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Tetanus

pequis

Synonym(s): Lockjaw, Sawhorse stance


Introduction

  • Tetanus is characterized by tetany, hyperesthesia and seizures; horses are highly susceptible.
  • Cause: three exotoxins of Clostridium tetani Clostridium tetani.
  • Signs: hyperesthesia and tonic spasm of muscle groups.
  • Diagnosis: history and clinical signs.
  • Treatment: antibiotics, antitoxin, supportive therapy.
  • Prognosis: very guarded.
Print off the Owner factsheet Tetanus - 'lockjaw' to give to your clients.

Pathogenesis

Etiology

  • Clostridium tetani Clostridium tetani: gram-positive, strictly anaerobic bacillus with terminal spore Clostridium tetani.
  • Produces a protein exotoxin of 67,000 molecular weight with 3 components:
    • Tetanospasmin.
    • Tetanolysin.
    • Non-spasmogenic toxin.
  • Horses are sensitive to all of the components, but the clinical signs of tetanus are mainly due to tetanospasmin.

Predisposing factors

General

  • Puncture wound contaminated with soil/spores.
  • Contamination of uterus at parturition.

Specific

  • Anerobic tissue environment.

Pathophysiology

  • Spores of C. tetani Clostridium tetani → three exotoxins produced (tetanospasmin, tetanolysin and non-spasmogenic toxin) → CNS → muscle spasms.
  • Spores from C. tetani carried into puncture wounds, uterus or umbilicus → germinate in anerobic tissue conditions → toxin production → toxin travels along peripheral nerves → CNS.
  • Tetanospasmin binds to gangliosides in the CNS → inhibition of cholinesterase and prevention of release of inhibitory transmitter, glycine → abolition of synaptic inhibition of spinal motor neurones (GABA) → accumulation of acetylcholine → continued stimulation of neurones in motor and reflex arcs.
  • Tetanospasmin also causes inhibition of protein synthesis.
  • Tetanolysin causes tissue damage and necrosis at site of infection.
  • Non-spasmogenic toxin may block transmission in peripheral neuromuscular junctions.

Timecourse

  • Incubation period 7-21 days (possibly much longer, up to 2 months).
  • Death may follow onset of clinical signs in 5-10 days (3 days in foals).

Epidemiology

  • C. tetani spores are ubiquitous in soil and intestinal contents of horses.
  • Clinical disease occurs sporadically.
  • Infection occurs via a puncture wound, the umbilicus, or contamination of uterine contents during parturition.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Fisher R J (2005) The treatment of tetanus in horses using intrathecal injection of tetanus antitoxin. UK Vet 10 (6), 12-14.
  • Steinman A, Haik R, Elad D & Sutton G A (2000) Intrathecal administration of tetanus antitoxin to three cases of tetanus in horses. Equine Vet J 12 (5), 237-240 VetMedResource.
  • Sedrich S A, Seahorn T L & Martin G (1996) What is your neurologic diagnosis? Tetanus. JAVMA 209 (1), 57-58 PubMed.
  • Abrutyn E & Berlin J A (1991) Intrathecal therapy in tetanus. A meta-analysis. JAVMA 266 (16), 2262-2267 PubMed.
  • Wilkins C A, Richter M B, Hobbs W B et al (1988) Occurrence of Clostridium tetani in soil and horses. S Afr Med J 73 (12), 718-720 PubMed.

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