Clostridium botulinum is an anaerobic, Gram-positive, spore forming, rod shaped bacteria that produces the potent neurotoxin. The organism and its spores are widely distributed in nature and occur in both cultivated and forest soils, bottom of streams, lakes and coastal waters and in the intestinal tracts of fish and mammals and in viscera of shellfish.

On the basis of the serological specificity of their toxins, seven types of Clostridium botulinum are recognized: A, B, C, D, E, F and G. Types A, B, E, F and G cause disease in humans; type C causes botulism in fowls, cattle, mink and other animals and type D is associated with forage poisoning of cattle. Being a saprophyte, the organism seldom grows or produces toxin in the live animal; it can do so only by growing in food. The toxins are simple heat labile proteins and can be destroyed if heated at 80ºC for 10 minutes or longer.

C. botulinum does not produce the fully toxic molecule; instead a progenitor toxin is activated to its full toxicity by enzymes. The progenitor toxin is hydrolyzed to the highly toxic derivative toxin and is carried to target nerves where it binds to the synapses of motor neurons and prevents the release of the neurotransmitter acetylcholine. As a consequence, muscles do not contract in response to motor neuron activity and flaccid paralysis results.