bubble_chart Overview

Botulism is a toxic disease caused by the exotoxin of Clostridium botulinum. It manifests in three clinical types: foodborne botulism, wound botulism, and infant botulism, all primarily characterized by neurological symptoms.

bubble_chart Epidemiology

(1) Source of Pestilence | Clostridium botulinum exists in the intestines of animals. After excretion, its spores can survive in soil for a considerable time, but it can only proliferate extensively under anaerobic conditions.

(2) Transmission Routes | ① Foodborne transmission: Canned foods, fermented steamed buns, homemade stinky tofu, and bean paste contaminated with Clostridium botulinum can cause illness due to their exotoxins. ② Occasionally, infection can occur through wounds. ③ The bacteria may sometimes contaminate foods like honey. When ingested by infants, the bacteria proliferate in the gastrointestinal tract, producing large amounts of exotoxins and causing illness, also known as infant botulism. Reports of such cases have been increasing abroad in recent years.

(3) Susceptibility | The exotoxin is highly pathogenic to both humans and animals. People of all ages and genders can contract the disease. Patients are not contagious (non-pestilential). {|102|}

bubble_chart Pathogen

Clostridium botulinum is a strictly anaerobic, gram-positive, spore-forming bacillus. Its spores exhibit extreme heat resistance, surviving in boiling water for 5 to 22 hours, and require 5 to 15 minutes of dry heat at 180°C to be killed. The spores can only be destroyed by 10% hydrochloric acid after 1 hour or 20% formaldehyde after 24 hours. This bacterium thrives in soil and is found in the feces of livestock such as cattle, sheep, and pigs, as well as on fruits, vegetables, and grains. When ham, sausages, canned, or bottled foods are contaminated with C. botulinum, the bacteria can proliferate extensively under anaerobic conditions, producing exotoxins that cause poisoning upon ingestion. Based on the antigenicity of the exotoxins, they are classified into seven types (A to G). Human diseases are primarily caused by types A, B, and E, occasionally by type F, while infant botulism is most commonly associated with types A and B. The botulinum exotoxin is a potent neurotoxin, with a minute dose of one-millionth of a milliliter capable of killing a 250g guinea pig within four days. However, it is heat-labile, being destroyed after 30 minutes at 80°C or 10 minutes of boiling, and rapidly loses its toxicity when exposed to sunlight. Under dry, sealed, and dark conditions, the toxin can remain potent for years. Both the toxin and its formaldehyde-treated toxoid are antigenic and can induce antitoxin production when injected into animals.

bubble_chart Pathogenesis

Botulinum exotoxin is absorbed through the stomach and the upper part of the small intestine, then transported via the lymphatic and circulatory systems to motor nerve synapses and cholinergic nerve terminals. It interferes with and blocks the neuromuscular junction, inhibiting the release of acetylcholine, thereby causing muscle paralysis. The central nervous system generally shows no significant involvement. Macroscopic and microscopic findings during autopsy are nonspecific.

Infant botulism occurs in children under 6 months of age. Infants ingest Clostridium botulinum spores or vegetative cells, which may not contain the exotoxin initially, but the bacteria can proliferate extensively in the infant's intestines and produce the exotoxin. Symptoms appear after the exotoxin is absorbed. In recent years, similar cases have been reported in adults abroad.

bubble_chart Clinical Manifestations

The incubation period is generally 1 to 2 days, with a maximum of 8 to 10 days. The shorter the incubation period, the more severe the illness.

The onset is sudden, with neurological symptoms as the main manifestation, which differs from general food poisoning. Initially, symptoms include general weakness, fatigue, headache, and vertigo, followed by drooping eyelids, dilated pupils, diplopia, strabismus, and paralysis of the intraocular and extraocular muscles. Severe cases may experience difficulty swallowing, chewing, speaking, and breathing, hoarseness or aphonia, difficulty raising the head, ataxia, and heart failure, though complete limb paralysis is rare. When the pharyngeal muscles are paralyzed, mucus secretions and abdominal mass in the throat may lead to aspiration pneumonia. Due to the blockade of cholinergic nerve transmission, symptoms such as abdominal distension and fullness, urinary retention, and reduced saliva and tear production may occur. Body temperature is normal or slightly elevated, consciousness remains clear, sensation is intact, and cerebrospinal fluid is normal.

