Lethal Sycamore maple intoxication in a grazing three-month-old foal.
Authors: Janzen N, Sander J, Terhardt M, Mallek M, Smith H, Witt P, Theelen M J P
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Lethal Sycamore Maple Intoxication in a Grazing Foal Certain Acer species pose a significant poisoning risk to grazing horses through accumulation of hypoglycin A (HGA) and methylencyclopropylglycine (MCPRG) in leaves, seeds, and shoots—toxins capable of triggering atypical myopathy with fatal consequences. Janzen and colleagues documented a clinical case of a three-month-old foal that developed severe myopathy after ingesting maple material whilst at pasture, detailing the clinical presentation, diagnostic findings, and progression of toxicosis. The case illustrates how rapidly life-threatening disease can develop in young stock exposed to maple toxins, with clinical signs reflecting the characteristic muscle damage and metabolic dysfunction associated with atypical myopathy. For equine professionals managing grazing horses—particularly foals and young animals with less dietary discrimination—awareness of local Acer species distribution and prompt recognition of myopathy signs (weakness, muscle pain, dark urine, recumbency) are essential for timely intervention, whilst pasture management to exclude or remove maple trees remains the most effective preventive strategy.
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Practical Takeaways
- •Remove or fence off Acer maple species from pastures where foals and horses graze, particularly during seasons when leaves and seeds are accessible
- •Monitor young foals for signs of myopathy including muscle weakness, recumbency, and dark urine when maple trees are present in grazing areas
- •Educate horse owners that even small amounts of maple toxins in certain Acer species can prove rapidly fatal in young animals
Key Findings
- •A three-month-old foal developed life-threatening myopathy from ingesting Acer species maple leaves, seeds, and shoots
- •Maple toxin contains hypoglycin A (HGA) and methylencyclopropylglycine (MCPRG) which cause atypical myopathy in grazing horses
- •Young foals are susceptible to lethal poisoning from maple tree ingestion during grazing