Tetanus and Animals
I saw a case of suspected tetanus this week in a cat so I thought we could take this opportunity to review this rare, but important, neurologic disease.
Tetanus is cased by the release of tetanus toxin by the Clostridium tetani bacterium. Once the toxin is produced in the wound, it travels via retrograde transportation from the peripheral nerve to the central nervous system where it attacks the real target: the inhibitory interneurons that regulate motor activity. So (you might ask), what is the lesion localization for tetanus? It is a CNS disease at the level of the spinal cord and brain NOT (as one might assume) a peripheral neuromuscular lesion localization!
Signs
The interneurons are focused on regulating muscle tone therefore a disruption of their function results spasticity. Remember, spasticity can occur in all skeletal muscles therefore diaphragm and intercostal muscles can be affected, resulting in respiratory paralysis. The spasticity can be stimulated by noise, touch and light. The incubation period for cats is 5-10 days with a longer suspected incubation period in dogs. According to a recent report about tetanus toxin, strychine intoxication is the only condition that exactly mimics the disease, however other myopathic diseases such as hypocalcemia can be included in the differential diagnoses in the early stages.
Treatment
Debridement of the wound(s) and antibiotics such as penicillin G and metronidazole are recommended to treat the infection but have no effect on the already-formed toxin circulating the body. Therefore, supportive nursing care is critical until a plateau in signs becomes evident. After this point, if the dog or cat can eat, drink, and void voluntarily, supportive care can be continued at home. Tetanus antitoxin is available for cases in which an early diagnosis is obtained however this has limited use in dogs and cats.
Prognosis
Recovery is expected for animals with appropriate supportive care. If respiratory paralysis occurs, ventilatory support may be needed, resulting in added expense and risk of secondary infections. However, a full recovery can be expected for dogs and cats affected by tetanus toxin with appropriate treatment and time.
A special shout out to the vets successfully managing this recent case. Keep it up and way to go!
Happy Thanksgiving! Stay safe, and keep those consults rolling.
Recent open access reference if you are interested: Popoff MR. Tetanus in animals. J Vet Diagn Invest. 2020 Mar;32(2):184-191. doi: 10.1177/1040638720906814. Epub 2020 Feb 18.