These days, fortunately, few horses die of botulism and tetanus. One reason why is the availability of two types of products: toxoids, which prevent disease, and antitoxins, which treat it.

Modified bacterial toxin

A toxoid is a modified bacterial toxin treated, typically with formaldehyde or heat, to remove its damaging properties. The botulism toxoid vaccine, for instance, stimulates a horse’s immune system to produce antibodies to the toxins released by Clostridium botulinum spores, neutralizing them and thus preventing disease. The tetanus vaccine is also a toxoid product, as are vaccines that protect people against pertussis and diphtheria. For optimal protection, experts recommend an initial vaccine series, followed by annual boosters.

Preformed antibodies

Unlike toxoids, which stimulate the production of protective antibodies, antitoxin contains preformed antibodies derived from immunized animals.

Antitoxins are therapeutic rather than preventive. If a horse develops botulism, for example, a veterinarian will administer antitoxin to neutralize toxins in the bloodstream. Likewise, a horse with tetanus receives a tetanus antitoxin. An antitoxin can prevent further damage, slowing or halting progression of disease. But it cannot reverse the damage that toxins have already done. Horses treated with antitoxin are also provided supportive care. In addition to botulism and tetanus, antitoxin products can treat snakebite in horses. As with any treatment, antitoxin therapy has risks as well as benefits. Your veterinarian will make a diagnosis before prescribing an antitoxin.

The diseases toxoids and antitoxins fight

Tetanus is a rare but usually fatal poisoning, caused by toxins produced by the Clostridium tetani bacteria. C. tetani
spores, found in soil and manure, breed beneath the skin of a closed wound, releasing neurotoxins into the bloodstream. The toxins attack the nervous system via the spinal cord, resulting in progressive paralysis that can lead to death.

Botulism poisoning is caused by toxins from the bacterium Clostridium botulinum. This condition affects the horse’s nervous system and can be life-threatening. Horses can contract botulism in three ways: by ingesting hay or other feed contaminated with botulinum toxin, by having a wound contaminated with C. botulinum spores or in the case of foals, by having spores germinate in the intestines and produce toxin (Shaker foal syndrome).