Bit & Bridle

Equine Tetanus (Lockjaw)

Other Names

  • Lockjaw
  • Clostridium tetani infection

What is Tetanus in Horses?

Tetanus is a non-contagious but potentially fatal neurological disease caused by a potent neurotoxin produced by the bacterium Clostridium tetani. Horses are among the most susceptible of all domestic animals to tetanus — they are estimated to be 10 times more susceptible than cattle — and the mortality rate in affected horses is high, even with intensive treatment.

The good news is that tetanus is almost entirely preventable through vaccination, which is why it is classified as a core equine vaccine. Any unvaccinated or inadequately vaccinated horse that sustains a wound is at genuine risk, and the disease progresses rapidly once signs appear.

What Causes Tetanus in Horses?

Clostridium tetani is an anaerobic, spore-forming bacterium found widely in soil, dust, and the digestive tracts of many animals, including horses. Its spores are extraordinarily resilient and can survive in pastures and stable environments for years.

Disease occurs when spores enter a wound — particularly deep, narrow puncture wounds that create the anaerobic (oxygen-free) conditions in which the bacteria thrive. Once germinated, the bacteria produce two toxins:

  • Tetanospasmin: The primary neurotoxin, responsible for all the clinical signs of tetanus. It travels up peripheral nerves to the central nervous system, where it irreversibly blocks the release of inhibitory neurotransmitters (GABA and glycine). The result is continuous, uncontrolled muscle stimulation — producing the characteristic muscle rigidity and spasms.
  • Tetanolysin: A haemolysin that contributes to local tissue destruction around the wound.

Common Wound Sources

  • Nail or wire puncture wounds — particularly to the foot (a classic and common source)
  • Deep lacerations contaminated with soil or faecal material
  • Wounds that have been packed or bandaged improperly, trapping bacteria in an oxygen-free environment
  • Castration wounds, surgical sites, and injection sites in unvaccinated horses
  • Umbilical cord stump in foals (neonatal tetanus)

Signs and Symptoms of Tetanus in Horses

The incubation period ranges from 3 days to several weeks after infection. Once neurotoxin reaches the spinal cord and brainstem, signs progress rapidly. Early recognition is critical.

Early Signs

  • Stiffness and reluctance to move — often the first sign, may be attributed to other musculoskeletal causes
  • Difficulty chewing or swallowing — caused by masseter muscle rigidity, which gives the disease its common name “lockjaw”
  • A stilted, sawhorse-like stance with all four limbs extended rigidly
  • Raised tail head
  • Flared nostrils and elevated upper lip due to facial muscle spasm

Progressive Signs

  • Prolapse of the third eyelid: One of the most characteristic signs in horses — the nictitating membrane (third eyelid) prolapses across the eye, particularly when startled or when the horse is stimulated. This is an almost pathognomonic sign of tetanus in equids.
  • Muscle spasms triggered by stimuli: Noise, light, touch, or sudden movement provoke generalised tetanic spasms that are extremely painful and exhausting for the horse.
  • Difficulty opening the mouth: The horse cannot eat or drink adequately due to jaw muscle rigidity.
  • Sweating: Profuse sweating is common, related to sympathetic nervous system overactivation.
  • Increased heart and respiratory rate

Terminal Signs

  • Inability to stand
  • Respiratory failure caused by spasm of the chest and diaphragm muscles
  • Death — mortality in untreated cases approaches 80%, and even with treatment remains around 50% in severe cases

Diagnosis

Tetanus is primarily a clinical diagnosis based on the characteristic signs, particularly in the context of a recent wound or procedure. There is no rapid bedside blood test to confirm the diagnosis. The treating vet will look for:

  • The classic “sawhorse” posture
  • Third eyelid prolapse on stimulation
  • Muscle rigidity and spasm
  • History of a wound, surgery, or inadequate vaccination

Laboratory confirmation (culture or toxin detection from the wound) is possible but unreliable and not routinely required for treatment decisions.

Treatment

Treatment of tetanus must begin as soon as possible. Even with intensive care, the prognosis is guarded. Treatment aims to:

Neutralise the Toxin

  • Tetanus antitoxin (TAT): Administered intravenously and ideally also intrathecally (into the spinal canal) to neutralise circulating toxin before it reaches the central nervous system. Note that TAT cannot reverse toxin already bound to neural tissue — it only prevents further binding. Early administration is therefore critical.
  • Human tetanus immunoglobulin (TIG): Sometimes used when equine TAT is not available.

