Equine Grass Sickness (EGS), often called "Equine Dysautonomia", is a rare but predominantly fatal illness in horses, ponies and donkeys that affects the autonomic nervous system. The majority of visible clinical signs are related to paralysis within the digestive tract although nerve damage occurs throughout the body. Visible symptoms include colic, difficulty in swallowing, drooling, muscle tremors, rapid weight loss and behavioral abnormalities. The disease primarily affects animals between the age of two and seven years that are pasture-grazed.
Many scientific studies on the causes of EGS have been carried out, but mostly the causative agents of the disease have remained speculative. However, it has been widely believed that the disease is linked to elements of the animals’ food or drinking water, including the possibility that a kind of bacteria called cyanobacteria present in drinking water could be the cause. Now that speculation has been given credence with a new study, titled "Edaphic and phytochemical factors as predictors of equine grass sickness cases in the UK", published in the Frontiers in Pharmacology journal. The research, carried out by the The School of Pharmacy at the University of London, implicates previously unknown triggers in EGS.
The research team analysed soil, plant, and water samples from a total of 23 EGS sites and 11 control sites. They found significantly higher levels of iron and heavy metals in herbage growing in EGS sites, in addition to an abundance of toxic buttercups. The report also indicated that cyanobacteria in the drinking water are unlikely to be a factor as they were absent in the samples analyzed. The findings suggest that the presence of toxic buttercups and higher than normal levels of heavy metals in the soil could predict potential cases of EGS.