Mechanism of toxicity
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- Three exotoxins are produced by the vegetative form of C. tetani.
- Transport to the CNS occurs retrograde within nerves and via the bloodstream .
- The toxin binds to gangliosides in the brain stem or spinal cord.
- It blocks inhibitory synaptic input, especially at glycine mediated sites, by binding to the presynaptic membrane and blocking the release of glycine , resulting in spastic paralysis.
- It may also inhibit release of GABA and other amino acid neurotransmitters.
- Tetanus toxin may also cause paralysis by inhibiting the release of acetylcholine at neuromuscular junctions.
- Constant muscular spasticity may be produced and normally innocuous stimuli cause exaggerated responses.
- Death occurs as a result of rigidity of the muscles of respiration and associated asphyxia.
Susceptible species
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Although all species of domestic animals are susceptible to tetanus, most cases appear to occur in the horse.
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Horses are the domestic species most sensitive to tetanus toxin.
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Pigs, cattle and sheep are less sensitive and dogs and cats are fairly resistant but are sometimes affected.
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Poultry are more resistant.
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Generally, tetanus occurs in individual animals although outbreaks have been described in cattle, young pigs and lambs.
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Last modified: Saturday, 20 August 2011, 11:40 AM