Botulism
Botulism is caused by the ingestion of food containing the neurotoxin (toxin that affects the nervous system) produced by Clostridium botulinum, an anaerobic spore forming bacterium. Sixty to seventy per sent cases of botulism die. There are 7 types (type A,B,C,D,E,F,G) of these neurotoxins recognised on the basis of specificity. The neurotoxin of C.botulinum is a protein. It has been purified and crystallized and is so powerful that only a dose as low as 0.01 mg is said to be fatal to human beings. The toxin is absorbed mostly in the small intestine and paralyzes the involuntary muscles of the body.

Source.
The main sources of botulism are canned meat, fish, string beans, sweet corn, beans, and other low medium acid foods. The foods implicated are generally those of a type that have undergone some treatment intended for the preservation of the product such as canning, pickling or smoking, but one which failed to destroy the spores of this bacterium. When the intended preservative treatment is inadequate and is followed by storage conditions which permit the germination and growth of the microorganisms, one of the most lethal toxins known to humanity is produced. The toxin has been known to persist in foods for long periods, especially when storage has been at low temperatures. It is unstable at pH value above 6.8.

Prevention. Canned food should be properly processed by using approved heat processes. Food that has been cooked but not well heated should be avoided. Raw foods and frozen foods thawed and held at room temperature should be avoided. Gassy and spoiled canned foods should be rejected. Boiling of suspected food for at  least 15 minutes is required.

Treatment. Successful treatment is by the administration of polyvalent antitoxin in the early stages of infection. Once the symptoms appear the treatment fails to prove useful.