█ BRIAN HOYLE
Botulinum toxin is among the most poisonous substances known. The toxin, which can be ingested or inhaled, and which disrupts transmission of nerve impulses to muscles, is naturally produced by the bacterium Clostridium botulinum . Certain strains of C. baratii and C. butyricum can also be capable of producing the toxin.
Botulinum toxin has become well known in recent years for two reasons. First, the toxin has become a weapon in the arsenal of terrorists. Contamination of food is one route for infection with the toxin. The toxin can also be released into the air, which was attempted on at least three occasions between 1990 and 1995 by the Japanese cult Aum Shinrikyo. The government of Iraq admitted to United Nations inspectors following the 1991 Persian Gulf War that tens of thousands of liters of botulism toxin had been produced and loaded into weapons. The toxin was the most numerous of all the biological weapons then developed by Iraq.
Paradoxically, the other reason for the toxin's fame is the use of the toxin as a cosmetic enhancement (i.e., "botox").
There are at least seven structurally different versions of botulinum toxin. The type designated as type A is responsible for some food-borne outbreaks in the United States and elsewhere. Improperly canned foods are a particular threat.
Clostridium botulinum is a spore-forming bacterium. Like the well-known anthrax bacillus, the spores of Clostridium botulinum can persist in the environment for many years and, when conditions become more favorable (i.e., in a wound, food, and the lungs) the spore can germinate and free the toxin. Dried preparations of the spores can thus represent a terrorist weapon.
The use of botulinum toxin as a weapon began in the 1930s, with experiments conducted by the Japanese on prisoners during the occupation of Manchuria. In World War II, plans were made to vaccinate Allied troops participating in the D-day invasion of Normandy, because of concerns that Germany had weaponized the toxin. Even the United States maintained an active biological weapons program, including the use of botulism toxin, into the late 1960s.
Botulism toxin acts by preventing the transmission of nerve signals between the nerves that connect with muscle cells. Progressive functional deterioration of the affected muscles occurs. Symptoms of botulism intoxication include dizziness, blurred or double vision, nausea, vomiting, diarrhea, and weakness of muscles in various areas of the body. The muscle failure can be so severe as to lead to coma and respiratory arrest. Even in those who survive exposure to the toxin, complete recovery can take months.
█ FURTHER READING:
Tucker, J.B., (ed.). Toxic Terror: Assessing the Terrorist Use of Chemical and Biological Weapons. Cambridge: MIT Press, 2000.
Byrne, M.P., and L.A. Smith. "Development of Vaccines for Prevention of Botulism." Biochimie no. 82 (2000): 955–966.
Kahn, A.S., S. Morse, and S. Lillibridge. "Public-health Prepardness for Biological Terrorism in the USA." Lancet no. 356 (2000): 1179–1182.
Montecucco, C. (ed.). "Clostridial Neurotoxins: The Molecular Pathogenesis of Tetanus and Botulism." Current Topics in Microbiology and Immunology no. 195 (1995): 1–278.
Lacy, D.B., W. Tepp, A.C. Cohen, et al. "Crystal Structure of Botulinum Neurotoxin Type A and Implications for Toxicity." Nature Structural Biology no. 5 (1998): 898–902.
Centers for Disease Control and Prevention. "Botulism." Public Health Emergency Preparedness and Response. February 7, 2003. < http://www.bt.cdc.gov/agent/botulism/index.asp >(April 15, 2003).
Johns Hopkins University. "Botulinum Toxin." Center for Civilian Biodefense Strategies. 2002. < http://www.hopkins-biodefense.org/pages/agents/agentbotox.html >(April 15, 2003).