Tetanus, also referred to as "lockjaw", is a highly fatal disease in horses. The disease is caused by Clostridium tetani, a highly toxic bacterial organism that releases a toxin that affects the horse's nervous system. C. tetani are commonly found in around the barn environment--anywhere horses are kept. This is because the organism naturally inhabits even a healthy horse's bowels and thus, manure.
Since the tetanus bacteria is frequently found within the horse's normal environment, it puts horses at a high risk of developing tetanus if they get hurt. Any open wounds, especially puncture wounds in the foot, provide an open pathway for the bacteria to enter the horse's body and cause tetanus. It is because of this high risk, that horses are routinely vaccinated against tetanus--by receiving the tetanus vaccine or toxoid which contains the inactivated tetanus toxin. Once injected into the horse, within 2-3 weeks, their immune system will develop antibodies to protect themselves against the toxin. The effects of one vaccine will usually protect a horse for about a year, where they will need to be re-vaccinated for the next year, and ongoing.
The incubation period is typically 1 to 3 weeks but can take up to several months.
The severity of the symptoms and rate of the progression of the disease depends on the age and size of the horse and the dose of toxin. Tetanus is expensive to treat and has a high mortality rate; therefore all horses should be actively immunized using tetanus toxoid as part of the core vaccination program.