Tetanus and Dogs

What is tetanus?

Tetanus is caused by the Clostridium tetani bacteria which produces a neurotoxin that causes muscle contractions. This bacterium is found commonly in soil and is ubiquitous throughout the world. After the bacterium is injected into an anaerobic environment it produces the toxin. The toxin targets inter neurons in the spinal cord, inhibiting their function.

Diagnosis?

A diagnosis is made by observation of classic clinical signs such as limb rigidity, muscle retraction on the face or periocular. Detection of the C. tetani bacterium in the wounds through culture can provide a definitive diagnosis, if obtained.

Treatment?

Wound debridement followed by appropriate antibiotics (penicillin or metronidazole) will result in recovery for the majority of dogs and cats. For severe cases, respiratory assistance with a ventilator, sedation to avoid painful sustained muscle contractions and 24-hour nursing care may be needed.

Seasonality?

An interesting article came across my view recently that identified a spike in tetanus cases in the winter months (December-February) in England. This was surprising because more cases are reported in warm, humid climate than cold ones. The authors didn't provided substantial reasoning for the odd seasonality but suggested it may be related to the exposure by walking in wet muddy environments. Here is the link to the article if you'd like to read more: https://doi.org/10.1111/vec.13068

I hope you have a wonderful, productive, safe week and I look forward to working with you soon. Thanks for reading!

Tetanus and Animals

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.