Equine Grass Sickness: A Devastating Welfare Condition

Equine grass sickness is a devastating and often fatal condition affecting the autonomic nervous system of horses, causing intense suffering and high mortality.

Key Facts

Equine grass sickness is caused by the soil bacterium Clostridium botulinum type C in some theories but remains incompletely understood
Clinical signs range from mild dysphagia and depression in chronic cases to acute death within 24-48 hours
Acute grass sickness is invariably fatal; chronic cases sometimes survive with intensive nursing
The disease primarily affects grazing horses, particularly on pastures with Clostridium-supporting soil conditions
Surviving chronic cases require months of intensive nursing including hand-feeding

Welfare Considerations

Grass sickness causes intense suffering across its clinical spectrum. Acute cases develop severe colic pain, profuse sweating, muscle tremors, and difficulty swallowing before rapid death — a profoundly distressing final illness. Subacute cases develop over days with abdominal pain, inability to swallow, and progressive debilitation. Even chronic cases that have a survival chance face months of profound weakness, weight loss, and difficulty eating before potential recovery. The decision to attempt treatment versus humane euthanasia in chronic cases requires honest assessment of the severity of ongoing suffering against the probability of recovery. Many affected horses that reach the chronic stage still die or are euthanised during recovery due to complications.

What You Can Do

Contact your veterinarian immediately if your horse shows signs of grass sickness including depression and dysphagia
Discuss honestly with your vet whether treatment or euthanasia provides the best welfare outcome for your horse
Support Equine Grass Sickness Fund research into the causes and prevention of this devastating condition
Be aware of pasture-level risk factors and consider rotational grazing management in high-risk areas