Botulism and Dogs

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In 2007, a food distributor of primarily human-consumed products issued a recall of their canned meat products. The recall of Castleberry's food products contained one shocking revelation to pet owners, when several varieties of Natural Balance Pet Food where included in the recall.  Based on the Food and Drug Administrations 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 that is 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 lay dormant for long periods of time until environmental conditions change that support 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 types most commonly seen in people. C1 is seen in most animal cases, including dogs, ducks, chickens and horses, and type D occurs in cattle.

The source of the botulism toxin is prevalent in decomposing carcasses, spoiled vegetable materials as well as decaying grass, hay and grain.

Botulism is a relatively rare disease in the United States, with fewer than 150 human cases a year. Botulism and dogs has proven to be a relatively rare occurrence, but because of some dogs’ penchant for hunting and eating small animals such as foxes, chickens, possums, rabbits, etc, the toxin is a concern to pet owners.

In contrast, there are three major types of botulism that can be acquired in humans. Eating foods infected with the botulism toxin causes food borne botulism. Like other food borne illnesses, this can occur when food is not cooked properly, or is handled incorrectly in processing. The Castleberry’s recall of human foods encompassed several lines of canned chili-and-hot-dog sauces. More commonly, botulism may occur in homes that can their own food, and are not heated to temperatures high enough to kill off the spores.

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

Honey and other sweeteners have been shown to be an adjunct 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 optimum setting for the botulism spores to germinate, replicate and release their toxin within 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 increased risk for developing botulism, as removal from oxygen and the bodies’ temperature create a perfect environment for the spore to grow and release toxin.

Humans and dogs differ greatly in their bodies’ reaction to the botulism toxin. In humans, signs of botulism can occur as long as 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 can appear lethargic, and become constipated and become weak. In both cases, it is the toxin given off by the clostridium that 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 causing death by respiratory failure.

Symptoms of Botulism in Dogs

In dogs, symptoms typically occur more quickly, usually only 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, the unchecked the disease progresses to fatal respiratory failure.

Compared to many other species, dogs are relatively resistant to the toxin, and as such botulism and dogs is quire rare.  Almost all incidence of botulism in dogs is precipitated by the consumption of the carcass of a dead animal. Due to its rare occurrence in dogs, it can be difficult to differentiate botulism toxicity from other diseases and disorders. Ingestion of some poisons, nervous system infection or injury, Myasthenia gravis, drug reactions and stroke can mimic the symptoms of a botulism infection in dogs. Diagnosis often is based on owner observation of the dog, exposure to animal carcasses, and sometimes detection of the spores in fecal samples. Laboratory tests can also be employed to detect botulism in the blood of affected animals, but the delay in test results make testing more of a means of satisfying curiosity than of use to treating an animal in a timely fashion.

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

An equine-derived antitoxin has been used with some success in human and canine cases of botulism.  However, in order 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 be prevented in many cases by ensuring the proper methods for canning foods at home have been used. Foodborne botulism has been seen most frequently in asparagus, green beans, beets and corn, as well as Chile peppers, tomatoes, baked potatoes and home-canned fish. High temperatures destroy botulism, and boiling home-canned foods for 10 minutes prior to eating can help to ensure safety.  Because honey can contain spores of Clostridium botulinum, it should not be fed to children under 12 months, but is not a health risk for persons over 1 year of age.  Prompt medical attention and wound care can help to prevent wound-based botulism.

In dogs, the best prevention of botulism is to prevent access to dead animals and carcasses. Monitoring your dogs’ activities while outdoors, and regular surveys of large yards and outside areas can help you identify and remove potential threats to your dogs health, before your dog can find it.

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