Equis ISSN 2398-2977

Clostridium tetani

Synonym(s): C. tetani

Contributor(s): Susan Dawson, Richard Walker

Introduction

Classification

Taxonomy

  • Family:Bacillaceae.
  • Genus:Clostridium.
  • Species:tetani.

Etymology

  • Gk:kloster- spindle;
  • tetanos- tension/muscular spasm.

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Clinical Effects

Epidemiology

Habitat

  • Widely distributed in soil.
  • Transiently in intestinal tract, especially horses.
  • The spores ofC. tetaniare widely distributed in soil.

Lifecycle

  • Spores germinate in an anaerobic environment, such as devitalized tissue.
  • Proliferation of the bacterium results in neurotoxin production.

Transmission

  • Spores introduced into wounds from soil.

Pathological effects

  • Acquired resistance depends on circulating antitoxin.
  • Surviving animals are susceptible to reinfection.
  • Horses relatively susceptible to tetanus   Tetanus  .
  • Dogs, and even more so cats, relatively resistant to tetanus.
  • The endospores enter wounds or trauma sites (eg through the umbilicus, or after castration   Testis: castration - post-operative complications  , or into the uterus after dystocia).
  • Anaerobic conditions are provided by the presence of facultative anaerobes and the spores germinate in devitalized tissues.
  • The cells multiply and produce 2 exotoxins: tetanolysin (a hemolysin), which is apparently insignificant, and the neurotoxic tetanospasmin.
    Descending tetanus
  • Typical of horses.
  • Tetanospasmin disseminated in bloodstream   →   remote areas   →   toxin enters CNS at many levels   →   generalized tetanus, often beginning cranially.
    Ascending tetanus
  • Especially in carnivores.
  • Tetanospasmin travels along the peripheral nerves   →   binds to specific gangliosides of the motor nerve terminals   →   suppresses release of afferent inhibitory neurotransmitters eg, glycine   →   spastic paralysis and characteristic spasms.

Other Host Effects

  • Transient in the intestinal tract. Commensals unless they gain access to wounds or traumatized tissue.

Control

Control via animal

Control via chemotherapies

Vaccination

  • Tetanus toxoid vaccines available   Tetanus toxoid  .
  • Should be given to horses annually after primary course of two doses 1-2 months apart.

Other countermeasures

  • Prompt administration of antitoxin (10,000 to 300,000 units for horses)   Tetanus antitoxin  - but not into CNS.
  • Supportive treatment: sedatives   Anesthesia: standing chemical restraint  and muscle relaxants.
  • Nursing care.
  • Some have suggested intra-thecal administration of antitoxin to horses, but this is not currently recommended.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent reference from PubMed and VetMedResource.
  • Wilkins C A, Richter M B, Hobbs W B, Whitcomb M, Bergh N & Carstens J (1988) Occurrence of Clostridium tetani in soil and horses. S Afr Med J 73 (12), 718-720 PubMed.

Other sources of information

  • Biberstein E L (1990) The Clostridia. In: Review of Veterinary Microbiology. Eds: E L Biberstein & Y C Zee. Blackwell Scientific. pp. 306-309. ISBN 0 86542 085 8.

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