Botulism in Dogs

By Krista Williams, BSc, DVM, CCRP; Catherine Barnette, DVM

What is botulism?

Botulism is a rare condition that causes paralysis in dogs. Botulism is caused by ingesting the botulinum toxin, a substance produced by the bacteria Clostridium botulinum.

Most cases of botulism in dogs are caused by eating dead animals or contaminated raw meat. Clostridium botulinum that grows in/on meat can release the botulinum toxin into its surroundings, allowing the toxin to be ingested by dogs who eat the contaminated meat. When dogs eat contaminated meat, the toxin is absorbed by the intestines and enters the bloodstream. The botulinum toxin is then carried throughout the body, where it binds to nerve cells, resulting in paralysis.

What are the clinical signs of botulism?

Clinical signs of botulism typically develop hours to days after ingesting contaminated meat, though the onset can be delayed up to six days. Signs vary depending upon the amount of toxin ingested, although an earlier onset of clinical signs is typically associated with more severe disease.

Botulism often affects the body in a characteristic way. It often starts with weakness in the rear legs and, within 24 hours, this weakness progresses to include the front legs and muscles of the head and face.

"It often starts with weakness in the rear legs and, within 24 hours, this weakness progresses to include the front legs and muscles of the head and face."

Affected dogs are mentally normal. They can sense pain and are aware of their environment.

Botulism's effects on muscle movement may lead to an inability to swallow, increased salivation, constipation, and eye inflammation (due to decreased tear production and an inability to blink). In some cases, death may occur due to paralysis of the diaphragm. The diaphragm is the muscle that moves to inflate the lungs; when the diaphragm is paralyzed, a dog cannot breathe without the assistance of a mechanical ventilator. Fortunately, the diaphragm is better able to resist botulism paralysis than other muscles within the body; therefore, not all dogs require a ventilator.

How is botulism diagnosed?

Diagnosing botulism can be difficult. Your veterinarian will start by doing a full examination of your dog and taking a thorough history to determine possible opportunities your dog may have had to ingest the botulinum toxin, along with the signs your dog has been showing and their duration.

Routine laboratory tests, such as blood work and urinalysis, are typically normal in affected dogs, so diagnosis is usually based on a history of exposure and observation of the dog. Blood, stool, and/or vomit samples may be tested for the botulinum toxin. Radiographs (X-rays) may show evidence of pneumonia or esophageal motility problems, both of which can occur with this condition.

How is botulism treated?

If botulism exposure is known or suspected before the onset of clinical signs, the botulinum antitoxin can be administered. The antitoxin prevents the botulinum toxin from binding to nerve endings and causing clinical signs. Once signs of paralysis develop, the antitoxin is not effective.

Once signs have developed, treatment of botulism is focused on supportive care. This supportive care will require hospitalization; depending on the severity of your dog’s signs, he may require hospitalization at a facility with an intensive care unit.

"Once signs have developed, treatment of botulism is focused on supportive care."

The signs of botulism will typically resolve with time, and supportive care decreases the likelihood of complications. Affected dogs should be kept hospitalized on soft bedding, to prevent pressure sores. Mildly affected dogs may need assistance with eating or drinking, while more severely affected dogs may require intravenous fluids to prevent dehydration and a stomach tube for feeding.

Many affected dogs lose the ability to empty their bladder, so the veterinary staff may need to manually express your dog’s bladder or place a urinary catheter to keep the bladder empty. Your dog may require ointment to keep his eyes moist (if he is unable to blink). Antibiotics may be given to treat secondary infections that may occur. If your dog’s diaphragm becomes paralyzed, a mechanical ventilator may be used to allow him to breathe.

What is the prognosis for botulism?

Most affected animals recover within 14-24 days if they receive appropriate supportive care. Without treatment, death due to paralysis of the diaphragm or secondary infection may occur.

How can botulism be prevented?

To prevent botulism, ensure your dog does not consume raw meat or dead animals. There is no vaccine against botulism.

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