How Much Do You Know About Botulism?

You can get botulism in three ways: by eating foods that contain the botulism toxin, by eating foods that contain spores of the bacteria, or through a wound infected with the bacteria. C. botulinum is an anaerobic bacterium, meaning it grows in places where little oxygen is present. Like many bacteria, C. botulinum reproduces by forming spores, which can lie in a dormant state until conditions are right for growth. Infant botulism occurs when an infant consumes spores of the bacteria, which then grow in the intestines and release toxin. In the United States, about 110 cases of botulism are reported each year. Of these, about 25 percent are foodborne, 72 percent are infant botulism, and the rest are wound botulism.

Foods with a low acid content such as asparagus, green beans, beets, and corn seem especially vulnerable to contamination by the botulinum bacteria. Other sources have been chopped garlic in oil; chile peppers; tomatoes; potatoes baked in foil; frozen, fully cooked foods; and home-canned or fermented fish. Spores are often found on the skin or rind of fruits and vegetables and in seafood. The bacteria and spores themselves are harmless; the dangerous substance is the toxin produced by the bacteria when they grow. The other foods listed as answers (raw tuna, raw eggs, and mayonnaise on a hot day) may also cause foodborne illness, but the culprits are not the botulinum bacteria toxin.

An infant's intestinal tract presents an inviting environment for C. botulinum toxin production because the tract has not yet developed the full range of beneficial bacteria present in the intestines of older children and adults. Bees can pick up spores of C. botulinum when they gather pollen; the spores then become part of the honey produced by those bees. Although honey is considered safe for adults and children older than a year, it should not be given to infants. Because the spores are nearly everywhere in the environment, children and adults regularly ingest them, yet very rarely suffer ill effects. Infants with botulism appear lethargic, feed poorly, are constipated and have a weak cry, and poor muscle tone.

Once in the body, the botulism toxin binds to nerve endings at the point where the nerves join muscles. This prevents the nerves from signaling the muscles to contract. The result is weakness and paralysis that starts at the head and works downward through the body, eventually affecting the muscles that regulate breathing. Other symptoms include blurred vision, difficulty swallowing, and dry mouth. The first symptoms usually are double vision and blurred vision. Symptoms usually appear 18 to 36 hours after eating a contaminated food, but they can show up as early as 6 hours or as late as 10 days.

C. botulinum is a common bacterium, but to get botulism a person must eat food containing the toxin the bacterium produces. This is food that has not been properly cooked or has been reheated after the toxin is present. For infant botulism, the infant must ingest the spores, which then produce the toxin in the infant's intestinal tract. (Wound botulism is another way to contract botulism, when the bacteria enter a wound and produce toxin.)

To rule out these other diseases, a doctor will use tests, including a brain scan, spinal fluid check, electromyography, and a tensilon test. Botulism is confirmed by finding the botulinum toxin in the food a person ate, in the person's blood or feces, or cultured from a wound. It's important to make the diagnosis, particularly for foodborne botulism, to help others avoid the contaminated food.

A person with severe botulism may need to be connected to a respirator for weeks during recovery and remain in intensive care. The paralysis caused by the botulism toxin gradually eases. An antitoxin can be given to adults if the diagnosis is made early enough; it stops the person's condition from getting worse. The doctor may induce vomiting or give an enema early on to remove any contaminated food still in the digestive tract.

You can obtain a copy of home-canning guidelines from your county agricultural extension office. The botulism spores in home-canned foods can only be killed by the high heat (above 212 degrees F for 10 minutes) of a pressure canner. The botulism toxin can only be destroyed by boiling foods for 10 minutes. Commercially prepared foods also have been involved in botulism outbreaks. Some outbreaks have been caused by improperly handled restaurant foods such as potato salad. Many outbreaks involving commercially prepared foods have been caused by consumers' mishandling of foods; for instance, by not refrigerating foods clearly labeled as needing refrigeration. Protect yourself against botulism by reading food labels and following storage instructions. Bulging home-canned containers should not be opened. Discard packages that appear damaged and commercially canned products with bulging or rusty lids.

In treating facial wrinkles, dermatologists inject very low doses of the toxin into the skin. The toxin paralyzes the facial muscles, smoothing out wrinkles. Ophthalmologists use the toxin to treat the blurred vision caused by some eye diseases. The injected toxin also appears to help ease the pain of migraine headaches. Injections usually have to be repeated, because the effects usually last only three to four months, although sometimes they can last for more than a year. Because of this, up to 10 percent of patients eventually develop antibodies to the toxin. This is more likely in patients who receive higher doses at more frequent intervals. Therefore, the manufacturers recommend that its dosage be kept as low as possible.