There is still a lot about this disease which is not fully understood and much research is ongoing. Outbreaks of AM largely occur in Autumn and it has been strongly linked to a toxin (called hypoglycin A) within the leaves and seeds of the maple family.
Unfortunately for us in the UK, Sycamore tress fall into this family. We do get other members of the Maple family in this country as well such as the Box Elder but they are not native. Sycamore trees are obviously very common but it is very difficult to predict the risk to your horses even if they are grazing in a field surrounded by Sycamores. This is because the amount of toxin in the leaves and seeds varies between trees and also between seeds/leaves of an individual tree. The chance of your horse getting AM, therefore, seems to depend on the amount of seeds/leaves they ingest as well as the concentration of toxin that is in those seeds/leaves they have ingested.
Risk factors for AM
- Strong winds often precede outbreaks as more leaves/seeds are blown onto pasture.
- Affected horses obviously need to be grazing.
- Autumn time.