Detection of hypoglycin A in the seeds of sycamore (Acer pseudoplatanus) and box elder (A. negundo) in New Zealand; the toxin associated with cases of equine atypical myopathy.

This research study discusses the presence of hypoglycin A, a potent toxin, in the seeds of sycamore maple and box elder trees in New Zealand, and its association with cases of atypical myopathy – a fatal muscle disorder, in horses.

Research Methodology

In the course of this research, a stratified sampling of tree seeds was done across New Zealand coupled with an examination of historical and current cases of equine atypical myopathy. Furthermore, blood samples from affected horses and healthy controls were taken and analysed for the presence of hypoglycin A and specific profiles of acylcarnitines—the established diagnostic markers for atypical myopathy.

• Four horses presenting symptoms consistent with acute muscle damage were identified, and cases of atypical myopathy were reported where sycamore maple seeds (a known source of hypoglycin A) were present.
• Seeds were collected from trees across New Zealand associated with these atypical myopathy cases and analysed for the presence of hypoglycin A.
• Notably, serum samples were taken from the affected horses and were compared with samples from four unaffected horses. The serum was tested for hypoglycin A, as well as specific profiles of acylcarnitines and activities of creatine kinase and aspartate aminotransferase—both being important indicators of muscle damage.

Findings

The serum analysis found high activities of creatine kinase and aspartate aminotransferase, an increased concentration of selected acylcarnitine profiles, and the presence of hypoglycin A in the diseased horses but not in the healthy controls.

• Hypoglycin A was detected in 10 out of 15 samples collected from the seeds of sycamore maple and box elder trees located throughout New Zealand.
• The analysis showed a clear link between the instances of atypical myopathy in horses and areas where samaras – seeds of some Acer species – containing hypoglycin A were present. This confirmed the suspicion that sycamore and box elder trees could be a source of the hypoglycin A associated with this disease.

Implications

Based on the results, in instances of horses exhibiting clinical and biochemical signs of severe muscle damage, the environment should be analysed for the presence of sycamore and box elder trees. Horses should be prevented from grazing on Acer species’ seeds, especially in the autumn. By doing so, the risk of horses contracting atypical myopathy can be significantly reduced.