Introduction

Classification

Taxonomy

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

Etymology

• Gk: kloster - spindle.
• Gr: tetanos - tension.

Active Forms

Resting Forms

Clinical Effects

Epidemiology

Habitat

• The spores of C. tetani are widely distributed in soil.
• Often transiently present in the gastrointestinal tract of animals.

Lifecycle

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

Transmission

• From soil.
• Spores are introduced into wounds from soil.

Pathological effects

• Acquired resistance depends on circulating antitoxin.
• Surviving animals are susceptible to reinfection.

• Dogs, and even more so cats, relatively resistant to tetanus Tetanus.
• The endospores enter wounds or trauma sites, eg through the umbilicus, or after castration Castration , or into the uterus after dystocia Dystocia.
• Anaerobic conditions are provided by the presence of facultative anaerobes and the spores germinate.
• The cells multiply and produce 2 exotoxins:
  • Tetanolysin (a hemolysin), which is apparently insignificant.
  • Neurotoxic tetanospasmin, which travels along the peripheral nerves and binds to specific gangliosides of the motor nerve terminals and causes spastic paralysis and the characteristic spasms.
• Toxin may enter bloodstream and affect most susceptible motor nerve centers, which are those that serve the head and neck - first sign in this case is protruding third eyelid, tetanic spasm of facial and jaw muscle ('lock jaw').
• Wounds near head → more rapid onset of generalized signs.
• Localized tetanus can occur - stiffness of muscle or entire limb near wound site.

Other Host Effects

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

Control

Control via animal

• Clean and debride wounds.

Control via chemotherapies

• Sedatives.
• Supportive care.
• Penicillin G Benzylpenicillin.
• Antitoxin:
  • Does not hasten recovery, as bound toxin is cleared slowly.
  • Binds unbound toxin.

Vaccination

• Tetanus toxoid vaccines available.

Other countermeasures

• Prompt administration of anti-toxin.
• Supportive treatment: sedatives and muscle relaxants.
• Nursing care.
• Some have suggested intra-thecal administration of anti-toxin to horses, but this is not currently recommended.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Dieringer T M & Wolf A M (1991) Esophageal hiatal hernia and megaesophagus complicating tetanus in two dogs. JAVMA 199 (1), 87-89 PubMed.