Botulism and Dogs – A Rare but Very Serious Disease

In 2007, a food distributor primarily selling human-consumed products issued a recall for their canned meat products. The recall of Castleberry’s food products contained a shocking revelation for pet owners: several varieties of Natural Balance Pet Food were included in the recall. Based on the Food and Drug Administration’s testing and inspection of the facility that produced the food, a threat of botulinum toxin was found.

Botulism is a rare but very serious disease caused by a toxin released by the bacteria Clostridium botulinum. This group of bacteria is most commonly found in soil and thrives in low-oxygen conditions. Bacteria spores can remain dormant for long periods of time until environmental conditions change, supporting their growth.

There are seven main types of Clostridium botulinum: A, B, C1, D, E, F, and G. Types A, B, and E are the most commonly seen in humans. Type C1 is most commonly seen in animals, including dogs, ducks, chickens, and horses, while type D occurs in cattle.

The botulism toxin is prevalent in decomposing carcasses, spoiled vegetable materials, and decaying grass, hay, and grain.

Botulism is a relatively rare disease in the United States, with fewer than 150 human cases reported each year. Botulism in dogs is also rare, but because some dogs have a tendency to hunt and eat small animals such as foxes, chickens, opossums, and rabbits, the toxin is a concern for pet owners.

In contrast, there are three major types of botulism that can affect humans. Foodborne botulism occurs when people consume foods contaminated with botulism toxin. Like other foodborne illnesses, this can happen when food is not cooked properly or is handled incorrectly during processing. The Castleberry’s recall of human foods affected several lines of canned chili and hot dog sauces. More commonly, botulism may occur in homes that can their own food without heating it to temperatures high enough to kill off the spores.

Infant botulism is the most common form of botulism seen in the United States. It occurs in children under 12 months of age when germinating spores of the toxin colonize the intestinal tract, leading to serious and life-threatening illness.

Honey and other sweeteners have been linked to botulism in infants. The less acidic digestive juices in the stomach of young children make them less able to destroy spores that may be ingested in honey. Once ingested, body temperature and an oxygen-free environment create the optimal setting for the botulism spores to germinate, replicate, and release their toxin in the body.

Wound botulism can occur when a wound is contaminated with the Clostridium spore, usually from contact with soil. Rapidly closing wounds, such as punctures, are at an increased risk for developing botulism, as removing oxygen and the body’s temperature creates a perfect environment for the spore to grow and release toxins.

Humans and dogs differ greatly in their bodies’ reactions to the botulism toxin. In humans, signs of botulism can appear up to 14 days after exposure, making diagnosing the cause of illness difficult.

In humans, symptoms of botulism include double vision, drooping eyelids, difficulty swallowing, and progressive muscle weakness. Infants with botulism may appear lethargic, become constipated, and experience weakness. In both cases, the toxin released by Clostridium causes nerve and muscle paralysis. If left untreated, muscle weakness progresses first to the peripherals of the arms and legs, then to the vital organs and respiratory system, eventually leading to death by respiratory failure.

Symptoms of Botulism in Dogs

In dogs, symptoms typically occur more quickly, usually within 12-36 hours after exposure to the toxin. Symptoms of botulism in dogs may include generalized weakness, paralysis that spreads from the hind limbs to the forelimbs, increased respiratory effort, facial nerve paralysis, and difficulty swallowing. As in humans, if left unchecked, the disease progresses to fatal respiratory failure.

Compared to many other species, dogs are relatively resistant to the toxin, which is why botulism in dogs is quite rare. Almost all cases of botulism in dogs are precipitated by the consumption of a dead animal carcass. Due to its rarity, it can be difficult to differentiate botulism toxicity from other diseases and disorders. Ingestion of some poisons, nervous system infections or injuries, Myasthenia gravis, drug reactions, and strokes can mimic the symptoms of botulism in dogs. Diagnosis often relies on owner observation of the dog’s exposure to animal carcasses, and sometimes detection of spores in fecal samples. Laboratory tests can also detect botulism in the blood of affected animals, but delays in test results make testing more of a means of satisfying curiosity rather than a tool for timely treatment.

In both dogs and humans, treatment is mostly limited to supportive care, such as respiratory therapy and nursing care. It can take several weeks to see improvement in paralysis, and even longer for the body to return to normal functioning. For this reason, botulism in dogs is often fatal, as the resources required to maintain a dog in an animal hospital at the level of care required are often too great.

An equine-derived antitoxin has been used with some success in both human and canine cases of botulism. However, for it to be effective, the antitoxin must be administered in the early stages of infection, rendering it almost ineffective once clinical signs of botulism are present.

In humans, botulism can often be prevented by ensuring proper methods for canning foods at home are followed. Foodborne botulism has most frequently been seen in asparagus, green beans, beets, corn, chile peppers, tomatoes, baked potatoes, and home-canned fish. High temperatures destroy botulism spores, and boiling home-canned foods for 10 minutes prior to consumption can help ensure safety. Because honey can contain spores of Clostridium botulinum, it should not be fed to children under 12 months but poses no health risk to those over the age of 1. Prompt medical attention and wound care can help prevent wound-based botulism.

In dogs, the best prevention is to prevent access to dead animals and carcasses. Monitoring your dog’s activities while outdoors and regularly surveying large yards and outdoor areas can help identify and remove potential threats to your dog’s health before they find them.