BOTULISM

poisoning by the toxin, called botulinus toxin, or botulin, produced by Clostridium botulinum bacteria. This poisoning results most frequently from the eating of improperly sterilized canned foods containing the toxin. C. botulinum bacteria cannot survive in the presence of oxygen and normally live in the soil, where they form heat-resistant spores that may contaminate fresh food to be canned. The spores survive if the food is not cooked at a high enough temperature for a sufficient length of time. Then, inside the sealed can, the spores germinate and release the bacteria, and, as the bacteria multiply, they secrete their toxin, a protein that is one of the most potent poisons known. Unlike the spores, the toxin is readily destroyed by heat; it remains potent if the contaminated food is not heated before it is eaten. Once ingested and absorbed, the toxin damages the autonomic nervous system by blocking the transmission of nerve impulses. The first symptoms of poisoning, nausea and vomiting, usually appear six hours or less after the contaminated food is eaten, depending upon the amount of toxin ingested. The poisoned person becomes tired and may complain of headache and dizziness. Often his vision is blurred, and he may see double. The mucous membranes of the throat may become dry; the affected person may feel a constriction in the throat, soon associated with difficulty in swallowing and speaking; and a general muscle weakness occurs. The respiratory muscles become involved. Early tracheotomythe cutting of an emergency air passage into the windpipeand the prompt use of mechanical aids to respiration may be lifesaving; about half the deaths from botulism result from paralysis of the respiratory muscles. Usually a person recovers completely if he survives the paralysis. With early diagnosis, the chance of a person's surviving is greatly enhanced by the prompt administration of botulism antitoxinssubstances that neutralize the toxin in the body. Often, however, the severe symptoms do not develop until the poison has already damaged the nervous system; at this stage, it is ordinarily too late for the antitoxins to be fully effective. Botulism most commonly originates with home-canned foods, rather than with foods that have been canned commercially.