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==Description==
==Description==
Tetanus is a rare disease in dogs. The disease pathophysiology is similar to that seen in the horse. The causal agent of tetanus in the dog is the neurotoxin of the gram-positive bacterium ''[[Clostridium tetani]]''. Infection occurs due to contamination of a wound by ''C. tetani'' and replication of the bacteria in the anerobic conditions provided by damamged and necrotic tissues. Tetanospasmin (neurotoxin) produced by the bacteria is transported to distant sites via the circulation and intraaxonally along peripheral nerves. This causes inhibition of the release of GABA and glycine from interneurons in the spinal cord and brain, resulting in persistent rigidity of striated muscle.
Tetanus is a rare disease in dogs, and the disease pathophysiology is similar to that described in other mammalian species. The causal agent of tetanus in the dog is the neurotoxin of the gram-positive bacterium ''[[Clostridium tetani]]''. Infection occurs due to initial contamination of a wound by ''C. tetani''. Replication of the bacteria occurs due to the anerobic conditions provided by the damamged wound tissues. Tetanospasmin (neurotoxin) produced by the bacteria is transported to distant sites via the circulation and intraaxonally along peripheral nerves. This causes inhibition of the release of GABA and glycine from interneurons in the spinal cord and brain, resulting in persistent rigidity of striated muscle and the typical clinical signs of tetanus.
==Diagnosis==
===Clinical Signs===
Because of their high natural resistance to tetanospasmin (compared to the horse and man), affected dogs may have a longer incubation period and clinical signs may be mild; a change in gait may be the only reported historical abnormality. The localised form of tetanus that develops in the dog may be difficult to diagnose, particularly if no wound is apparent. Unlike the generalised spastic paralysis described in horses, dogs may present with a wound to a single limb (often a thoracic limb) and unyielding stiffness or rigidity in the surrounding area. The rigidity may spread to the contralateral limb and then begin to advance cranially, becoming generalised as the disease progresses. As reported in horses, dogs may display hypersensitivity to even minimal amounts of stimulation. Affected animals have also been reported to display caudal displacement of the ears, lateral canthi and commissures of the eyes. Prolapse of the nictating membranes, trismus (excess jaw tone) and retracted lips (risus sardonicus) are other noted clinical features.
==Diagnosis==
As described above, a history of trauma and unrelenting muscular spasm in a localised area is often described in cases of tetanus in dogs. An obvious wound may help to increase suspicion of tetanus, particularly if the wound is necrotic or infected. In this species, diagnosis is often based on clinical judgement rather than laboratory tests, as these may add little helpful diagnostic information. In occasional cases, ''C. tetani'' may be cultured from a wound, but this may be impossible if healing has occurred or a wound is not apparent. An important clinical feature of tetanus in dogs that may aid diagnosis in hindsight is that of resolution of muscular spasm over a long period of time (weeks or months).
Other neurological diseases causing limb spasticity may need to investigated; myelography for example will assist in ruling out an extramedullary lesion. A complete blood cell count, serum biochemistry, survey radiographs of the thoracic spine and serology for protozoal diseases should also be performed in order to exclude other neurological differential diagnoses.
==Treatment==
==Treatment==