Toxin produced by the bacteria when environmental conditions are favorable for the spores to replicate and grow, but the gene that encodes for the toxin protein is actually carried by a virus or phage that infects the bacteria.
Botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium Clostridium botulinum. The disease begins with weakness, blurred vision, feeling tired, and trouble speaking. This may then be followed by weakness of the arms, chest muscles, and legs. Vomiting, swelling of the abdomen, and diarrhea may also occur. The disease does not usually affect consciousness or cause a fever.
Botulism can be spread in several ways. The bacterial spores which cause it are common in both soil and water. They produce the botulinum toxin when exposed to low oxygen levels and certain temperatures.
Food-borne botulism happens when food containing the toxin is eaten.
Infant botulism happens when the bacteria develops in the intestines and releases the toxin. This typically only occurs in children fewer than six months old, as protective mechanisms develop after that time.
Wound botulism is found most often among those who inject street drugs. In this situation, spores enter a wound, and in the absence of oxygen, release the toxin. It is not passed directly between people.
Isolated cases of botulism have been described after inhalation by laboratory workers.
Human botulism is caused mainly by types A, B, E, and (rarely) F. Types C and D cause toxicity only in other animals.