What is Tetanus? 

Tetanus is neurological disease caused by the bacterium Clostridium tetani. Once established in a wound, Clostridium tetani produces a toxin which causes stimulation of the nervous system. While tetanus can affect humans and other domestic animals, the horse is considered particularly sensitive to tetanus neurotoxins.

Clinical Signs: Signs and symptoms arise from the C. tetani neurotoxin’s ability to block inhibitory signals in the spinal cord, leading to painful muscle spasms and rigidity and include:

  • Stiffness and difficulty ambulating
  • Wide-based “sawhorse” stance
  • Agitation
  • Third eyelid protrusion
  • Trismus (lock jaw)
  • Extended neck
  • Elevated tail
  • Difficulty swallowing
  • Unable or unwilling to eat 
  • Abnormal (decreased or absent) gut sounds
  • Abnormal (decreased or absent) defecation

Diagnosis: A presumptive diagnosis is usually made based on the presence of the classical clinical signs of stiffness, lock jaw, and protrusion of the third eyelid, often in combination with a negative vaccination status and the identification of a wound or other physical entry point. Laboratory techniques can be used to confirm the presence of the bacteria in an infected wound.


  • Elimination of C. tetani as the source of toxin production – wounds should be cleaned and debrided. Initiate treatment with appropriate antibiotics.
  • Neutralization of the circulating, unbound neurotoxin by tetanus antitoxin (TAT). Commercial availability of TAT is variable.
  • Muscle relaxation and pain medications – tetanus is a very painful disease due to widespread muscle spasms. Limiting exposure to stimuli by housing horse in a quiet stall can help prevent painful muscle spasms. 
  • Supportive care to prevent secondary trauma, provide wound care, provide digestive and hydration support for horses unable to eat and drink. Severely affected horses may require additional critical care. 

Prevention: The vaccine against tetanus (tetanus toxoid) is a very successful and highly protective vaccine. Due to the ever-present risk of exposure, the severity of the disease, and the almost 100% protection following vaccination, tetanus toxoid is considered a core equine vaccine and should be included in equine immunization programs for every horse. 

  • It is generally accepted that tetanus toxoid administered per manufacturer recommendations is both safe and efficacious. All tetanus toxoid vaccines are labeled for annual (12 month) revaccination. 
  • Protective responses from vaccination are usually attained within 2 weeks of the second dose.