Hypoglycin A Content in Blood and Urine Discriminates Horses with Atypical Myopathy from Clinically Normal Horses Grazing on the Same Pasture.
Authors: Bochnia M, Ziegler J, Sander J, Uhlig A, Schaefer S, Vollstedt S, Glatter M, Abel S, Recknagel S, Schusser G F, Wensch-Dorendorf M, Zeyner A
Journal: PloS one
Summary
# Atypical Myopathy: Detecting Hypoglycin A Exposure Before Clinical Signs Appear Hypoglycin A (HGA)—a toxic amino acid found in sycamore maple seeds—is established as the causative agent of atypical myopathy in grazing horses, yet most evidence has relied on retrospective seed analysis rather than sampling during active outbreaks. This German investigation strengthened the causal evidence by collecting sycamore seeds, serum and urine samples from affected horses during confirmed disease episodes, plus asymptomatic horses grazing the same contaminated pastures. Blood and urine HGA levels in clinically affected horses were dramatically elevated (serum: 387–8494 μg/L; urine: 144–926 μg/L) compared to controls (<10 μg/L), with toxic metabolites (MCPA-conjugates) proportionally elevated, whilst apparently healthy cograzing horses occupied an intermediate position—showing significantly higher HGA and metabolite concentrations than unexposed controls but substantially lower than diseased individuals. This differential detection capability is clinically valuable: identifying elevated HGA in asymptomatic animals suggests subclinical exposure and potential disease progression, offering a window for prophylactic intervention such as pasture removal before clinical myopathy develops. For practitioners managing at-risk herds during high-risk seasons (spring and autumn), these biomarkers provide an objective diagnostic tool and early warning system that extends beyond clinical observation alone.
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Practical Takeaways
- •Blood and urine HGA testing can identify at-risk horses on contaminated pastures before clinical signs appear, enabling early preventive management.
- •Monitor pastures for Acer spp. seed fall during spring/autumn and consider removing horses from grazing when seeds are present and HGA levels are detectable in healthy animals.
- •Subclinical HGA elevation in clinically normal cograzing horses signals environmental risk and should trigger pasture management intervention even in the absence of overt disease.
Key Findings
- •Serum HGA concentrations in affected horses ranged from 387.8–8493.8 μg/L compared to <10 μg/L in controls, establishing clear biochemical discrimination.
- •Urine HGA concentrations in affected horses (143.8–926.4 μg/L) were similarly elevated versus controls (<10 μg/L), providing a practical diagnostic marker.
- •Clinically healthy cograzing horses showed intermediate HGA levels (serum 108.8 ± 83.76 μg/L, urine 26.9 ± 7.39 μg/L), indicating subclinical exposure and toxin accumulation.
- •Acer pseudoplatanus seeds on affected pastures contained 1.7–319.8 μg HGA/g seed, directly correlating exposure timing with disease outbreak.