Warmer weather always makes me want to throw off my shoes and run barefoot through the grass. But then I come to my senses when I realize how many potential dangers are lurking out there just waiting to infect me! As if being an adult isn’t bad enough, being a veterinarian just makes it worse; we know about all of the creepy crawlies hiding in the dirt – as well as all of the springtime health hazards that can affect our pets!
One potential danger that I’m sure you know about is tetanus, though you may know it better as lock jaw. The notorious rusty nail seems to get all the blame in human medicine, but did you know that animals are susceptible to tetanus as well? While cats and dogs are more resistant to tetanus than humans and horses, they are susceptible to the disease, so I thought I’d take today’s blog to tell you more about it.
Tetanus is caused by a neurotoxin produced by the bacteria Clostridium tetani. This bacterium is found worldwide, and its spores are resistant to degradation. It can persist in the environment for months to years. Bacterial spores are introduced into wounds, especially through penetrating injuries (like those caused by stepping on a rusty nail).
Once in the wound, the spores vegetate and produce toxin. The toxin enters local nerves and ascends up the spinal cord to the brain. The toxins work to block neurotransmitters that inhibit muscle activation, so the end result is generalized overactivity of muscles. Muscles can’t relax. (The opposite reaction – flaccid paralysis – is seen in tetanus’s sister bacteria, botulism.)
Clinical signs typically occur within five to ten days of infection, although they can occur sooner if the wound is particularly close to the central nervous system. There is no test for tetanus. Your veterinarian will likely go on clinical signs and a history of a recent trauma or wound.
Because dogs and cats are more resistant to tetanus, localized tetanus is more common than generalized tetanus. In localized tetanus, muscle stiffness would be localized to the limb closest to the wound. Over time, stiffness can spread to the opposite limb and then to the whole nervous system.
Generalized tetanus involves multiples sites; a generalized stiff gait is observed along with an outstretched tail. Dogs with droopy ears may hold their ears up, and you may notice that dogs and cats with generalized tetanus may have a wrinkled forehead and hold their lips drawn back. This is due to contracted muscles that can’t relax. And all of these are signs of a veterinary emergency.
In severe cases, animals are so stiff that they cannot walk and can only lie on their sides. Aspiration pneumonia causes coughing and respiratory distress, while urine and feces retention can cause discomfort as well. In worst case scenarios, death from respiratory paralysis can occur.
Treatment of tetanus will require a hospital stay. The prognosis is usually good, especially if the tetanus is localized rather than generalized. In generalized tetanus, a tetanus antitoxin will be given to bind remaining circulating toxin. Antibiotics and other supportive treatments, such as IV fluids and sedatives to control muscle spasms will be administered as needed. Wound management to address the initial infected wound will also be performed.
Unlike in humans, the use of tetanus toxoid (or the tetanus shot) is not routine in dogs and cats because their susceptibility is lower than ours, so avoiding tetanus is a matter of vigilance when pets are parading through the spring grass!