What is Lockjaw (Tetanus) in Horses? Should You Vaccinate?

Lockjaw, or Tetanus, is a severe and often fatal disease affecting horses, caused by the bacterium Clostridium tetani, which is commonly found in soil, manure, and dust. Despite its prevalence in the environment, vaccination rates remain worryingly low in the UK, putting many horses at risk. Responsible horse owners understand that vaccination not only protects individual horses but also helps prevent outbreaks in the wider equine community.

In the UK, tetanus vaccination is typically included in the biannual equine influenza vaccination routine, but some horses might not be receiving this crucial protection. Ensuring your horse is vaccinated against Lockjaw is a vital part of responsible equine care and disease prevention.

What is Lockjaw?

Lockjaw refers to the symptoms caused by tetanus infection, characterised by muscle rigidity and spasms that often lead the horse’s jaw to lock shut, making eating and drinking impossible. The official term for Lockjaw is Tetanus, a disease that attacks the central nervous system. Similar to humans who receive life-long anti-tetanus vaccinations, horses require vaccination to prevent this distressing and fatal condition.

Causes of Lockjaw

Tetanus is caused by toxins released by Clostridium tetani, an anaerobic bacterium thriving in environments devoid of oxygen, such as deep wounds. It commonly enters a horse’s body through even minor cuts or puncture wounds sustained in fields or stables. Because the bacterium is robust—resistant to heat, drying, and many chemicals—it can survive in the environment for years, waiting to infect a susceptible host.

Recognising the Signs and Symptoms

Early signs of tetanus can be subtle, especially since minor wounds can be missed, particularly in horses with thick winter coats. Look for one or more of the following warning symptoms:

• An anxious or distressed expression, possibly with flared nostrils and eyelid retraction due to muscle spasms
• Difficulty or inability to open the mouth fully, causing problems eating and drinking
• A stiff or raised tail tip
• Dropping partially chewed food (‘quidding’) and increased drooling due to swallowing difficulties
• Ears positioned rigidly as if fixed on an object
• Heightened sensitivity to sounds and touch
• Stiff, uncoordinated movements or gait changes without other causes
• Prolapse of the third eyelid partially covering the eye
• Signs of colic

Understanding Clostridium tetani

This bacterium is widespread on farms, especially in soils enriched with horse and cattle manure. It was first identified in the late 19th century and continues to be a significant health concern. The bacterium’s anaerobic nature allows it to thrive in deep, oxygen-poor wounds where it releases tetanospasmin toxin that disrupts nerve function, leading to the classic Lockjaw symptoms.

Treatment Options for Tetanus

Tetanus treatment is challenging and usually depends on the stage and severity of the disease at diagnosis. It involves intensive supportive care including:

• Identifying and cleaning the wound site with antibiotics where possible
• Administering antitoxin in early diagnosed cases to neutralise circulating toxins, though it cannot counteract toxin already bound to nerves
• Using sedatives and muscle relaxants to ease painful spasms
• Providing a calm, dark, and quiet environment with minimal disturbance
• Using cotton wool in ears to block out noise that may trigger spasms
• Hydrating and feeding compromised horses via intravenous fluids and nasogastric tubes if necessary

Despite treatment, mortality rates range from 50% to 75%, emphasising the importance of prevention. Survivors require prolonged and dedicated nursing care.

Vaccination: The Best Defence Against Lockjaw

The 2025 UK veterinary consensus strongly advocates for routine tetanus vaccination as a critical preventative measure. The typical protocol involves:

1. Primary vaccination course: Two doses 4 to 6 weeks apart, usually starting when horses are over 5-6 months old.
2. First booster: Given 12 to 17 months after the primary course to solidify immunity.
3. Subsequent boosters: Administered every two years thereafter for healthy, low-risk horses.

Foals receive initial protection through maternal antibodies in colostrum. However, if mares are not vaccinated, veterinarians recommend administering antitoxin at birth and an accelerated vaccination schedule. For unvaccinated or lapsed horses with wounds, immediate antitoxin is crucial as it provides rapid short-term protection while vaccination immunity develops.

Tetanus vaccines are often combined with equine influenza vaccines for convenience and to improve compliance. Regular vaccination has dramatically reduced the occurrence of Lockjaw since its introduction, making today’s cases rarer but no less deadly without protection.

Responsible Horse Ownership and Next Steps

Ensuring your horse is vaccinated against tetanus is one of the most responsible and impactful actions you can take to safeguard its health. Consult your vet to tailor a vaccination plan suitable for your horse’s age, health status, and lifestyle. Regular boosters and prompt wound care are key to preventing this heartbreaking disease.