Equine grass sickness in Scotland: a case-control study of signalment- and meteorology-related risk factors.
Authors: Wylie C E, Shaw D J, Fordyce F M, Lilly A, McGorum B C
Journal: Equine veterinary journal
Summary
# Editorial Summary: Equine Grass Sickness Risk Factors in Scotland Equine grass sickness remains a devastating condition with high mortality rates in Britain, yet previous research into its risk factors has produced inconsistent findings. Wylie and colleagues conducted a retrospective case-control analysis of 455 EGS cases matched against 910 controls treated at the Royal (Dick) School of Veterinary Studies between 1990–2006, examining signalment variables and meteorological data from multiple time windows preceding disease onset. Native Scottish pure breeds emerged as significantly higher-risk animals (3.56 times more likely to develop EGS than crossbreeds), whilst older horses aged 11–20 years showed substantially lower risk than their 2–10 year-old counterparts, and stallions were notably protected compared with mares. Geographical latitude within Scotland also influenced risk, with more northerly locations associated with increased incidence; weather patterns mattered too, with increased sun exposure and frost days elevating EGS risk, whilst higher maximum temperatures were protective. These findings offer practical value for at-risk premises—owners and managers can now identify vulnerable animals and geographical hotspots to implement preventative management strategies, whilst the meteorological associations may guide future aetiological investigations into this poorly understood condition.
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Practical Takeaways
- •Owners of native Scottish breeds and younger horses (2–10 years) should implement enhanced management strategies to reduce EGS risk, particularly in northern Scotland
- •Monitor environmental conditions during periods of increased sunshine and frost, as these weather patterns are associated with higher EGS incidence
- •Older horses (11+ years) and stallions show lower EGS susceptibility and may require different risk management priorities than younger or female animals
Key Findings
- •Native Scottish pure breeds had 3.56-fold increased risk of EGS compared to crossbreeds (95% CI 2.43–5.43)
- •Animals aged 11–20 years had 68% reduced risk compared to 2–10 year-olds (OR = 0.32, 95% CI 0.22–0.45)
- •Northern geographic location within Scotland associated with increased EGS risk (OR = 1.08 per unit northing, 95% CI 1.06–1.10)
- •Increased sun hours (OR > 1.43) and frost days (OR > 1.13) were meteorological risk factors; higher maximum temperatures were protective (OR < 0.83)