But botulism is also a danger to horses, and cases are on the rise. Most horse owners are familiar with tetanus and understand that the tetanus organisms are always in the environment. A preventive vaccination is essential. Similar to the tetanus infection, botulism is much more lethal. It is one of the most potent toxins known, and small amounts can be deadly to animals and humans.
Horses are particularly susceptible.
Dead rodents or other animals have been known to be incorporated into hay bales. The decaying matter releases the botulism toxin and the horse ingests it when he eats or drinks. The first sign of botulism may be difficulty in closing the eyelids or in swallowing. Horses stand with their muzzles in the food or water bucket because they are hungry but cannot swallow. The animal may tremble, lie down more than usual and may exhibit poor or weak tail and tongue tone.