You’ve probably heard of a tetanus shot and vaguely know that you’re supposed to get one from time to time but especially after a dirty cut, scratch from a piece of metal, or some sort of bite wound. You may even know that tetanus is often referred to as “lockjaw.” But beyond that, you may not have much knowledge about tetanus—including the fact that it can be dangerous for your dog, too.
Different animal species have varying sensitivities to the tetanus neurotoxin. Horses, humans and livestock are most sensitive and dogs are less sensitive (cats are very resistant and almost never get infected). Below, everything you need to know about tetanus in dogs, including symptoms to lookout for and exactly how to treat it.
What Is Tetanus?
Tetanus is a very serious disease caused by a neurotoxin called tetanospasmin that is secreted by a bacterium known as Clostridium tetani. The neurotoxin affects the nervous system of dogs, which can lead to painful stiffening and paralysis of the dog’s jaw, neck, and other muscles. The toxin binds to local nerves and moves up into the central nervous system where it interferes with the release of glycine, an amino acid that also acts as an inhibitory neurotransmitter. The result: painful muscle over-activity, spasms, and rigidity in the dog’s muscles. In severe cases of tetanus, a dog cannot breathe because the respiratory muscles become paralyzed. In these cases, a mechanical ventilator is needed.
Tetanus bacteria are anaerobic, meaning they grow in conditions where there is no oxygen, such as a deep bite wound or puncture. Clostridia are soil bacteria and they live in dirt, so it is easy to see how a puncture on a dog contaminated with dirt would be a classic tetanus-yielding wound. Such wounds are particularly common on farms where there might be nails on the ground, ready to pierce a dog in the foot. A fight involving a bite wound and rolling around in dirt might also lead to tetanus in dogs.
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Another interesting source of exposure to tetanus for dogs are foxtails, a grass-like weed found in the western U.S. A study performed at UC Davis School of Veterinary Medicine looked at 35 cases of canine tetanus and found the initial wound for 27% of the dogs treated was a foxtail tract, and an additional 50% of wounds were suspicious of foxtail tract!
Symptoms Of Tetanus In Dogs
- Inability to blink
- Constricted pupils
- Sunken eyes
- Sensitivity to light
- Risus sardonicus (a sardonic grinning)
- Erect ears
- Inability to open jaw
- Rigid tail
- Sawhorse stance
- Difficulty swallowing
- Muscle spasms
- Walking rigidly or inability to walk
Initial signs of tetanus in dogs are usually issues with their eyes and can easily be mistaken for eye disease in the early stages. Classically, a dog loses the ability to blink and must flash their third eyelid to moisten their eye. A dog may become so sensitive to light and sound that clapping your hands can create spasms or seizures. In this phase of disease, these signs may be attributed to other toxins, such as snail bait or moldy toxins, resulting in a misdiagnosis.
Dogs with ears that hang down may develop ears that stand up straight, and the facial muscles may pull back creating risus sardonicus (aka, a sardonic grin). In more advanced stages, a dog can no longer walk and will stand stiffly in what is called a sawhorse stance.
Diagnosis of Tetanus in Dogs
Unfortunately, there is no easy diagnostic test that can confirm tetanus in dogs. The diagnosis is generally made based on the visual appearance of the dog and history of the wound. Typically, there is a history of a wound in a tetanus case (usually in the preceding 1 to 2 weeks) but sometimes the wound may have gone unnoticed by the human and this important clue is not available.
It’s possible to measure antibody levels against the tetanus toxin, but this has not been widely used in clinical settings. Attempting to culture Clostridium tetani from the wound, as a way to support a diagnosis, usually doesn’t work.
Treatment of Tetanus in Dogs
The first step in treatment is antibiotics to kill the Clostridia toxin. The good news is, exotic antibiotics are not needed—good ol’ fashioned penicillin does the trick. In addition to the antibiotics, sedation and anti-seizure medications may be necessary to control the muscle spasms and/or seizures.
Nursing care may also be needed and requires a darkened room with minimal stimulation and soft bedding to prevent bedsores. The clenched jaws caused by tetanus can be problematic for feeding so a liquid diet or slurry is often necessary. Improvement is generally noted within the first week of therapy but complete recovery can take a month.
A controversial treatment called Tetanus Antitoxin may be an option, if the tetanus is diagnosed early. Antitoxin is an antibody solution (a blood product) generated by either a horse or human blood which works by binding and destroying the tetanus toxin, preventing it from attaching to the dog’s cells. Unfortunately, if the toxin has already attached to the cells, the antitoxin will not work; in fact, the tetanus antitoxin can actually cause significant side effects in dogs, so your veterinarian will weigh the risks versus the benefits.
What About A Tetanus Shot?
Tetanus toxoid is the tetanus shot most of us (humans) have had at one time or another. It is a vaccine against the tetanus toxin and it is part of our own human vaccination set. Because dogs are much more resistant to tetanus than humans, regular vaccination against tetanus is not recommended for them.
Luckily, tetanus is not common in dogs. But the potential does exist, so it’s always good to have this knowledge…you never know what kind of mischief your dog will get into!