Dear Doctors Column

August 20, 2007

Botulism: A Serious Illness Usually Caused by Home-Canned Foods

Question:

What’s behind the recent outbreak of botulism in canned foods? What are the symptoms of this kind of food poisoning?

Answer:

Concerns that certain brands of canned food might contain botulinum toxin, a nerve toxin caused by the germ Clostridium botulinum, recently prompted two large recalls: one of canned hot dog chili sauce and other canned items made by Castleberry Food Company (click here for complete list) and a second, just weeks later, of french cut green beans manufactured by Lakeside Foods, Inc.

In July four people were sickened and hospitalized with botulism poisoning after eating Castleberry’s Hot Dog Chili Sauce. The Food and Drug Administration (FDA) said they believe the company failed to properly cook some products, which allowed the C botulinum germs to survive the canning process. The company that makes the suspect green beans noted a problem with the cans’ vacuum seal, alerted the FDA, and recalled 15,000 cases of its canned green beans. As of August 16, the FDA had no reported no cases of illness linked to the green beans. The FDA says the two incidents are unrelated.

The nerve toxin produced by the C botulinum germ attacks the body’s nervous system and can cause paralysis and death. Symptoms include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness. Symptoms typically appear 18 to 36 hours after eating contaminated food, but can begin within 6 hours or up to 10 days later. Botulism poisoning is a medical emergency – if you develop symptoms seek medical attention immediately.

Botulism poisoning from commercially canned food is rare, according to the Centers for Disease Control and Prevention (CDC). Most of the 25 or so cases of foodborne botulism reported annually to the CDC are caused by contaminated home-canned foods — the organization reports that the last US case linked to commercially canned products was in the 1970s.

During the canning process food must be heated to a high enough temperature for a sufficient time to kill bacteria. Contamination also can occur if the food is packaged improperly or in defective cans – bacteria can enter through leaky seams or faulty seals and grow.

If you have any of the recalled products, use extreme care when discarding. Don’t open or puncture any unopened cans. Botulinum toxin is extremely potent and even a small amount inhaled, swallowed, or absorbed through the eyes or tiny cuts in the skin can cause life-threatening illness. The CDC offers instructions for safely discarding suspect items.

If you home-can, you must take care to use the right equipment, ingredients, and methods to produce safe, high quality products. Pressure canning, for example, is the only recommended technique for canning meat, poultry, seafood, and, vegetables. Although foodborne botulism is more often caused by home-canned foods with a low acid content such as asparagus, green beans, beets, and corn, there have been outbreaks of the poisoning from less-common sources such as garlic chopped in oil and improperly handled baked potatoes wrapped in aluminum foil (potatoes wrapped in foil should be kept hot until eaten or refrigerated).

Boiling food for 10 minutes destroys botulinum toxin, and the CDC advises that people take this precaution when eating home-canned foods. To learn more about home canning, visit the FDA’s “Complete Guide to Home Canning,” which also includes detailed recipes for fruits and fruit products, tomatoes and tomato products, vegetables, red meats, poultry, seafoods, and pickles and relishes.