Foodborne botulism is a serious, potentially fatal, but relatively rare disease. This is intoxication, usually caused by the consumption of highly active neurotoxins, botulinum toxins formed in contaminated foods. Botulism is not transmitted from person to person.
The spores produced by Clostridium botulinum are resistant to high temperatures and are widespread in the environment. In the absence of oxygen, these spores germinate, develop and begin to secrete toxins. There are 7 different forms of botulinum toxin – types A – G. Four of them (types A, B, E and in rare cases F) cause human botulism. Types C, D, and E cause disease in mammals, birds, and fish.
Botulinum toxins enter the body through the consumption of products that have not undergone proper processing, in which bacteria or spores survive and produce toxins. The main cause of human botulism is food intoxication, but it can be caused by intestinal infection in infants, wound infections, and inhalation.
Symptoms of foodborne botulism
Botulinum toxins are neurotoxic and therefore have an effect on the nervous system. Foodborne botulism is characterized by downward flaccid paralysis, which can lead to respiratory failure.
Early symptoms include severe fatigue, weakness, and dizziness, usually followed by blurred vision, dry mouth, and difficulty swallowing and speaking. Vomiting, diarrhea, constipation and bloating may also occur. As the disease progresses, weakness may appear in the neck and arms, after which the respiratory muscles and muscles of the lower body are affected. The temperature does not rise and loss of consciousness does not occur.
The cause of these symptoms is not the bacterium itself, but the toxin produced by it. Symptoms usually appear 12–36 hours later (at least 4 hours and at most 8 days) after exposure. The incidence of botulism is low, but the mortality rate is high if the correct diagnosis is not quickly made and treatment is immediately provided (administration of antitoxin in the early stages and intensive mechanical ventilation). The disease can be fatal in 5–10% of cases.
Exposure and transmission
C. botulinum is an anaerobic bacterium – this means that it can develop only in the absence of oxygen. Foodborne botulism develops when C. botulinum bacteria grow and produce toxins in foods before they are consumed. C. botulinum produces spores that are widespread in the environment, including soil, as well as river and sea water.
Bacterial growth and toxin production occur in products with a low oxygen content and with a certain combination of storage temperature and preservation parameters. Most often this occurs in foods of easy preservation, as well as in products that have not undergone proper processing, canned or bottled at home. In an acidic environment (pH less than 4.6), C. botulinum does not develop, and therefore, toxin is not produced in acidic products (however, a low pH does not destroy the toxins produced earlier). To prevent bacterial growth and toxin production, low storage temperatures are also used in combination with certain levels of salt and / or acidity.
Botulinum toxin is found in a wide range of foods, including low acid canned vegetables, such as green beans, spinach, mushrooms and beets; fish such as canned tuna, fermented, salted and smoked fish; and meat products such as ham and sausages. Food products vary from country to country and reflect local food patterns and food preservation practices. Sometimes botulinum toxins are found in industrial products.
Although C. botulinum spores are resistant to high temperatures, the toxin produced by bacteria that develop from spores under anaerobic conditions breaks down when boiled (for example, at an inside temperature> 85C for five or more minutes). Therefore, most often the cause of human botulism is ready-to-eat products in packages with a low oxygen content.
To find out the cause and prevent further cases of the disease, it is necessary to immediately obtain samples of products involved in the alleged cases of the disease, place them in appropriate hermetically sealed containers and send to the laboratory.
Infant botulism develops mainly in children under the age of 6 months. Unlike foodborne botulism caused by the consumption of already developed toxins in foods (see paragraph “a” above), childhood botulism develops when children swallow C. botulinum spores, from which bacteria colonizing the intestines and secreting toxins develop.