Botulism is a very dangerous infectious disease, which is caused by food contaminated with Clostridium botulinum, a harmful bacterium that secrets botulin. Botulin is a very toxic enzyme, which affects the central nervous system. Thus, it produces difficulty in swallowing, visual disturbances, and respiratory paralysis. This disease, which is characterized by paralysis and other neurological abnormalities, is often fatal. Botulin is found in canned food and fish, and it causes paralysis by preventing nerve cells from releasing acetylcholine at the neuromuscular junctions. Botulism is found in all parts of the world but more often in countries where the population uses many home-canned products.
Cause
The causative agent of botulism is a spore-forming rod-shaped bacterium, which is called Clostridium botulinum. This microorganism belongs to the group of anaerobic bacteria. There are six types of causative agents of botulism —A, B, C, D, E, and F— each of which produces a specific exotoxin which affects the nervous system. Like the spore of Clostridium tetani, which causes tetanus, the spores of the causative agent of botulism are found in soil, from which they enter water and food products (fodder), and through them, the intestines of man and animals; they multiply in the intestines and are then dispersed on the earth’s surface in feces.
Disease and Clinical Picture
Man is infected with botulism when the Clostridium botulinum and its toxins enter the digestive tract with food. Infection occurs through canned meat and fish (with unsanitary conditions of animal slaughter and processing of carcasses), vegetables, fruits, and canned mushrooms that have not been subjected to proper processing and sterilization. The toxin absorbed in the intestine circulates in the blood and affects the nuclei of the cranial nerves and of intracardial nerve ganglia. The incubation period—from the moment of infection to the appearance of the first symptoms of disease—varies from two hours to ten days; it is usually 18–24 hours.
Botulism begins suddenly with the onset of weakness, frequent repeated vomiting, and constipation; the stomach is often distended. Body temperature may be slightly elevated or remain normal. After 3–4 hours dizziness appears, vision is disturbed; the patient sees all objects as though in a fog; there is often double vision and strabismus. The patient’s mouth feels dry and he is thirsty; swallowing food and even water becomes difficult; breathing disturbances are possible. Speech becomes indistinct and the voice very weak. Sometimes convulsions are observed. Death may result from paralysis of the heart or respiratory center.
A reliable diagnosis of botulism is made upon discovery of the toxins or microbes in the blood, vomitus, and so on of the patient. He must be hospitalized as soon as possible because it is an emergency situation. Treatment requires specific antitoxic serum and artificial ventilation of the lungs in respiratory disturbances due to paralysis of the intercostal muscles of the ribcage, which are voluntary muscles located between each pair of adjacent ribs. When contracted, the external intercostal muscles raises the ribcage upward and outward to increase the volume of the chest, causing air to be forced into the lungs. Thus, when the central nervous system is affected by botulin and there is paralysis of these muscles, there is a failure of the mechanics of respiration and the patient requires artificial ventilation. Prophylaxis of botulism calls for the observance of sanitary hygienic rules in the preparation of canned foods and in the processing, transportation, and storage of raw foods.
Botulism in animals is food poisoning characterized by paralysis of the pharyngeal musculature, tongue, and lower jaw. Horses, poultry, less frequently cattle, and, among fur bearers, mink are susceptible to botulism. Spores of the causative agent, entering fodder from the soil, germinate under favorable conditions. The botulism toxin, entering the intestine with fodder, is absorbed in the body. Treatment in the initial stage requires purgatives -for instance, arecoline, pilocarpine, and physostigmine- and at a later stage by heart medicines. Prophylaxis calls for the observance of hygiene in the feeding of animals. When the disease occurs on animal-breeding farms, the healthy population is vaccinated.
 |
| Above, in blue, Clostridium botulinum bacteria. |