Eliminate the Bacteria

  • Antibiotics: High-dose penicillin (procaine penicillin or potassium penicillin IV) or metronidazole to kill C. tetani at the wound site and prevent further toxin production.
  • Wound management: Thorough debridement of the primary wound site to create aerobic conditions. Hydrogen peroxide may be used to introduce oxygen into deep wounds.

Manage Muscle Spasms

  • Acepromazine and diazepam: To reduce spasm and sensitivity to stimuli.
  • Muscle relaxants: Methocarbamol may be used.
  • Guaifenesin: A central-acting muscle relaxant used in severe cases.

Supportive Care

  • Dark, quiet environment to minimise stimulation — noise and light trigger painful spasms
  • Deep, soft bedding with padded walls if possible to protect a horse that may fall or spasm violently
  • Intravenous fluids and nutritional support (naso-oesophageal tube feeding if the horse cannot swallow)
  • Bladder management (catheterisation) if urinary retention develops
  • Regular turning of recumbent horses to prevent pressure sores and hypostatic pneumonia
  • Intensive monitoring — tetanus cases require around-the-clock care

Recovery, when it occurs, is slow — weeks to months. The horse must be rehabilitated gradually as spasms reduce and normal muscle function returns.

Prevention — Vaccination is the Answer

Tetanus vaccination is one of the most cost-effective and important things any horse owner can do. The tetanus toxoid vaccine is highly effective, safe, and widely available. It is classified as a core vaccine by the British Equine Veterinary Association (BEVA) — meaning it is recommended for all horses regardless of circumstances.

Standard UK vaccination protocol:

  • Primary course: two doses 4–6 weeks apart
  • First booster: 12 months after the second primary dose
  • Subsequent boosters: every 2 years (some manufacturers recommend annually — follow your product’s data sheet)

Combination vaccines (such as Proteqflu-Te combining equine influenza and tetanus) are widely used and convenient. A vaccine must be given at least two weeks before any surgical procedure if the horse’s vaccination status is uncertain.

Unvaccinated horses that sustain a wound should receive tetanus antitoxin (TAT) immediately as emergency prophylaxis, alongside starting a primary vaccination course.

When to Call the Vet

Call your vet immediately — this is an emergency — if:

  • An unvaccinated or inadequately vaccinated horse sustains any deep wound, especially a nail puncture to the foot
  • A horse shows any combination of stiffness, jaw rigidity, elevated tail head, or third eyelid prolapse
  • A horse looks unusually stiff after a recent wound, particularly if the wound was deep or narrow
  • A neonatal foal shows muscle stiffness or inability to suckle in the first few weeks of life

Do not wait. Tetanus progresses rapidly and every hour before treatment begins reduces the chance of a positive outcome.

Frequently Asked Questions About Tetanus in Horses

How effective is tetanus vaccination in horses?

Tetanus vaccination is highly effective. Correctly vaccinated horses are very well protected — published case series consistently show that tetanus in horses is almost exclusively a disease of unvaccinated or inadequately vaccinated animals. The vaccine is safe, inexpensive, and provides excellent long-term protection. There is no good reason for any horse to remain unvaccinated.

Can horses get tetanus more than once?

Surviving natural tetanus infection does not reliably confer protective immunity — the toxin dose causing disease may be insufficient to trigger a full immune response. Horses that recover from tetanus should be vaccinated immediately on recovery to ensure future protection.

My horse stepped on a nail — should I worry about tetanus?

If your horse is current on tetanus vaccination, the risk is very low. If you are uncertain about vaccination status, or the horse has not been vaccinated or is overdue for a booster, call your vet immediately. The vet may administer tetanus antitoxin as emergency prophylaxis while starting or renewing the vaccination course.

How long does recovery from tetanus take?

Horses that survive tetanus have a very long recovery road. Mild cases may recover within 4–8 weeks. Severe cases may take 3–6 months, with a gradual reduction in muscle rigidity and spasm. Some horses retain long-term effects including reduced flexibility or altered gait. Intensive supportive care throughout this period is required.