Equine grass sickness: are we any nearer to answers on cause and prevention after a century of research?

Equine grass sickness (EGS) remains a debilitating and frequently fatal neurodegenerative disease of horses. Although the disease was first recognised in the early 1900s, the definitive cause still remains to be elucidated. A peer-reviewed survey by Mellor et al. (2001) ranked EGS as the most important disease of horses within Scotland and northern England, suggesting that research priorities should focus on identifying a cause and ideally a prevention for this significant disease. This scientific overview reviews the main developments in EGS research in the past 100 years since the disease was first recognised, as they relate specifically to determining the cause of EGS, and concludes by considering a proposed field trial of a preventive Clostridium botulinum (C. botulinum) toxoid that is currently being developed by the authors. In this issue of Equine Veterinary Journal (pp 494-499), Waggett et al. (2010) investigate the prevalence of Clostridium perfringens in faeces and ileal contents from grass sickness.