Tetanus

Tetanus in Horses

Tetanus in Dogs

Also known as:

Lockjaw

Description

Tetanus is a rare disease in dogs. The disease pathophysiology is similar to that seen in the horse; the causal agent the neurotoxin of the gram-positive bacterium Clostridiu tetani. Infection occurs due to contamination of a wound by C. tetani and replication of the bacteria in the wound's anerobic environment. 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 tetanic spasm of striated muscle. Because of their high natural resistance to tetanospasmin, affected dogs may have a longer incubation period than that described in the horse. Dogs may often develop a localised tetanus rather than the generalised tetanus seen in other species.

Diagnosis

Clinical Signs

The localised form of tetanus seen in dogs may cause differing clinical signs to those seen in other species. Unlike the generalised spastic paralysis seen in horses, dogs may present with an obvious wound and stiffness or rigidity in a single limb. The rigidity may spread to the contralateral limb and then begin to advance cranially. Dogs may often display hypersensitivity to even minimal amounts of stimulation. Affected cases have been reported to display caudal displacement of the ears, lateral canthi and commissures of the eyes. Dogs may also display prolapse of the nictating membranes.

Treatment

The approach to treatment in the dog is the same as that described for the horse. it is important however to exercise caution in the intravenous administration of equine tetanus antitoxin as this may cause anaphylaxis if used in dogs.

Noise and external stimuli should be kept to a minimum. The dog should be kept in a quiet, darkened kennel positioned away from other dogs.

In the recovery stage, physiotherapy may be of some benefit.

Supportive nursing care such as catheterisation and/or enemas may be required. Bedding should be thick and changed regularly in order to prevent decubital ulcer formation.

References

• Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial