Before modern medicine, tetanus was a scourge of man. This often fatal condition is caused by a nerve toxin produced by a bacterium called Clostridium tetani [claw strid′ ee um tet′ an ee].

The bacteria grow in contaminated wounds, and the resulting toxin causes muscle spasms. Characteristic clenching of the jaw muscles led to the descriptive term lockjaw.

In people, the disease is most common among newborns, the elderly, those with major tissue damage, and IV drug users. Tetanus is fairly rare in companion animals except for horses, which most often become infected from an unrecognized or untreated puncture wound.

Treatment is difficult and not always effective, so prevention is key. All wounds should be thoroughly cleaned to prevent bacterial growth. And tetanus vaccination is highly recommended for mares and foals, followed by yearly boosters.