Horse Owners Cautioned about Equine Atypical Myopathy - A Seasonal, Pasture-associated Disorder

Horses running in a fall pasture.
Horses running in a fall pasture. Sari ONeal

Newsdate: October 2, 2020, 11:00 am
Location: GILROY, Califoria

Equine Atypical Myopathy (EAM) is a seasonal, pasture-associated disorder of unknown etiology. The disease is characterized by a generalized degeneration of muscle fibers which can lead to sudden death due to collapse of the cardio respiratory system in over 90 per cent of cases.

Seeds of the sycamore maple tree.

Seeds of the sycamore maple tree

Equine Atypical Myopathy, a seasonal, pasture-associated disorder, is characterized by degeneration of muscle fibers which can lead to sudden death.
© 2013 by Famartin New window.

Affected horses can either die peracutely or show profuse sweating, muscle weakness, recumbency, difficulty breathing and death after 12 to 72 hours. Since the etiology is unknown no effective prophylaxis exists and affected horses can only be treated symptomatically.

Large outbreaks have been reported in Europe and in 2010, 224 new cases were reported. A very similar, if not the same disease has been observed in the United States.

Environmental factors such as regular access to pasture and certain weather conditions seem to influence the incidence of the disease which occurs seasonally, mostly in autumn with fewer cases in springtime and sporadic cases in winter.

Causes of EAM are thought to be ionophores, mycotoxins and phytotoxins and has been associated with ingestion of maple leaves covered with European tar spot and toxins from the seeds of the sycamore maple tree. Stress and metabolic imbalances might predisposes horses to develop the disease.

Young horses kept full time at pasture without any food supplementation are most frequently affected. Further risk factors as adjacent streams and trees, dead leaves and branches in pastures and wet windy, unpleasant chilly weather conditions.

Horse owners are advised to remove manure from pastures, provide clean drinking water and salt blocks and bring horses in from the pasture during rough weather.

About the Author

Flossie Sellers

Author picture

As an animal lover since childhood, Flossie was delighted when Mark, the CEO and developer of EquiMed asked her to join his team of contributors.

She enrolled in My Horse University at Michigan State and completed a number of courses in everything related to horse health, nutrition, diseases and conditions, medications, hoof and dental care, barn safety, and first aid.

Staying up-to-date on the latest developments in horse care and equine health is now a habit, and she enjoys sharing a wealth of information with horse owners everywhere.

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