Tetanus - Horse

Also known as:

Lockjaw

Description

Tetanus is an infectious disease caused by the neurotoxin of the gram-positive bacterium Clostridium tetani. It is a highly fatal disease resulting in spastic paralysis in affected animals. Clostridium tetani causes infection via wound contamination and deposition of bacterial spores in tissue under anaerobic conditions. Cuts, deep puncture wounds, surgical sites may all provide sites of entry for infective spores. C. tetaniproduces tetanospasmin, a neurotoxin that is transferred to distant sites via the vascular system. This causes inhibition of the release of GABA and glycine from interneurons in the spinal cord and brain. This causes increased excitation of the brainstem and motor neurons, leading to unopposed muscle contraction.

Signalment

All domestic species may be affected but foals may be particularly susceptible due to infection through the umbilicus.

• • • Above this threshold, muscle fibres enter a state of tetanus.
      • Muscle spasm is initially present in the muscles of the jaw.
      • This is followed by a difficulty in swallowing.
      • General muscle stiffness and spasms then develop in other parts of the body.
  • Other effects may include:
    • Seizures
    • Effects on the autonomic nervous system

Diagnosis

Clinical Signs

• Diagnosis is made by taking into account the animal's:
  • History
  • Clinical signs

Clinical signs relate to

• Very rarely a wound where the bacteria may have entered may be seen.

Treatment

• Wound debridement
  • Surgical removal of dead and infected tissue from the wound.
• Antibiotic treatment.
  • Metronidazole
    • Treatment with metronidazole decreases the number of bacteria but has no effect on the bacterial toxin.
    • Metronidazole is particularly active against anaerobic bacteria, and so is a good choice for use against C. tetani
  • Penicillin
    • Penicillin is becoming a less favoured treatment for tetanus, since there is a theoretical risk of increased spasms.
• Muscle relaxants
  • Diazepam
  • Midazolam
• Supportive therapy, for example:
  • Administering fluids
  • Providing appropriate nutrition
  • Maintaining a quiet environment with dimmed light.
• Remission take several weeks to months