Tetanus - Horse

Also known as:

Lockjaw

Description

In a pathological context, "tetanus" is an infectious disease caused by the bacterium Clostridium tetani.

• • Physiologically, the term "tetanus" refers to continuous sustained muscle contraction.
    • The disease caused by Clostridium tetani is characterised by this feature.

Signalment

Clostridium tetani generally cause infection via wound contamination. Cuts or deep puncture wounds are most commonly infected. C. tetaniproduces tetanospasmin, a neurotoxin that inhibits the release of the neurotransmitters GABA and glycine from interneurons in the spinal cord and brain. Thi causes increased excitation of the brainstem and motor neurons, leading to unopposed muscle contraction.

• • • The frequency of action potentials at the neuromuscular junctions increases above a threshold.
    • 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
• 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