Colorado State University Extension
SafeFood Rapid Response Network
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Botulinum Toxin: Friend or Foe
Edited by: Mary Schroeder, M.S., R.D. & Pat Kendall, Ph.D., R.D., Colorado State - Summer 2005
Botulinum Toxin is most commonly associated with Botulism, a paralytic illness caused by neurotoxins of the anaerobic, spore-forming bacterium, Clostridium botulinum, an organism found in soil throughout the world. The canning and fermentation of foods are particularly conducive to creating anaerobic conditions that allow C. botulinum spores to germinate. Botulism was first described in the 18th century among those who consumed sausages. Commercially canned foods caused outbreaks in the 19th and 20th centuries before standard methods for inactivating C. botulinum spores in cans were perfected. While outbreaks related to commercially canned foods are now quite rare, improperly prepared home canned and fermented foods, as well as foods served in restaurants, account for a large proportion of U.S. botulism cases. Traditional Alaskan Native foods, especially fermented foods eaten without cooking, pose a risk and account for the high incidence of botulism in Alaska.
Of the seven antigenic toxin types (A-G) identified, types A, B, E and occasionally F are associated with human disease. Studies in the U.S. have shown that spores producing toxin type A predominate west of the Rockies, while type B spores are more predominant in the East. Type E spores are usually associated with the marine environment. Illness caused by toxin type A tends to be more severe and associated with a higher fatality rate.
Treatment
Botulinum toxin causes paralysis by binding (irreversibly) to receptors on nerve endings, entering the nerve, and interfering with the release of acetylcholine, causing flaccid paralysis. Symptoms begin with a dry mouth, sensation of a "thick tongue" and blurred vision, followed by descending weakness and paralysis, including the muscles of respiration. Recovery can take weeks to months, and may require ventilator support. The Centers for Disease Control and Prevention (CDC) is the only source of therapeutic antitoxin, which is stocked in locations around the country for rapid release.
Clinical Forms
In the United States, an average of 110 botulism cases is reported each year. Of these, approximately 25% are foodborne, 72% are intestinal botulism and the rest are wound botulism.
Foodborne botulism.
Home canned food items such as vegetables, meat, fish, relishes, salsas, foil-wrapped baked potatoes and garlic in oil have been implicated in outbreaks, resulting from the combination of low acid, low-salt, anaerobic conditions that allow spores to germinate, grow and produce the toxin. Symptoms usually begin within 12 to 36 hours of eating the contaminated food item. From 1990 to 2000, 160 foodborne botulism events afflicted 263 people in the United States. Due to the severity of this illness (5-10% fatality rate), it is imperative to follow tested food preservation methods to effectively destroy spores before they can germinate.
Intestinal botulism.
Formerly known as infant botulism because it usually occurs in infants less than 6 months old, this form of illness results from the colonization of C. botulinum in the gastrointestinal tract. The growing organisms produce toxins, which are absorbed in vivo. Although honey is a known risk factor, the source is most often unknown. In rare instances intestinal botulism can occur in adults with gastrointestinal tract abnormalities resulting from diseases like Crohn's or from gastrointestinal bypass surgery.
Wound botulism.
This form of botulism results from spore germination in an abscessed wound. Toxin is produced and absorbed at the site of infection. Although rare, the incidence of wound botulism associated with illicit drug use has increased in recent years.
Therapeutic and Cosmetic Uses
Since the 1980's, Botox®, a dilute concentration of toxin A or B, has successfully been used therapeutically to treat a number of muscle related medical conditions. Effects of a single toxin injection can last several months to a year. Under the trade name Botox®, the toxin has been approved for cosmetic use since 2002. Its effectiveness in smoothing out facial wrinkles (by paralyzing the underlying muscles) is keeping plastic surgeons busy. As reported in Cosmetic Surgery Times, April 2004, Botox® ranks #1 as the most popular of all surgical and non-surgical cosmetic procedures.
Bioterrorist Weapon?
Use of botulinum toxin as a bioweapon dates back to the 1930's when it was produced by the U.S. and Soviet Union in their biological weapons programs. In the 1990's, a Japanese cult ineffectively dispersed botulinum toxin on three occasions. Although it poses a real biosecurity threat, the toxin is difficult to stabilize and concentrate for aerosol dissemination. Heating food and water to an internal temperature of 85ºC (185ºF) for at least 5 minutes destroys any botulinum toxin (but not the spores) that may be present.
Because home and restaurant-prepared foods remain the leading causes of foodborne botulism in the United States, preventive measures must continue to incorporate culturally appropriate education materials regarding safe food handling and preservation processes. Additionally, it would be prudent for community emergency preparedness planners to include measures for dealing with the incidence of intentional botulism poisoning on a wide scale.
Sources:- Botulinum Toxin: From Botox to Bioterrorism. CD Summary. An Epidemiology Publication of the Oregon Department of Human Services. Aug. 10, 2004. Vol. 53, No. 16.
- J. Sobel, N. Tucker, A. Sulka, J. McLaughlin and S. Maslanka. Foodborne Botulism in the United States, 1990-2000. Emerging Infectious Diseases. http://www.cdc.gov/eid Vol.10, No.9, Sept. 2004. http://www.cdc.gov/ncidod/EID/vol10no9/03-0745.htm
