Equine grass sickness (EGS) is a frequently fatal neurological disease of grazing horses in Europe, causing severe gastrointestinal paralysis and prolonged suffering.
EGS causes intense and prolonged suffering in affected horses. Acute cases present with unrelenting abdominal pain from paralytic ileus — the gut stops moving entirely, causing gas accumulation, distension, and distress that cannot be relieved by analgesia alone. Horses show profuse sweating, muscle trembling, and repeated lying down and rising in response to pain. The distress is severe enough that euthanasia is often the most welfare-appropriate decision in acute cases. Chronic cases that are managed through intensive nursing face months of nasogastric feeding, weight loss, muscle wasting, and reduced quality of life during recovery. The uncertainty of prognosis — some chronic cases recover fully, others deteriorate — makes welfare decision-making particularly difficult.