By now we know that the maple sycamore tree (Acer pseudoplatanus) is the plant responsible for atypical myopathy (similar to seasonal pasture myopathy) in horses. But the same Belgian team who made that discovery is now revealing ways to test the prognosis of affected horses—and they’re finding that it has nothing to do with how much toxin the horse ingests.

“The intake of hypoglycin A in the fruits of these trees leads to atypical myopathy, but some horses can have very large quantities of the toxin in their systems and survive, whereas others can have very little and die,” said Dominique-Marie Votion, DVM, PhD, of University of Liege in Belgium. “So knowing the levels of hypoglycin A in the horse’s bloodstream alone does little good for predicting its chances of recovery.”

Votion presented her most recent work on atypical myopathy (AM) during the 2015 French Equine Research Day held March 12 in Paris.

A better prognostic tool is looking at acylcarnitines in the horse’s blood, Votion said. Acylcarnitines are essentially backlogged fat metabolites. When a horse ingests hypoglycin A, it metabolizes into a toxin that upsets the animal’s energetic metabolism—hence, the presence of the excess acylcarnitines.

Votion’s team recently validated the methodology for analyzing hypoglycin A in blood samples. They investigated samples from 18 horses admitted to the Liege Veterinary Hospital in the fall 2013 for atypical myopathy (five of which survived) and five horses admitted for exercise-induced myopathy, or exertional rhabdomyolysis—also called tying-up. They found no h