Botulism

Botulism, poisoning caused mainly by eating food containing Clostridium botulinum, a poisonous bacterium. There are three main kinds of botulism. Food-borne botulism is caused by eating foods that contain the botulism toxin; wound botulism, by toxin produced from a wound infected with Clostridium botulinum; infant botulism, by consuming the spores of the botulinum bacteria, which then grow in the intestines and release toxin. All forms of botulism can be fatal and are medical emergencies. Food-borne botulism can be especially dangerous because a large number of people can be poisoned by eating a batch of contaminated food. The food-borne organism, which is derived from the soil, grows in many meats and vegetables. Its spores are killed by boiling for 30 minutes, but the toxins may be destroyed by moist heat at 80° C (176° F) for the same period. Because the spores grow best in the absence of oxygen, improperly processed foods in sealed containers offer a perfect environment for their development. Commercially prepared foods are now a rare source of the disease, but improperly sterilized home-canned non-acidic foods cause many cases. In the United States, for example, an average of 110 cases of botulism are reported each year. Of these, approximately 25 per cent are food-borne, 72 per cent are infant botulism, and the rest are wound botulism, which can occur in heroin addicts.

Symptoms usually appear 18 to 36 hours after ingestion. The toxin, which is not destroyed by the enzymes of the gastrointestinal tract, affects the central nervous system and interrupts nerve impulses, but the mind continues to function normally. Disability progresses from difficulty in walking and swallowing, along with impaired vision and speech, to occasional convulsions, and ultimately to paralysis of the respiratory muscles, suffocation, and death, all within a few hours or days, depending on the amount of toxin ingested. Two thirds of those attacked may die.

Tests may include a brain scan, spinal fluid examination, and a nerve conduction test (electromyography). The most direct way to confirm diagnosis is to demonstrate the botulinum toxin in the patient’s serum or stool by injecting serum or stool into mice and looking for signs of botulism. The bacteria can also be isolated from the stool of persons with food-borne and infant botulism.

Botulism antitoxin may be effective if administered early. Surgical opening of the trachea and use of a respirator may be life-saving. Physicians may try to remove contaminated food still in the gut by inducing vomiting or by using enemas. The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a ventilator for weeks. Research into the use of botulism in biological warfare has produced a toxoid, an inactivated poison for use in a vaccine, to induce immunity.