The Tetanus Grin
Annelise Enslin (BVSc. BSc)
Tetanus is a condition that is caused by bacteria called, Clostridium tetani. The bacteria infects wounds where there is little to no oxygen and produces a toxin that affects nerves (neurotoxin) in a way that prevents muscles from relaxing, thus causing stiffness. This is different from some other neurotoxins that cause a “floppy” paralysis. Different species of animals have different degrees of resistance to the bacteria. Horses are relatively susceptible whereas dogs and cats seem to be more resistant. This however does not mean that they are never affected. With dogs in clinic we have seen it in association with toe nail injuries, tail docking (ringing), puppies losing their milk teeth. With horses being more susceptible it can occur with any form of wound. Therefore vaccines and anti-toxin are routinely used in this species.
Clinical signs usually consist of the following:
• Stiffness of a single limb that progress to affect all limbs
• Pricked up ears, lips pulled back at the corners, facial skin drawn back with wrinkles on the forehead and third eyelids coming up on both sides. This is classically referred to as the “sardonic grin.“
• Jaw becomes locked
• Sensitive to light and other stimuli like loud sounds or sudden movements Treatment in dogs:
• Large doses of horse anti-toxin
• Wound clean up
• In some cases, certain sedatives may help with muscle stiffness
• Intensive care involving syringe feeding, fluid administration by way of intravenous catheter if needed, if unable to stand frequent turning over
The anti-toxin will not do anything about the toxin that has already attached to and caused an effect in muscles. It will only neutralise the toxin that is still free-floating in blood and is still produced in the wound.
Care will continue until such a stage where the body has produced new, unaffected muscle receptors that allow normal contraction and relaxation. This may take several weeks.
Prognosis: If intervention occurs early in the disease process, the prognosis is good for recovery. However if left untreated for too long, the prognosis is poor as these dogs can suffer from fatal paralysis of the respiratory muscles and the inability to swallow resulting in choke or aspiration pneumonia.