Botulism in Dogs

What Is Botulism in Dogs?

Botulism is a rare but potentially fatal illness caused by a toxin produced by the bacteria Clostridium botulinum. Dogs become affected by eating decomposing animal carcasses or spoiled vegetation where the bacterium grows. Once eaten and absorbed from the stomach and intestines, the toxin attacks the body’s nerves, resulting in weakness (paresis), and eventually the inability to move (paralysis). This can progress quickly to breathing difficulties or even eventual death, if left untreated.  

Botulism is considered a medical emergency and can be deadly without prompt treatment. If you believe your pet is experiencing any of the signs of botulism, contact your local veterinarian immediately.

Symptoms of Botulism in Dogs

Clinical signs of botulism may develop within a few hours but can be delayed up to six days. Signs can vary based on the amount of toxin consumed, but the earlier the signs appear, the more serious the disease. Clinical signs of botulism include:

• Vomiting/diarrhea   

• Progressive, symmetrical, ascending weakness that begins in the rear limbs. This is a classic hallmark sign of botulism in dogs. It means weakness that began in the back legs has moved up the body to the front legs, and then to the head and neck. As this occurs, you may see these additional symptoms:

  • Inability to walk

  • Inability to hold up the neck and head

  • Facial paralysis including decreased jaw tone, decreased ability to chew or swallow, and drooling or hypersalivation

  • Urinary retention (unable to pee) and constipation (unable to poop)

  • Difficulty breathing

  • Paralysis of all four limbs (quadriplegia)

Despite being paralyzed, affected dogs are mentally normal, and can still sense their environment and feel pain.

If left untreated, most pets die of botulism due to respiratory distress as the muscles used for breathing, such as the diaphragm, becomes paralyzed and the dog is unable to breathe. However, the paralysis can affect other organs, such as the heart—which can also be fatal. If your pet is experiencing any of the above clinical signs of botulism, contact a veterinarian immediately.  

Causes of Botulism in Dogs

Botulism is caused by the botulinum toxin, which is produced by the bacteria C. botulinum. There are seven subtypes of C. botulinum (A, B, C, D, E, F, and G). All of them have the same effect on the nervous system. Subtypes A, B, E, and F are associated with botulism in humans while most cases in dogs are caused by subtype C.

Once a dog consumes the toxin, it is absorbed in the stomach and intestines and carried in the bloodstream to the nerves. Nerves in the body are used to signal muscles to contract. Botulinum toxin blocks this process so that the muscles are unable to contract, creating muscle weakness and paralysis.

The diaphragm muscle is the muscle separating the abdomen and thorax. Its contraction plays a major role in breathing. Luckily, it is more resistant than other muscles in the body to the botulinum toxin, but once affected, a dog cannot breathe and, without therapy, will die.

How Veterinarians Diagnose Botulism in Dogs

Botulism in dogs can be very hard to diagnose because it is very rare, and the paralysis can mimic other diseases such as tick paralysis, intervertebral disc disease, degenerative myelopathy, toxins, myasthenia gravis, nerve and muscle disease. It is very important to share any history of possible exposure to carcasses, dead animals, rotting vegetation, or raw meat with your veterinarian.

Your veterinarian will start with a thorough physical examination to assess weakness, spinal reflexes, pain, and fever. They will also perform a complete orthopedic and neurologic examination.

Current tests to diagnose botulism involve highly specialized laboratory testing to detect the botulinum toxin in blood, feces, vomit, or in the ingested material. However, these tests are neither timely nor accurate enough to typically establish a diagnosis in time to be useful. Therefore, the diagnosis is typically made based on the history, clinical signs, while ruling out other illnesses with similar signs.

A complete blood count, serum blood chemistry, and urinalysis will likely be recommended for a baseline evaluation, and to help rule out other causes of paralysis. An X-ray may be taken to assess for signs of pneumonia or changes in the esophagus (megaesophagus) commonly seen with botulism.

Treatment of Botulism in Dogs

While there is an antitoxin for botulism, it is not readily available in veterinary hospitals and must be given before the toxin reaches the nerve endings and causes clinical signs. Once a pet develops signs of paralysis, the antitoxin is not effective.

Treatment of botulism in dogs is mainly supportive care. This supportive care can be time-consuming and expensive as it will require hospitalization, likely in an intensive care unit (ICU). Mildly affected dogs may be able to continue to eat and drink on their own with assistance, while more severely affected dogs will likely need IV fluids (to keep them hydrated) and feeding tubes.

Care must be taken to provide sufficient bedding/padding and rotation of positioning to prevent an unmoving patient from developing bed sores. Urinary care must also be tended to either by keeping the patient clean and dry or, if the dog loses the ability to urinate, providing manual bladder expression or urinary catheter care. Antibiotics and supportive medications, including medications for eye lubrication, pain, nausea, or diarrhea may also be given.

If the paralysis continues to progress and affects the diaphragm, dogs may lose the ability to breathe on their own and require manual ventilation with a ventilator.

Recovery and Management of Botulism in Dogs

The botulinum toxin does not damage the nerves, but rather blocks the signals to the muscles to contract. Since there is no nerve damage, supportive care often results in complete recovery. However, clinical signs of botulism often last for two-to-three weeks, and pets may need intense supportive care the entire time.

Prevention of Botulism in Dogs

Prevention is key to protect dogs from botulism. Never let your dog ingest raw meat, dead animals, or spoiled vegetation. It is best to keep a close eye on them when outside or in wooded areas. Unfortunately, there is no vaccine against botulism for dogs.