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BOTULISM. Botulism is a paralytic illness caused by a nerve toxin produced by the soil bacterium Clostridium botulinum and spread by contaminated food or by infection of a wound. The term comes from the Latin botulus (sausage), but the vehicle in food-borne cases today is usually vegetables or other food improperly canned at home. Commercial canning is almost never implicated, although a notable case in 1971 left one person dead and several others seriously injured. The illness is rare, with only twenty-five to thirty food-borne cases reported annually in the United States.

C. botulinum is a spore-forming bacteria that can lie dormant in the soil for months or years. In a warm, moist, low-oxygen environment, however, the spores can produce vegetative cells that multiply rapidly and secrete a deadly toxin, which attacks the nervous system of the person ingesting contaminated food.

Symptoms of botulism include double vision, blurred vision, drooping eyelids, slurred speech, difficulty in swallowing, dry mouth, and muscle weakness. An antitoxin can be used with early diagnosis, but otherwise treatment involves supportive care, sometimes including a ventilator. A severe case can require months of medical and nursing care and may leave the patient with permanent impairments. Botulism is fatal in about 8 percent of cases, usually from respiratory failure.

Thorough washing can remove the spores and proper heating will destroy them. If, however, the food being canned is not washed properly and fails to reach the necessary temperature for the required time, the spores can germinate and produce toxin in the canned goods.

A pH in the acid range will also kill the spores, so acidic foods such as fruit and tomatoes are less likely to be vehicles than low-acid food such as corn, green beans, or asparagus. Canners are often advised to raise the acidity of food by adding an acid source such as lemon juice or citric acid.

To avoid the danger of botulism, home canners of low-acid foods are advised to use a pressure canner instead of the unpressurized, boiling-water-bath systems used previously. A temperature of up to 250°F is needed, which can be reached with pressure canners operated at ten to fifteen pounds per square inch. The time required ranges from twenty to one hundred minutes, depending on the food and the size of the jars. Detailed instructions are available with home canning systems, either from the U.S. Department of Agriculture or from an extension agent.

Industrial quality control makes it highly unlikely that commercially canned food will be contaminated with botulinum toxin. However, consumers should reject any commercial canned goods that appear swollen or bulging and any canned food with a bad smell or flavor.

In recent years, scientists have recognized an infant form of botulism in which infants ingest spores that germinate and produce toxins in the intestines. This appears to be linked mainly to the ingestion of raw honey, so authorities urge parents never to feed raw honey to babies. There is little danger of this variant of the disease after the age of one year.

See also Packaging and Canning, History of; Packaging and Canning, Modern; Safety, Food.

Richard L. Lobb