Tetanus in horses

Craig Wood, University of Kentucky

Tetanus, also known as lockjaw, is an extremely serious disease of the central nervous system that has a high mortality rate in horses. The bacteria causing tetanus is found worldwide, and therefore, every unvaccinated horse is a potential victim.

The disease is caused by a toxin released by the bacteria Clostridium tetani. This bacteria is normally found in the intestinal tract of horses and is passed in the feces. The spores are always present in the soil in any horse facility. The bacteria is anaerobic, meaning that it multiplies in areas where oxygen is not present. Deep puncture wounds contaminated with dirt are ideal locations for tetanus to flourish.

Tetanus may lie dormant in the animal for as long as six months. Therefore, the onset of signs may be months after the original injury.

Clinical Signs icon


  1. inability to open mouth to eat and drink
  2. eyes wide open and ears rigid
  3. stiffness and rigidity of the entire body
  4. extreme sensitivity to sounds, sights, and touch
  5. third eyelid closes uncontrollably
    (One way to distinguish tetanus from other neurological diseases is to clap your hands and watch the third eyelid. It will close uncontrollably.)
  6. convulsions and death in 75 to 80 percent of cases.


If the horse makes it through the first week, chances of recovery are good, but full recovery may take many months.



Treatment is mainly supportive. The horse should be kept in a dark, quiet place with plenty of padding to prevent injury. Adequate nourishment and fluid intake must be monitored. Sedatives and muscle relaxers should be administered along with the tetanus antitoxin.




Vaccination with tetanus toxoid is a highly effective preventive. It is given in two doses four to eight weeks apart, followed by a booster every year thereafter. Broodmares should be vaccinated four to eight weeks prior to foaling to ensure passive immunity for the foal. The foal may then receive its first injection at 3 months of age because maternal immunity will not interfere with the vaccine.


If an unvaccinated horse is wounded, it should be given the tetanus antitoxin for immediate protection. However, this protection is short-lived, so the horse should be given the toxoid vaccine at the same time and a booster four weeks later.