Botulism in Dogs

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 meat can release the botulinum toxin into its surroundings, allowing the toxin to be ingested by dogs who eat the contaminated meat. The toxin is then 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 12–72 hours after ingesting contaminated meat, though the onset can be delayed up to six days. Signs vary depending on the amount of toxin ingested. An earlier onset of clinical signs is typically associated with more severe disease.

Botulism 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 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, so not all dogs require a ventilator.

How is botulism diagnosed?

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

Diagnosis is usually based on a history of exposure and observation of the dog, as routine laboratory tests (e.g., blood work and urinalysis) are typically normal in affected dogs. 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 are seen with this condition.

How is botulism treated?

If botulism exposure is known or suspected before clinical signs begin, 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 of botulism have developed, treatment is focused on supportive care. This supportive care will require hospitalization, and may require intensive care, depending on the severity of your dog’s signs.

Signs of botulism typically resolve with time, and supportive care decreases the likelihood of complications. Affected dogs should be kept on soft bedding while hospitalized 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. Dogs that are unable to blink may require ointment to keep the eyes moist. 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 it 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 may occur, due to paralysis of the diaphragm or secondary infection.

How can botulism be prevented?

You can prevent botulism by preventing your dog from eating raw meat or dead animals. There is no vaccine against botulism.