Samaras and seedlings of Acer pseudoplatanus are potential sources of hypoglycin A intoxication in atypical myopathy without necessarily inducing clinical signs.

Reasons for performing study: Ingestion of sycamore seeds (Acer pseudoplatanus) is the likely source of hypoglycin A in atypical myopathy (AM) but ingestion of seedlings in spring might also contribute to intoxication. Objectives: To test for hypoglycin A in seeds and seedlings collected on pastures where AM cases were reported and compare its concentration in serum of affected and healthy horses. Study design: Field investigation of clinical cases. Methods: Whenever present, samaras (the winged nuts that each contain one seed) and/or seedlings were collected from pastures of 8 AM cases and 5 unaffected horses from different premises. Two AM cases were each co-grazing with an apparently healthy horse. Acylcarnitines and hypoglycin A were quantified in blood samples of all horses involved in the study. Results: Hypoglycin A was detected in serum of AM (5.47 +/- 1.60 mu mol/l) but not in healthy controls pasturing where A. pseudoplatanus trees were not present. However, hypoglycin A was detected at high concentrations (7.98 mu mol/l) in serum of a clinically healthy horse grazing a pasture with seedlings and samaras and also in the 2 healthy horses co-grazing with AM cases (0.43 +/- 0.59 mu mol/l). Hypoglycin A was detected in all samples of seeds and spring seedlings of A. pseudoplatanus. Conclusions: Atypical myopathy can be associated with the ingestion of sycamore samaras and also ingestion of seedlings. Hypoglycin A can be detected in the blood of horses with no detectable clinical signs at pasture in which there is A. pseudoplatanus. Determination of hypoglycin A concentration in blood is useful for screening for exposure in suspected cases of AM.