Patients may gradually recover over several days (4 to 10 days), with difficulties in breathing, swallowing, and speaking improving first, followed by the gradual recovery of other muscle paralyses. Visual recovery is slower and may take several months. Severe cases may die within 3 to 10 days of onset due to respiratory failure, heart failure, or secondary pneumonia. The fatality rate for type E virus can reach 50%.

The clinical manifestations of infant botulism are not entirely the same as the symptoms described above. The first symptom is often constipation, followed rapidly by cranial nerve paralysis, with the condition progressing swiftly. Some infants may be able to eat and move freely before falling asleep, only to be found hours later with respiratory arrest. Others may present as a latent type or a fulminant type. Electromyography shows brief, low-amplitude, polyphasic action potentials, which aid in diagnosis.

bubble_chart Diagnosis

The main bases are: ① A history of ingesting suspicious food (especially canned food) and collective outbreaks among those who ate together; ② Typical clinical symptoms such as ocular muscle paralysis, difficulty swallowing, speaking, and breathing; ③ Bacteriological examination and animal inoculation tests on the suspicious food. The food extract can be orally administered (or intraperitoneally injected) to guinea pigs or mice. If exotoxin is present, the animals will exhibit typical limb paralysis and die. Exotoxin can be detected in the gastrointestinal contents of the affected individuals.

This disease should be differentiated from mushroom poisoning.

bubble_chart Treatment Measures

(1) Antitoxin Therapy Prompt administration of botulinum antitoxin is most effective when given within 24 hours of symptom onset or before paralysis occurs. Administer 50,000 to 80,000 units intravenously or intramuscularly in a single dose, repeating the injection after 6 hours if necessary. For severe cases, double the dose.

(2) Supportive and Symptomatic Treatment Upon initial diagnosis or suspicion of the disease, immediately perform gastric lavage with water or potassium permanganate (1:4000) and administer an enema. Patients should rest quietly in bed and stay warm. Use a suction device to remove secretions or abdominal masses from the throat. Provide oxygen for respiratory distress and initiate artificial respiration if necessary. For difficulty swallowing, use nasogastric feeding or intravenous drip. Administer appropriate antibiotics for secondary infections such as pneumonia. For wound botulism, thoroughly debride the wound and administer antitoxin. Pyridine can stimulate nerve sprouting and shorten the course of the disease. Guanidine hydrochloride promotes acetylcholine release at peripheral nerves and can also be used to treat botulism, though it is ineffective for severe respiratory failure.

Infant botulism primarily requires supportive and symptomatic treatment. Some advocate oral or intramuscular penicillin to reduce the intestinal load of Clostridium botulinum and prevent further production and absorption of exotoxin. Antitoxin is generally not used.

bubble_chart Prevention

Strictly manage food, paying special attention to the production of canned foods and the packaging and preservation of cured foods such as ham. Proper food disinfection is the key to preventing this disease. When Clostridium botulinum is present in food, phenomena such as gas production and odor changes often occur, but this is not always the case. Therefore, never taste suspicious food. Cans that bulge (swollen cans) or show changes in color, smell, or taste must be boiled before disposal and should not be used to feed livestock. Cured foods and homemade bottled foods should be boiled for 6 to 10 minutes before consumption. The consumption of fermented or spoiled foods is prohibited.

If someone who shared the same food exhibits symptoms of botulism, or if the food consumed contains Clostridium botulinum exotoxin, they should immediately receive polyvalent botulinum antitoxin serum (1000–2000 units) to prevent the onset of the disease.