Botulism is a disease caused by exposure to botulinum toxin produced from Clostridium species, mainly Clostridium botulinum. Clinical forms of the disease include foodborne, inhalational, wound, infant, adult intestinal toxemia, and iatrogenic. C. botulinum is a gram-positive, strictly anaerobic, spore-forming bacillus naturally found in soil and aquatic sediments. There are seven types of the toxin based on antigenic differences, labeled A through G. Types A, B, and E (and rarely, F) are pathogenic in humans. Types C, D, and E cause illness in other mammals, birds, and fish. Botulinum toxin lacks color, odor, and taste and is the most lethal toxin known. Death is caused by doses of less than 1 μg. Antibiotics have no activity against the toxin itself.
In response to unfavorable environmental conditions (changes in pH, temperature, and water or nutrient availability), C. botulinum bacteria “sporulate.” C. botulinum spores are hardy, resistant to desiccation, heat, ultraviolet (UV) light, and alcohols, and can survive boiling for up to 4 hours; however, they are readily killed by chlorine-based disinfectants. Once spores encounter more favorable conditions, such as are found in human tissues, they “germinate,” producing growing cells that are capable of reproducing and elaborating toxin.
The Working Group for Civilian Biodefense considers botulism to be a dangerous potential biological weapon because of the pathogen's “extreme potency and lethality; its ease of production, transport, and misuse; and the need for prolonged intensive care among affected persons.”