Samaras and seedlings of Acer pseudoplatanus are potential sources of hypoglycin A intoxication in atypical myopathy without necessarily inducing clinical signs.
Authors: Baise E, Habyarimana J A, Amory H, Boemer F, Douny C, Gustin P, Marcillaud-Pitel C, Patarin F, Weber M, Votion D-M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Sycamore Seeds, Seedlings and Atypical Myopathy Risk Atypical myopathy (AM) is a devastating condition affecting grazing horses, with sycamore seeds (Acer pseudoplatanus) implicated as a major source of the toxin hypoglycin A, though spring ingestion of seedlings may represent an underrecognised exposure route. This 2016 field investigation collected botanical and blood samples from eight AM-affected premises and five unaffected control sites, quantifying hypoglycin A concentrations in both plant material and equine serum using advanced biochemical techniques. The researchers detected hypoglycin A in all sycamore seeds and spring seedlings tested; affected horses showed serum levels of 5.47 ± 1.60 μmol/l, but critically, hypoglycin A was also identified in clinically healthy horses grazing pastures containing these plants—including one asymptomatic animal with a serum concentration of 7.98 μmol/l and two healthy co-grazers with AM-affected herdmates (0.43 ± 0.59 μmol/l). For equine practitioners, these findings underscore that toxin exposure alone does not guarantee clinical disease expression, making blood hypoglycin A testing a valuable screening tool for AM risk assessment and exposure confirmation in suspect cases, whilst highlighting the need to manage access to both sycamore seeds and emergent seedlings during high-risk seasons.
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Practical Takeaways
- •Sycamore samaras and seedlings are confirmed sources of hypoglycin A; removal or prevention of access to these plants on pastures with affected horses is essential
- •Horses grazing where sycamore trees are present may have detectable toxin in their blood without showing clinical signs, making them subclinically affected or at risk for disease development
- •Serum hypoglycin A testing can confirm exposure history when atypical myopathy is suspected, even in horses without overt clinical manifestations
Key Findings
- •Hypoglycin A was detected in serum of affected horses (5.47 ± 1.60 μmol/l) and also in clinically healthy horses grazing pastures with Acer pseudoplatanus (up to 7.98 μmol/l)
- •Hypoglycin A was present in all samples of both sycamore seeds (samaras) and spring seedlings collected from affected pastures
- •Two healthy horses co-grazing with atypical myopathy cases showed detectable serum hypoglycin A (0.43 ± 0.59 μmol/l) without clinical signs
- •Blood hypoglycin A concentration is useful for screening exposure to sycamore in suspected atypical myopathy cases