Tetanus in Horses

Tetanus is uncommon, as the tetanus vaccine is widely used and very effective.

Horses that develop tetanus require immediate veterinary attention, as it is fatal in up to 75% of cases without treatment.

Horses that are treated promptly for tetanus and do not develop secondary complications typically have a fair prognosis.

Other more severe symptoms that are associated with a poorer prognosis of disease include:

• Recumbency (inability to stand)
• Dysphagia (difficulty swallowing)

Secondary to dysphagia, horses are at a higher risk of developing aspiration pneumonia, a serious complication with a poor prognosis. Death is a possible outcome if treatment for tetanus is not pursued.

The severity of symptoms depends on the amount of toxin that enters the body. Rarely, in severe cases when a large amount of toxin is absorbed, the respiratory and heart muscles can be affected, leading to respiratory failure, heart arrhythmias, and sudden death.

Tetanus is caused by a neurotoxin that is produced by the bacterium Clostridium tetani. Spores of this bacterium are commonly found in the soil. Following contamination of an open wound, the bacterium produces this potent neurotoxin that travels to the nerves and causes all of the muscles in the body to be in a contracted, or “spastic,” state.

Horses often develop tetanus through contamination of an open wound or injury. Rarely, surgical or castration sites, injection sites, and foal umbilical stumps can become contaminated and result in the same symptoms.

Symptoms of tetanus typically develop within 1-3 weeks after initial exposure to C. tetani.

Typically, no specific tests are required to diagnose tetanus, other than a history and physical examination.

The hallmark treatment for tetanus is administration of tetanus antitoxin. Other treatments include supportive care such as sedatives, muscle relaxers, minimizing handling, fluid therapy, nasogastric tubing, and physical support.

Horses may require manual evacuation of the rectum or urinary catheterization for waste elimination. Antibiotics may also be warranted to treat infection of the site of injury. If respiratory difficulties arise, horses may require a tracheostomy (temporary hole in the trachea to facilitate breathing).

Other more intensive treatment/management is required if aspiration pneumonia develops as a secondary complication.

Horses that receive treatment quickly after symptoms arise have a favorable prognosis, with full recovery taking up to 6 weeks.

Horses that become recumbent or develop aspiration pneumonia during disease progression have a poorer prognosis, and have a longer road to recovery. The outcome for these cases ultimately depends on their response to treatment, but many cases are euthanized due to management difficulties, costs, and quality of life concerns.

Vaccination is imperative in preventing tetanus. Annual vaccination is recommended for all foals and adult horses (including broodmares). Boosters are recommended after injury if a tetanus vaccination has not been given in the past 6 months.

Although all mammals, including humans, are susceptible to tetanus, it is not contagious. Horses are more susceptible to tetanus compared to some other species, which is why regular vaccination against tetanus is recommended.

Tetanus is not common as most horses are regularly vaccinated.

• Tetanus antitoxin
• Supportive care
• Antibiotics