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Trichothecenes

Dateline: 04/05/99

By Alan Bruzel

Fungi are noteworthy for their prominent roles in cheese-making, antibiotic production, and infectious disease. Roquefort, cephalosporin, and ringworm provide examples. They are also quite adept at synthesizing lethal compounds used in chemical and biological warfare (CBW).

Fungi from the genus Fusarium, growing on barley, corn, oats, rye, or wheat, produce dozens of derivatives of tetracyclic sesquiterpenes called trichothecenes. The best known of these are nivalenol, deoxynivalenol, diacetoxyscirpenol, and T-2 toxin. Bread inadvertently made from Fusarium-infected wheat killed thousands of Russian civilians after World War II, focusing attention on the chemistry of the trichothecenes. Fungi apparently use trichothecenes to enhance their infective attack on their plant hosts. These fungal virulence factors also easily lend themselves to military applications.

Nivalenol	Deoxynivalenol (Vomitoxin)

Diacetoxyscirpenol	T2 toxin

Trichothecenes are an attractive warfare agent because they may enter the body either by way of the skin, by inhalation, or by ingestion. If used, trichothecenes would be deployed in an aerosol. (Military use of the trichothecene-containing "yellow rain" in Laos and Kampuchea in the late 1970's has not been substantiated.) Preparation requires no great chemical wizardry. Fusarium fungi growing on cereal grains perform the complicated biosynthetic reactions involved in synthesizing the trichothecenes; the chemist simply isolates these mycotoxins. The adult LD₅₀ (lethal dose to 50% of exposed individuals) of trichothecenes is estimated to be only 35 milligrams.

Vomiting and bleeding – an effective means of incapacitating troops and civilians – result from mild mycotoxicosis. Severe poisoning leads to a protracted death. There are no antidotes; protective clothing and gas masks offer the only defense. These heat- and ultraviolet light-stable compounds, easily made and capable of long-term storage, are therefore superb candidates for stockpiling. Not surprisingly, United Nations Special Commission inspectors have established the presence of trichothecenes (and other CBW agents) in Iraqi facilities.

Recommended Web resources for additional information:

Chronic Sequelae of Foodborne Disease
Pathogens, their toxins, and their long-term effects. From James A. Lindsay, University of Florida at Gainesville.

Mycotoxins and Mycotoxicoses
Economically important food-contaminating agents produced by fungi. From Alabama A & M and Auburn Universities.

Reduced Virulence of Trichothecene-Nonproducing Mutants of Gibberella zeae in Wheat Field Tests
Role of trichothecenes in wheat head scab. Abstract provided by the American Phytopathological Society.

Threat of Deliberate Disease in the 21st Century
Details of chemical and biological weapon stockpiling. From Graham S. Pearson, University of Bradford.

Use of Chemical Weapons: Conducting an Investigation Using Survey Epidemiology
Yellow rain in Laos and Kampuchea not due to a warfare chemical. Reprint from the Journal of the American Medical Association provided by Physicians for Human Rights.

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