Botulism--information from the world health organization. (Technical Briefs).

Overview

Human botulism is a serious but relatively rare disease caused by extremely potent toxins preformed in foods. The toxins are produced by the bacterium Clostridium botulinum. Person-to-person transmission of botulism does not occur. Seven recognized types of botulism are recognized. Four of these (types A, B, E, and, rarely, F) cause human botulism. Types C, D, and E cause illness in mammals, birds, and fish. The sporulated form of the bacterium is commonly found in soils, aquatic sediments, and fish. The spores are heat-resistant. Under anaerobic conditions, C. botulinum spores can germinate, and the bacterium can grow and produce the toxin. Ingestion of toxin present in improperly prepared food is dangerous and may be fatal. Botulism is mainly a foodborne intoxication, but it also can be contracted through wound infections or intestinal infection in infants.

Symptoms

The symptoms are not caused by the organism itself, but by the toxin that the bacterium releases. They usually appear within 12 to 36 hours after exposure (within a minimum-to-maximum range of four hours to eight days). Incidence of botulism is low, but the mortality rate is high if treatment is not immediate and proper. The disease can be fatal in 5 to 10 percent of cases.

The characteristic early symptoms and signs are marked fatigue, weakness, and vertigo, usually followed by blurred vision, dry mouth, and difficulty in swallowing and speaking. Vomiting, diarrhea, constipation, and abdominal swelling may occur. The disease can progress to weakness in the neck and arms, after which the respiratory muscles and muscles of the lower body are affected. The paralysis may make breathing difficult. There is no fever and no loss of consciousness. Similar symptoms usually appear in individuals who have shared the same food. Most victims recover if they receive proper and immediate treatment, including prompt diagnosis, early administration of antitoxin, and intensive respiratory care.

The seven types of intoxication due to the C. botulinum toxin are as follows:

1. Foodborne botulism occurs when the organism Clostridiwn bowlintim is allowed to grow and produce toxin in food that is then eaten without cooking sufficient to inactivate the toxin. Clostridium botulinwn is an anaerobic bacterium, which means it can grow only in the absence of oxygen. Therefore, the growth of the bacteria and the formation of the toxin tend to occur in products with low oxygen content and the right combination of storage temperature and preservative parameters. This combination occurs most often in lightly preserved foods such as fermented, salted, or smoked fish or meat products and in inadequately processed home-canned or home-bottled low-acid foods such as vegetables. Botulinal toxin has been found in a variety of foods, including low-acid preserved vegetables (e.g., green beans, spinach, mushrooms, and beets); fish (e.g., canned tuna and fermented, smoked, and salted fish); and meat products, (e.g., ham, chicken, and sausage). The foods traditionally implicated differ among countries, reflecting local eating habits and food preservation procedures. Occasionally, commercially prepared foods are involved. The toxin is destroyed by normal cooking processes (heating at >85[degrees]C for five minutes or boiling for a few minutes). Clostridium botulinum will not grow, and therefore the toxin will not be formed, in acidic foods (pH <4.6). Low pH will not, however, inactivate any preformed toxin.

2. Inhalation botulism, following inhalation of the toxin in aerosol form, has occurred in laboratory workers. In these cases, neurological symptoms may be the same as those of foodhorne botulism, but the incubation period may be longer.

3. Waterborne botulism theoretically could result from the ingestion of preformed toxin via water. Since water treatment processes inactivate the toxin, the risk is considered low.

4. Adverse effects of the pure toxin have been reported as a result of medical or cosmetic use in patients.

5. Infant botulism is a rare form of the disease, occurring when infants ingest spores, which germinate and produce bacteria that reproduce in the gut and release the toxin. In most adults and children older than about six months, this form of the disease does not occur because the natural defenses that develop over time prevent germination and growth of Clostridium bowlinum. Clinical symptoms of infant botulism include constipation, loss of appetite, weakness, an altered cry, and a striking loss of head control. Infant botulism has been associated with honey contaminated with botulism spores. Mothers are warned not to feed raw honey to their infants, as Clostridium botulintim spores in honey have in a few cases resulted in infant botulism.

6. Botulism of undetermined origin usually involves adult cases in which no food or wound source can be identified. It has been suggested that these cases are comparable to infant botulism and may occur when the normal gut flora have been altered as a result of surgical procedures or antibiotic therapy.

7. Wound botulism is a rare disease that occurs when spores get into an open wound and are able to reproduce in an anaerobic environment. The symptoms are similar to those of the foodborne form, but may take up to two weeks to appear.

Prevention

Prevention of botulism is based on good food preparation (particularly food preservation) practices and hygiene. Botulism may be prevented by inactivation of the bacterial spores in heat--sterilized, canned products and by inhibition of growth in all other products. Commercial heat pasteurization (vacuum-packed pasteurized products, hot-smoked products) may not be sufficient to kill all spores, and safety must therefore be based on prevention of growth and toxin production. Refrigeration temperatures combined with salt content, acidic conditions, or both, will prevent growth or formation of toxin.

If exposure to the toxin via an aerosol is suspected, it is important to prevent additional exposure to the patient and health care providers by removing the patient's clothing and storing it in plastic bags until it can be washed with soap and water. The patient must shower thoroughly.

Food and water samples associated with suspect cases must be obtained immediately, stored in proper sealed containers, and sent to reference laboratories to help prevent further cases.

Treatment

Antitoxin administration is indicated as soon as possible after clinical diagnosis has been made. Severe botulism cases necessitate supportive treatment, especially mechanical ventilation, which may be required for weeks or months. Antibiotics are not required (except in the case of wound botulism). There is a vaccine against botulism, but it is used very rarely as its effectiveness has not been fully evaluated and it has side effects.

Botox injections

The bacterium Clostridium botulinum is the same bacterium that is used to produce Botox, a pharmaceutical given as injections for clinical and cosmetic purposes. Purified and diluted A neurotoxin is used in Botox treatments. Treatment is administered in a medical setting, tailored according to the needs of the patient, and usually well tolerated. Occasionally there may be some side effects.

Readers can obtain World Health Organization (WHO) press releases, fact sheets, and feature articles, as well as further information on botulism, on the Internet at http://www.who.int/. (Adaptedfrorn WHO Fact Sheet No. 270, August 2002.)