Botulism in horses is rare, but is usually fatal. It is caused by toxins produced by the bacteria known scientifically as Clostridium botulinum. The botulism toxins act on the peripheral nervous system by preventing transmission of the nervous impulses. These toxins are found in the soil and in decaying plant or animal matter. Adult horses and foals usually less than 8 months old can be affected.

Foals

1. impaired suckling

2. inability to swallow

3. decreased eyelid and tail tone and dilated pupils

4. respiratory paralysis, which causes death.

Adults

1. many of the same signs seen in foals

2. eventual muscle weakness, tremors, and collapse

3. respiratory paralysis, which causes death.

If botulism is caught early, there is a polyvalent equine antitoxin (an antibody produced in response to a toxin from the bacteria) that is active against several types of the organism. This antitoxin has improved the chances of survival in horses.

A vaccine is available for use and is recommended only for endemic areas.