- Causes tetanus (maily in horses)
- Acute, potentially fatal intoxication affecting many species
- Horses and man particularly susceptible; carnivores fairly resistant
- Found in horse faeces
- Characteristics:
- Terminal, spherical endospores give mother cells a drumstick appearance
- Endospores resistant to boiling and chemicals but susceptible to autoclaving
- Swarming growth and haemolytic on blood agar
- Many serotypes but all produce same neurotoxin, tetanospasmin, therefore antibodies neutralise all
- Pathogenesis:
- Endospores introduced via damaged tissues e.g. penetrating wounds
- Damaged tissue creates an anaerobic environment, allowing germination of spores
- Tetanospasmin made by bacteria replicating in damaged tissue
- Absorbed toxin affects neuromuscular junction distant from site of toxin production
- Neurotoxin binds irreversibly to ganglioside receptors on motor neurons and is transported to nerve cell body
- Toxins transported across synapse to terminals of inhibitory neurons where they block transmission of signals
- Spastic paralysis by constant tensing of muscles results
- Toxin can be blood-borne and bind to motor terminals throughout the body as well as in the CNS
- Clinical signs:
- Incubation period 5-10 days
- Stiffness, localised spasms, altered heart and respiratory rates, dysphagia, altered facial expression, lock-jaw from mastigatory muscle spasm
- Tonic muscle contraction easily stimulated
- Treatment:
- Antitoxin IV or into subarachnoid space on 3 consecutive days
- Toxoid subcutaneously to promote active immune response
- Penicillin to kill vegetative cells
- Debridement and flushing of wound with hydrogen peroxide
- Fluids, sedatives, muscle relaxants
- Control:
- Toxoid vaccine for farm animals
- Debridement of wounds in horses