeds and seedlings with different levels of Hypoglycin A.
𝑪𝑳𝑰𝑵𝑰𝑪𝑨𝑳 𝑺𝑰𝑮𝑵𝑺
Equines generally present with general weakness - progressing to an inability to stand, muscle tremors, sweating, colic signs, dullness and depression, low head carriage and dark red/brown urine. A history of access to pastures with Sycamore trees is common with ingestion of seedlings (usually in Spring) or seeds/leaves (Autumn/Winter) - although in high winds, the seeds can travel for several hundred meters so there may not be direct access to horses. Clinical signs usually occur between 6 and 72 hours following ingestion.
𝑷𝑹𝑬𝑽𝑬𝑵𝑻𝑰𝑶𝑵
Removing any Sycamore trees or fencing off a large area surrounding any trees to reduce the likelihood of ingestion can help reduce the risk of Atypical Myopathy as well as physically clearing any fallen seeds/leaves. During Spring when seedling ingestion is more common - removing seedlings by hand is the best way (spraying/moving does not help unless all cuttings/dead plants are also removed as the toxin remains). Provide supplementary forage during Autumn months when grazing is sparse to prevent eating any seeds/leaves. If you do have Sycamore trees on your property/pasture, the Royal Vet College offers a testing service which helps test the toxin levels of plants - further information on this can be found on the RVC Website under the Neuromuscular Disease Laboratory Section.
‼If you suspect your horse has ingested any Sycamore seeds/leaves or is presenting with any of the above clinical signs, please call us for further advice, even with aggressive treatment and early intervention, success rates of recovery following treatment are very low. Please do not hesitate to contact us if you have any questions or concerns.‼
