Botulism is a life-threatening illness characterized by muscle paralysis and variable gastrointestinal symptoms. It is caused by absorption from the gastrointestinal tract of ingested toxin produced by Clostridium botulmum. Botulism resulting from wound infection by this organism has also been recorded several times.
Incidence of Botulism.
The unexpectedness of outbreaks of botulism, the dramatic and frightening nature of the illness, and its high mortality have attracted much attention from both laymen and doctors, but botulism is in fact an uncommon disease. From 1899 to 1969 there were 659 outbreaks in the United Staten, with 1696 cases and 959 death Outbreak- have also recorded in many other countries, especially in Canada, Japan, Western Europe, Scandinavia, and the U.S.S K.
Epidemiology of Botulism.
The six strains of Cl bolulinum cause disease in man and in a variety of animals. Human disease is caused by types A. B. and E and occasionally by type F Toxins produced by the different types are an-tigenically distinct. Cl. botultnum. A pore-bedring anaerobic bacillus, is widely distributed in nature The organism has been identified in many parts of the world, in cultivated and virgin soils, in a variety of marine environment*, and m many animals and animal products. The distribution of types varies in different art-.i’ so that type A botulism is more common than type B in the United States, especially in the Western states, whereas in Europe this order is reversed. In recent years type E has superseded both types A and B in frequency Type E organisms are especially but not exclusively associated with the aquatic environment in northern latitudes, being found in the sea bed of coastal and lake waters and in the intestinal tract of fish However, types A and B may also be associated with a marine source.
Pathogenesis of Botulism.
Contamination of fresh food by spores of Cl bolulinum does not cause botulism The spores must have germinated and toxin must have been produced by the vegetative organisms. Spores are destroyed at a temperature of 121® C or greater, as used in commercial canning processes, but can usually survive a temperature of 100′ (’. Type E upores are relatively heat sensitive, but smoking and light cooking may not kill them, so that food processed in these ways or preserved in the raw slate may act as a vehicle of the disease. Another factor predisposing to type E botulism is the production of toxin by this organism at temperatures as low as 5* C. The cooking or preserving process is conducive to the germination of spores and. by reason of the lowered redox potential, to multiplication of the vegetative forms Multiplication is inhibited in acid media, and botulism is rarely associated with food of pH below 4.5. All types of botulinum toxin are heat labile, and botulism could be entirely prevented by terminal heating for 20 minutes at 80* C and for 10 minutes at 90 * c.
The type of food associated with botulism as a result of these contributory factors vary, with local food customs. from country to country. In the United States home-preserved vegetables constitute the most frequent source, followed by preserved fruit and fish products. Meat and meat products are more commonly responsible in Europe Preserved fish is the chief sou rev of botulism in .Japan, Scandinavia, and the U S S K Although most outbreaks are associated with domestic methods of preparing and preserving foods, outbreaks from commercially prepared foods also occur. Recent sources have included canned tuna fish, canned vtchyssoise. and vacuum-packed smoked fish Ingested toxin is rapidly absorbed from the gastrointestinal tract. Toxemia may be demonstrated for periods of up to ten days or even three weeks, and it is possible that toxin continues to be absorbed from the bowel for some days after ingestion. Type E toxin is potentiated by proteolytic enzymes, including trypsin, and this phenomenon has been invoked as a mechanism which contribute-‘ to the pathogenicity of this type Botulinum toxin is active in extremely low doses, nanogram quantities nf pure toxin being let hal to mice It prevents conduction in peripheral nerves by a proiynaptic block, thus preventing release of acetylcholine without direct action on the acetylcholine release mechanism Anticholinesterase drugs do not affect, its action.
Clinical Manifestation of Botulism.
Illness usually begins between 12 and 36 hours after ingesting the toxin-containing food The first manifestations are often gastrointes-tinal. especially in type E disease, with nausea, vomiting, abdominal pain, and distention Other common early symptoms are weakness, unsteadiness, and dryness of the mouth and throat Neurologic symptoms may uccompany the early gastrointestinal illness or may follow at an interval of 12 to 72 hours. Early features are blurring of vision, dysphagia, dysarthria, and weakness of u variety of muscles Weakness spreads as the disease advances, affecting especially the respiratory system, the external ocular muscles, and muscles of the neck and proximal limb groups.
