Outbreaks of equine grass sickness in Hungary.
Authors: Schwarz B, Brunthaler R, Hahn C, van den Hoven R
Journal: The Veterinary record
Summary
# Editorial Summary: Equine Grass Sickness Outbreaks in Hungary Equine grass sickness (EGS) remains predominantly a British condition, yet a Hungarian stud experienced devastating outbreaks in 2009–2011 after nearly a decade of freedom from the disease, with mortality striking 11 of 60 yearling to three-year-old colts in the initial outbreak and a further four acute cases following winter pasture exposure. Clinical presentation in the Hungarian cases differed somewhat from typical British EGS presentations, though histopathological examination confirmed the diagnosis; toxicological analysis of affected animals revealed the presence of carbofuran (a carbamate pesticide) in liver tissue across most cases examined. The authors hypothesise that carbofuran exposure may compromise immune function and thereby predispose horses to EGS, a mechanism warranting urgent investigation given that carbamates are known to cause delayed neurotoxic effects in humans. For practitioners, this work suggests that pesticide contamination—particularly carbamate residues in forage or pasture—warrants consideration as a potential risk factor in EGS cases, particularly in regions where such compounds remain in use, and highlights the need for further research to establish causative versus incidental associations between environmental toxin exposure and disease susceptibility.
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Practical Takeaways
- •EGS is not confined to Great Britain and should be considered in differential diagnoses for European studs with unexplained acute neurological disease and mortality in young horses
- •Environmental exposure to carbamate pesticides may be a risk factor for EGS; investigate grazing field pesticide history when clusters of EGS cases occur
- •Clinical presentation of EGS may vary geographically; maintain awareness of regional variations in disease manifestation when consulting diagnostic guidelines
Key Findings
- •An EGS outbreak occurred in Hungary affecting 11 of 60 horses in 2009/10 and 5 of 12 one- to three-year-old colts, with 4 additional acute cases following winter field exposure in 2010/11
- •Affected Hungarian horses displayed somewhat different clinical signs compared to previously reported Great Britain cases
- •Carbofuran, a carbamate pesticide, was detected in liver tissue in most examined cases
- •Carbofuran may predispose horses to EGS development through immune system effects, suggesting a potential environmental toxicological cofactor in disease pathogenesis