Horse Botulism: Prevention and Emergency Management

Botulism causes progressive and often fatal paralysis in horses, with vaccination and careful forage management being the primary welfare interventions in susceptible populations.

Key Facts

Botulism in horses is caused by toxins produced by Clostridium botulinum bacteria found in contaminated forage
Haylage and big bale silage are high-risk feeds if prepared or stored incorrectly, allowing bacterial growth
Clinical signs progress rapidly from difficulty swallowing and muscle weakness to recumbency and respiratory failure
Without treatment, mortality rates approach 90% in horses; with supportive care and antitoxin, survival improves
Antitoxin is available but expensive and must be administered early to be effective
Vaccination is available and recommended in endemic areas, particularly the eastern United States

Welfare Considerations

Botulism causes one of the most severe welfare emergencies in equine medicine. Affected horses experience progressive inability to eat, drink, or stand, culminating in respiratory failure. The disease course is rapid, leaving little time for effective intervention. Horses in the later stages of botulism experience extreme distress from inability to perform basic functions. Prevention through vaccination and careful forage management is the highest-welfare approach, as treatment is often insufficient to prevent death.

What You Can Do

Vaccinate horses annually against botulism if you live in endemic areas or feed haylage
Inspect haylage and silage carefully before feeding and discard any bales with damaged wrapping
Never feed haylage with visible mold, bad odor, or low pH failure to horses
Contact your vet immediately if a horse shows weakness, drooling, or difficulty swallowing
Maintain appropriate pH monitoring when producing home-made forage to prevent C. botulinum growth