The pupils are usually dilated and fixed, and retention of urine is common Deep tendon reflexes are preserved. The patient remains mentally clear, and fever is not observed except as a terminal event Paralysis may continue for many day* or weeks One recent outbreak of type A botulism showed atypical features; the pupill.it • tiol remained normal, and two of the six patients showed myasthenic features not usuully observed in botulism Defects of cardiac conduction have occasionally been noted.
The chief causes of death are respiratory or bulbar paralysis or both, along with the ineffective complications resulting from these paralyses Diagnosis The illness is easily recognized if a group of patients, known to have eaten food of a type associated with botulism, present with characteristic symptoms. By-contrast. diagnosis of the individual patient, in whom there may be no suspicion that the illness is a form of food poisoning, has often proved extremely difficult. The gastrointestinal features may he so severe as to simulate intestinal obstruction, and the epigastric pain may be mistaken for that of myocardial infarction. The dry and sometimes painful throat may suggest various forms of acute pharyngitis, and the combination of sore throat and neurologic disease can cause confusion with diphtheria. The neurologic illness has been mistaken for acute polyneuritis iGuillain-Barre syndrome), encephalitis, a stroke, or myasthenia gravis. The dry mouth and fixed dilated pupils suggest atropine poisoning, as is produced by Datura stramonium tjimson weed’ Paralytic poison.
The illness is easily recognized if a group of patients, known to have eaten food of a type associated with botulism, present with characteristic symptoms. By-contrast. diagnosis of the individual patient, in whom there may be no suspicion that the illness is a form of food poisoning, has often proved extremely difficult. The gastrointestinal features may he so severe as to simulate intestinal obstruction, and the epigastric pain may be mistaken for that of myocardial infarction. The dry and sometimes painful throat may suggest various forms of acute pharyngitis, and the combination of sore throat and neurologic disease can cause confusion with diphtheria. The neurologic illness has been mistaken for acute poly-neuritis iGuillain-Barre syndrome), encephalitis, a stroke, or myasthenia gravis. The dry mouth and fixed dilated pupils suggest atropine poisoning, as is produced by Datura stramonium tjimson weed). Paralytic poisoning caused by shellfish or by puffer fish isee belowi is accompanied by prominent sensory symptoms not found in botulism.
Circulating toxin may sometimes be detected in the patient’s blood, even long after onset of the disease. It is detected by intraperitoneal injection in mice, controls simultaneously receiving antiserum of the different types Suspected food is also tested for toxin in the same way. and the organism is sought by anaerobic culture.Suspected food is also tested lor toxin in the Mine way. and the organism is sought by anaerobic culture.
Treatment of Botulism.
Since the greatest risk of botulism is respiratory failure, treatment is dominated by the prevention and management of this complication Bulbar paralysis is treated by early tracheostomy, employing a cufTed endotracheal tube. Coincident or supervening respiratory muscle paralysis indicates the need for artificial ventilation applied through the tracheostomy Specific antitoxin is probably effective in reducing the mortalitv of type E botulism Although there is no such evidence in Other forms of botulism, the high mortality of the disease and the difficulty of obtaining statistically valid data justify the use of antitoxin in all forms of the disease Antitoxin should be given irrespective of the duration of illness when the diagnosis is made, because toxin maybe present in the blood for many days. Unless the type of botulism is definitely known, multivalent antitoxin should be administered, because the type cannot be reliably inferred from the food source.
After a prelimi-nary test for hypersensitivity to horse serum, two vials of tnvalent antitoxin >each containing 7500 IU type A, 5500 IU type B. and 8500 IU type E antitoxin) art administered by intravenous injection, and this is repeated in two to four hours. For botulism of known type, preparations containing A and B antitoxin or E antitoxin alone are available, as is a small stock of monovalent P antitoxin
Until 1968 no method had been proposed by which the effects of botulinum toxin could be counteracted, hut recently guanidine hus been cluuned as a useful adjunct in treatment Both clinical and electromyographic improvement were observed in a number of patients who received guanidine by nasogastric tube in a dose of 15 to 50 mg per kilogram per day.
Since it is uncertain whether the long duration of toxemia in botulism is attributable to continued absorption from the bowel, gastric aspiration and colonic washouts are also used in treatment. A solution of sodium bicarbonate may he left in the stomach to promote breakdown of toxin
The over-all mortality of botulism is high, 60 to 70 per cent for type A. 10 to 30 per cent for type B, and 30 to 50 per cent for type E. Patients with type E botulism tend to die more quickly than those affected by other types, usually within three days of onset. Improved management of respiratory failure should lower the death rate, especially because patients who survive the stage of severe paralysis can recover completely.