Tetanus, or "lockjaw", is an acute, often fatal disease caused by the bacteria found in soil. Tetanus is caused by Clostridium tetani bacteria that affects animals and humans. Infection most commonly occurs after an injury, but may also develop after surgical operation. The bacteria produce the toxin tetanospasmin which affects the Central Nervous System. Different animals have different level of susceptibility to this bacteria. Clostridium tetani spores are also commonly found in the feces of domestic animals, especially those of horses, and in soil contaminated by the feces. Clostridium tetani spores may stay in soil for many years and are resistant to many standard disinfection processes, including steam heat (100º C for 15 minutes).
Although all species of domestic animals are susceptible to tetanus, horses are most sensitive to tetanus toxin. If the germ enters a deep wound and the wound closes too soon, the horse may easily contract the infection through his blood stream. A horse that receives a bad wound, particularly if there is known to be tetanus in the area, should at once receive the anti-tetanus vaccine which will prevent the disease.
The earliest symptom of tetanus is extreme sensitivity. Within 10 to 14 days following injury, horses become increasingly nervous. They jump violently on being touched. Some seem unwilling to be handled and may respond with aggression. Protrusion of the third eyelid, and stiff gait are the most common clinical signs. Spasms of the masseter muscles--muscles that bring the upper jaw and lower jaw together--occur early in the disease which results in "lockjaw". Loud noises, colic, and sweating usually appear at a later stage of the disease.
Treatment usually consists of administration of antibiotics, tranquilizers, tetanus toxoid, and antitoxin. Persistent treatment and much nursing care are needed. Affected horses need to be protected from light and sound that can stimulate nervousness. Horses are placed in darkened stalls and their ears are plugged with cotton. Antitoxins, antibiotics and sedatives are usually administered for several weeks. If the animal has been vaccinated prior to the injury, responds to the tranquilizers, the prognosis is usually good. Prevention is twofold. Unvaccinated horses usually receive tetanus antitoxin with 24 hours following injury or surgery. This provide temporary protection for 10 to 14 days. If healing is not complete by that time, vaccination is repeated. No horse should live its life without being immunized with tetanus toxoid which provides a very stable immunity. Annual boosters and vaccinations following injury or surgery provide good protection against tetanus.