Botulism

Botulism (ichthyism, allantiism; English botulism, allantiasis, sausage-poisoning; French botulisme. allantiasis; German Botulismus Wurst-Vergiftung, Fleischvergtftung) is a neuromuscular poisoning caused by a toxin produced by Clostridium botulinum. Infection is not necessary for the development of this disease; it is enough to simply consume the toxin. Symptoms of botulism include muscle weakness and paralysis. Diagnosis of the disease is based on clinical and laboratory identification of the toxin. Treatment of botulism consists of clinical support and the use of antitoxin.

What causes botulism?

Botulism is caused by Clostridium botulinum, which releases seven types of neurotoxins, each with different antigens, four of which (types A, B, and E, and rarely F) are capable of infecting humans. Types A and B toxins are potent poisons. They are proteins that cannot be broken down by gastrointestinal enzymes. About 50% of foodborne outbreaks of botulism in the United States are caused by type A toxin, followed by toxins B and E. Type A toxin is found primarily west of the Mississippi, type B toxin in the eastern United States, and toxin E in Alaska and the Great Lakes region (Superior, Huron, Michigan, Erie, Ontario; Canada and the United States).

Botulism can occur in 3 forms: foodborne botulism, wound botulism, and infant botulism. In foodborne botulism, the toxin is absorbed through ingestion of contaminated food. In wound botulism and infant botulism, the neurotoxin is released in vivo in the infected tissue and colon, respectively. Once absorbed, the toxin inhibits the release of acetylcholine from peripheral nerve endings.

Clostridium botulinum spores are highly resistant to high temperatures. They can remain viable after boiling for several hours. They are killed by exposure to a humid environment at 120 C for 30 minutes. On the other hand, toxins are quickly destroyed by high temperatures, so cooking at 80 °C for 30 minutes is a reliable protection against botulism. Toxin production (especially toxin type E) can occur at low temperatures, around 3 °C, i.e. in a refrigerator, and MO does not require strict anaerobic conditions.

The most common source of botulism is home-canned foods, but about 10% of outbreaks involve commercially canned foods. The most common sources of the toxin are vegetables, fish, fruits, and condiments, but beef, dairy, pork, poultry, and other foods can also be contaminated. In seafood outbreaks, 50% of cases involve type E toxin, with the remaining 50% being type A and B toxins. In recent years, restaurant outbreaks of botulism have emerged that have been caused by uncanned foods such as potatoes baked in foil, processed cheese sandwiches, and chopped garlic fried in oil.

Clostridium botulinum spores are commonly found in the natural environment, and many cases may be due to inhalation of dust or absorption from the eyes or skin lesions. Infant botulism most commonly occurs in infants younger than 6 months. The youngest known patient was 2 weeks old and the oldest was 12 months old. Infant botulism results from ingestion of spores, which then colonize the large intestine where they begin to produce the toxin in vivo. Unlike foodborne botulism, infant botulism is not due to ingestion of pre-formed toxin. In most cases of infant botulism, the source of infection cannot be determined, although honey has been identified as the source of the spores in some cases.

What are the symptoms of botulism?

Foodborne botulism has a sudden onset, usually 18 to 36 hours after toxin ingestion, although the incubation period can range from 4 to 8 days. Nausea, vomiting, abdominal cramping, and diarrhea often precede neurologic symptoms. Neurologic symptoms of botulism are usually bilateral and symmetrical, beginning with cranial nerve involvement followed by descending muscle weakness and paralysis. Common initial symptoms of botulism include dry mouth, double vision, ptosis, impaired accommodation, and decreased or lost pupillary reflex. Symptoms of bulbar paresis (eg, dysarthria, dysphagia, dysphonia, and fixed facial expression) develop. Dysphagia may lead to aspiration pneumonia. Respiratory muscles and muscles of the extremities and trunk progressively weaken from above downward. In this case, no sensory impairment develops. There is no fever, the pulse rate is normal or slightly reduced. These indicators change only in the case of intercurrent infection. Constipation often develops after the appearance of neurological symptoms. Serious complications of botulism include acute respiratory failure due to paralysis of the diaphragm and lung infections.

Wound botulism, like food botulism, presents with neurological symptoms, but there are no gastrointestinal symptoms or evidence of ingestion of contaminated food. A history of traumatic injury or deep puncture wound within 2 weeks of onset of symptoms may suggest botulism. A thorough physical examination should be performed to detect skin lesions or abscesses associated with illicit drug use.

