Equine atypical myopathy caused by hypoglycin A intoxication associated with ingestion of sycamore maple tree seeds.

The paper discusses a study that links equine atypical myopathy (EAM), a disease in horses, to the consumption of seeds from the sycamore maple tree, which contain the toxin hypoglycin A.

Objective and Methods of the Study

In this study, the researchers aim to examine the hypothesis that equine atypical myopathy (EAM), a muscle disease in horses, is caused by hypoglycin A (HGA) ingestion, which comes from the seeds of the Sycamore maple tree. This toxin, they propose, causes an acquired multiple acyl-CoA dehydrogenase deficiency in the horses, a disruption in their ability to metabolize certain fats and proteins.

• The researchers used a case study approach. They examined a 2.5-year-old mare that exhibited signs of the disease—muscle stiffness and changes in posture—and had recently consumed Sycamore maple tree seeds.
• The team performed a necropsy and histopathology (microscopic examination of tissues) on the deceased horse, comparing it to three healthy geldings (castrated male horses).
• The chemicals in the mare’s blood and urine, post-mortem, were analyzed using a specialized type of liquid chromatography.

Results of the Study

The study yielded several significant findings:

• The mare’s macroscopic (visible to the naked eye) examination found seed fragments from the Sycamore maple tree in the stomach.
• There was evidence of severe myopathy (muscle disease), particularly in the rib, deltoid, and trapezius muscle groups.
• Microscopically, the muscle tissue showed signs of acute rhabdomyolysis — a rapid breakdown of damaged skeletal muscle — with accumulated fat droplets in the damaged muscle cells.
• Significant increases in certain metabolites were found in the urine and blood, indicating the presence of HGA, the toxic ingredient in Sycamore maple seeds.

Conclusions of the Study

The study’s results back the initial hypothesis: ingestion of hypoglycin A through Sycamore maple tree seeds is likely to be a cause of equine atypical myopathy (EAM) in horses due to the induced multiple acyl-CoA dehydrogenase deficiency. This deficiency interferes with their ability to break down and use certain types of proteins and fats.

The researchers’ findings imply a clear relationship between the consumption of Sycamore maple tree seeds and EAM, drawing attention to a potential intoxication source for horses that could lead to severe muscle disease.