Dogs & Tetanus: Not Just from Rusty Nails

Surprisingly, foxtails are another source of the tetanus toxin.
By Shea Cox DVM, October 2011, Updated September 2020
Tetanus & Dogs

We have all heard of tetanus shots and have some sense that we are supposed to periodically get them, especially after a dirty cut, scratch with a piece of metal or some sort of bite wound. Some of us may even know that tetanus is often referred to as “lock jaw,” but the general knowledge of tetanus generally does not extend much beyond that, and many people are not aware that tetanus can be a problem for animals as well as people.

Can Dogs Get Tetanus?

Different animal species have different sensitivity to the tetanus neurotoxin. On the spectrum of tetanus sensitivity, horses, humans and livestock are most sensitive and dogs are less sensitive. And then there are cats: They are quite resistant and almost never get infected (as we all know, cats have a different rule book than the rest of us). We will, of course, focus on our best friend, the dog. So, while less likely than humans, yes, dogs can get tetanus too!

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.

Here comes the nerdy part: 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 of this loss of inhibition is painful muscle over-activity, spasms and rigidity in the dog’s muscles. In severe cases of tetanus, the dog cannot breathe because of the rigid paralysis of the respiratory muscles and a mechanical ventilator is required.

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Tetanus bacteria are anaerobic, meaning that 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 the classical 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 offer an opportunity for tetanus in dogs.

Another interesting source of exposure to tetanus for dogs are foxtails. 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! An important take away of this study: The wound does not need to be a bite or traumatic puncture. Yet one more reason to fear the foxtail!

Read more:  Protecting Your Dog Against Foxtails by Shea Cox, DVM

Symptoms of Tetanus in Dogs

  • Inability to blink
  • Constricted pupils
  • Sunken eyes
  • Sensitivity to light
  • Risus sardonicus
  • Erect ears
  • Inability to open jaw
  • Rigid tail
  • Sawhorse stance
  • Difficulty swallowing
  • Seizures
  • Muscle spasms
  • Walking rigidly or inability to walk

Initial signs of tetanus in dogs seem to pertain to the eyes and can easily be mistaken for eye disease in the early stages. Classically, the dog loses the ability to blink and must flash the third eyelid to moisten the eye. The patient becomes 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 pull back in such a way as to create what is called risus sardonicus, or the sardonic grin. In more advanced stages, the patient can no longer walk and will stand stiffly in what is called a sawhorse stance.

Diagnosis

Unfortunately, there is no easy diagnostic test that can be performed to give veterinarians the answer. The diagnosis of tetanus in dogs is generally made based on the visual appearance of the dog and history of a wound. Typically, there is a history of a wound in a tetanus case (generally in the preceding 1 to 2 weeks) but sometimes the wound may have gone unnoticed by the owner and this important clue is not available.

It is possible to measure antibody levels against the tetanus toxin, but this has not been widely used in the clinical setting. Attempting to culture Clostridium tetani from the wound, as a way to support a diagnosis, is generally not successful.

Treatment

The first step in treatment is antibiotics to kill the Clostridia toxin. Happily, 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 is a cornerstone of treatment for dogs 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 needed.

Improvement is generally noted within the first week of therapy but complete recovery can easily take a month.

A controversial treatment called Tetanus Antitoxin, may be an option if 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 on to the dog’s cells. Unfortunately, if the toxin has already attached to the cells the antitoxin will provide no benefits, in fact the tetanus antitoxin can actually cause significant side effects in dogs, so the veterinainan will examine the risks.

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 tatanus is not a common occurrence for dogs. However, the potential does exist and it is always good to have this knowledge… you never know what kind of medical mischief our dogs will get in to!

Photo by Alan Quirván

Shea Cox earned a veterinary medical degree from Michigan State University in 2001 and has been practicing emergency and critical care medicine since. In 2006, she joined PETS Referral Center. In her spare time, she loves to paint, wield her green thumb and cook up a storm. She shares her days with the three loves of her life: her husband Scott and their two Doberman.