Mare’s brush with Atypical Myopathy likely cause of newborn foal’s death – report

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Seed pods from a sycamore tree on the ground in pasture. Ingestion of these seeds can prove toxic to horses.
Seed pods from a sycamore tree on the ground in pasture. Ingestion of these seeds can prove toxic to horses.

A case of Atypical Myopathy in a newborn foal has been reported in the Czech Republic, suggesting it may be possible for the toxin that causes the disorder to cross into the placenta or pass to the foal in the mother’s milk.

Atypical myopathy (AM) is a frequently fatal, acute muscle disorder, which in Europe is associated with the ingestion of hypoglycin A, a toxin found in the leaves and seeds of trees such as the Acer pseudoplatanus (sycamore).

A report in the Journal of Veterinary Internal Medicine, describes a case of Atypical Myopathy in haflinger foal, who showed signs of depression and weakness six hours after she was born.

Analysis of the foal’s blood revealed increased concentrations of acylcarnitines and MCPA-carnitine characteristic of blood from AM affected horses.

The filly was delivered at full term and in a normal delivery; the foal stood up, suckled colostrum within 2 hours and was evaluated by the owner as clinically normal. “Depression and weakness were observed after about 6 hours; therefore, the veterinarian was called. Because of a suspicion of septicemia, transport to a clinic was recommended to the owner but he refused it for financial reasons,” the authors of the report said.

A Sycamore Maple (Acer pseudoplatanus) in Germany. Photo: Willow (Own work) CC BY-SA 3.0 via Wikimedia Commons
A Sycamore Maple (Acer pseudoplatanus) in Germany. Photo: Willow (Own work) CC BY-SA 3.0 via Wikimedia Commons http://creativecommons.org/licenses/by-sa/3.0

At 12 hours old the filly was unable to stand, and the owner bottle-fed her. But because of further worsening of her clinical condition, the foal was euthanized at 16 hours old.

The question arose as to how the foal became exposed to the toxin.

It transpired that the mare had shown signs of AM in the sixth month of pregnancy, with diagnosis  confirmed by laboratory tests. The mare recovered with treatment. Before foaling the mare had been grazing in a paddock containing sycamore trees, but showed no clinical signs of AM.

The report’s authors suggest two possible explanations: “(a) Hypoglycin A (HGA) or its metabolites accumulated in the mare’s placenta with consequent transfer to the foetus or (b) these compounds were secreted into mare’s milk.”

They continued: “It is known that some toxins or drugs can pass into the colostrum in human. If the colostrum of the mare was contaminated by HGA or its metabolite, it could have intoxicated the foal. However, there is no information about excretion of HGA or its metabolite into milk in the mare or the amount of toxin that is required for AM clinical manifestation in a newborn foal.

Newborn foal with atypical myopathy, Journal of Veterinary Internal Medicine
Radana Karlíková, Jitka Široká, Marek Mech, David Friedecký, Hana Janečková, Lucie Mádrová, Františka Hrdinová, Zuzana Drábková, Olga Dobešová, Tomáš Adam, and Petr Jahn. DOI: 10.1111/jvim.15236 

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