June 10, 2020
Atypical Myopathy – June 2020
Atypical myopathy is a painful and potentially fatal muscle disease caused by a toxin found in the seeds of trees of the genus Acer, for example the sycamore tree and box elder tree. The disease is most commonly seen at this time of the year so it is important to take steps to prevent it!
Horses that develop AM are often kept on sparse pastures containing an accumulation of dead leaves, wood, and trees, and these animals often are not fed any supplementary hay or feed. The seeds are not palatable for horses but animals grazing on poor quality pasture may ingest sufficient amounts to result in signs of disease.
Horse owners are advised to identify these trees on or near grazing land and take steps to prevent the seeds falling where they are in reach of horses, including:
- Restrict access to seeds by using temporary fencing
- Ensure horses have access to good quality uncontaminated pasture
- Move horses off pasture at times of risk
- Provide supplementary feed in the field to minimize the risk of horses being tempted to ingest seeds
- Be aware that a field without sycamore trees can still contain seeds spread by high winds or flood waters
- Monitor horses closely to pick up any signs of a problem in the early stages