In infant botulism, constipation is the initial symptom in 90% of cases, followed by neuromuscular paralysis, beginning with the cranial nerves and continuing with the respiratory and peripheral muscles. Cranial nerve deficits typically manifest as ptosis, paresis of the extraocular muscles, weak crying, poor sucking, decreased sucking reflex, accumulation of oral secretions, and an expressionless facial expression. The severity of the disease varies from mild lethargy and poor nutrition to acute hypotension and respiratory failure.

How is botulism diagnosed?

Botulism may be mistaken for Guillain-Barré syndrome, poliomyelitis, myasthenia gravis, tick paralysis, and poisoning caused by the alkaloids curare and belladonna. In most cases, electromyography reveals a characteristic delayed response to rapid repetitive stimulation.

In foodborne botulism, the sequence of neuromuscular abnormalities and a history of ingestion of a suspect food are important diagnostic findings. Simultaneous identification of two patients who ate the same food simplifies the diagnosis. The diagnosis is confirmed by detection of toxin in serum or stool or by culture of the botulism material from stool. Detection of toxin in the suspect food establishes the source of poisoning.

In wound botulism, detection of toxin in serum or anaerobic culture of MO from the wound confirms the diagnosis.

Infant botulism may be mistaken for sepsis, congenital muscular dystrophy, spinal muscular atrophy, hypothyroidism, and benign congenital hypotonia. Finding Clostridium botulinum toxin or the organism in the stool makes the diagnosis obvious.

How is botulism treated?

All persons known or suspected to have eaten contaminated food should be carefully evaluated for botulism. Administration of activated charcoal may be helpful. Patients with severe symptoms often have impaired respiratory reflexes, so when charcoal is administered, a gastric tube should be used and the airway should be protected with a rubber-cuffed endotracheal tube. Vaccination with toxoids may be considered for persons working with Clostridium botulinum or its toxins.

Respiratory distress and its complications pose the greatest threat to life. Patients should be hospitalized and constantly monitored for certain indicators of viability. Progressive paralysis prevents patients from showing signs of respiratory distress, while their viability declines. Respiratory distress requires treatment of the patient in an intensive care unit, where intubation and mechanical ventilation are available. The use of such measures allows to reduce mortality to less than 10%.

Nasogastric intubation is the preferred method of artificial nutrition because it simplifies the delivery of calories and fluids. It also stimulates intestinal peristalsis, which eliminates Clostridium botulinum from the intestine. It also allows infants to be fed breast milk. It also avoids infectious and vascular complications that might otherwise arise with intravenous nutrition.

Trivalent antitoxin (A, B, and E) is available from disease surveillance and prevention centers. The antitoxin does not neutralize toxin that has already bound to the neuromuscular junction, so existing neurologic damage may not be quickly reversed. Complete recovery depends on the rate of regeneration of the nerve endings, which may take weeks or even months. However, the antitoxin may slow or stop further progression of the disease. Antitoxin should be given as soon as possible after clinical diagnosis and should not be delayed pending culture results. If antitoxin is given more than 72 hours after the onset of symptoms, it is unlikely to be effective. Equine trivalent antitoxin is used in the United States. It is given as a single 10 ml dose. Each dose contains 7,500 IU of antitoxin A, 5,500 IU of antitoxin B, and 8,500 IU of antitoxin E. All patients requiring antitoxin should be reported to the center's disease surveillance and prevention directors. Since the antitoxin is derived from horse serum, there is a risk of anaphylactic shock or serum sickness in the recipient. The use of equine antitoxin is not recommended in infants. The use of botulinum immune globulin (derived from the plasma of people immunized with Clostridium botulinum toxoid) in infants is under study.

Because even minute amounts of Clostridium botulinum toxin can cause serious illness, all materials suspected of being contaminated with the toxin require special handling. Details regarding specimen collection and handling may be obtained from state health departments or the Centers for Disease Control and Prevention.

How to prevent botulism?

Botulism can be prevented by proper canning and adequate cooking of canned foods before consumption. Spoiled canned foods and those that show signs of bloating should be discarded. Infants under 12 months of age should not be given honey as it may contain Clostridium botulinum spores.