Health A-Z

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What Is It?

Botulism is a form of poisoning caused by exposure to Clostridium botulinum bacteria. These bacteria manufacture a chemical poison known as botulinum toxin that interferes with muscle function in many areas of the body, causing paralysis of individual muscles or groups of muscles. Exposure to this toxin is life threatening, since one of the muscles it can paralyze is the diaphragm, the muscle that controls breathing.

You can be exposed to the bacteria causing botulism in several ways, the most familiar being by eating contaminated food. In most food-borne cases of botulism in adults, home-canned foods are responsible. The bacteria that cause botulism exist in dirt and dust as a spore, but this form is inactive and does not produce toxin. When a spore is moved into a low-oxygen environment, however, such as an enclosed jar or can, it can reproduce and make its dangerous toxin.

Home-canned vegetables that are not highly acidic (asparagus, green beans, peppers, beets and corn) are good incubators for botulism bacteria unless they are heat-treated appropriately to kill the spores during the canning process and eaten quickly after opening. The bacteria can release large quantities of toxin into the canned food jar, causing botulism symptoms in people who sample the produce. Home-canned, smoked or fermented fish is also a risk. Recent outbreaks have been reported from commercial carrot juice and home-canned bamboo shoots. In the United States, roughly 100 people become ill with botulism each year. About a quarter are due to consumption of contaminated food. Most cases today (about 70%) occur in infants. Babies less than 1 year old, especially those that are breast feeding, have a different intestinal system than adults. Spores swallowed by an adult with a mature digestive tract usually will remain in their hibernating, inactive state. But spores ingested by a young infant can reproduce and can form toxin that is absorbed into the bloodstream, causing botulism.

In one out of five cases of botulism in infants, the infant has eaten raw honey. More rarely, botulism spores are found in corn syrup. Since the majority of cases of infant botulism can't be traced to a food source, experts suspect that babies are exposed simply by swallowing small amounts of dust or dirt.

Rarely, botulism is the result of a contaminated wound. Most wound botulism today occurs in people who inject or snort recreational drugs.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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