Botulism is a specific and often fatal type of food poisoning that results from ingestion of toxin produced by Clostridium botulinum. The clinical illness is characterized by variable gastrointestinal complaints, dilated and nonreactive pupils, dryness of the oral mucous membranes, and progressive muscle weakness.
Etiology.
Six strains of C. botulinum, designated types A, B, C, D, E, and F, have been described. Each type produces an antigenically distinct toxin. Types A, B, and E are responsible for most human disease. Only two outbreaks of type F botulism have been reported, one in Denmark and one in California. Types C and D produce disease limited almost entirely to animals.
Botulinum spores are distributed in soil throughout the world. Type spores are common in the western United States, whereas B spores are found in the eastern United States and in Europe. Type E spores are associated with northern latitudes, often being isolated from lake-shore mud, coastal sand, and sea-bottom silt. The intestinal tracts of fish are often contaminated with type E spores, accounting for the high incidence of type E strains observed in fish-borne botulism. Type F spores have been found in marine sediments off the California and Oregon coasts and in salmon from the Columbia River. The spores are heat-resistant and have remained viable after exposure to 100° C. for several hours. However, exposure to moist heat at 120° C. for 30 minutes will kill spores of all six types.
Botulinum toxins have been identified as proteins and are the most potent poisons known. They are less heat-stable than the spores, all toxins being destroyed by boiling for 10 minutes or by exposure to 80° C. for 30 minutes.
Pathogenesis.
Human botulism results ingestion of preformed botulinum toxin in laminated foods. A large variety of home processed foods have been implicated in outbreaks of botulism in the United States. Commercially proc products have been involved on only a few sions. Relatively anaerobic environments and peratures above 80c F. provide the best cond for toxin production. However, a strictly anae atmosphere is not necessary, and some strains have produced toxin at temperature low as 6° C. (42.8° F.). Food contaminated-v, and B botulinum strains may often appear sp because of the Proterozoic enzymes produce! these micro-organisms. However, many type strains do not elaborate these enzymes, so foods containing type E toxin may appear taste perfectly normal.
Botulinum toxin is primarily absorbed from upper gastrointestinal tract, but toxin reach the lower small bowel and colon may be absorbed, thus perhaps accounting for the del onset and prolonged duration of symptoms in many patients with clinical botulism.
Botulinum toxins block transmission in cholinergic nerve fibers. Neural impulses are interrupted close to the terminations of nerve fib but short of the motor end plate, thus prevent’ acetylcholine release. Muscle reactivity to ace choline remains intact. The toxins may h some effect on the central nervous system.
Clinical. Manifestations.
Clinical illness vary from mild indisposition that requires medical attention to rapidly fatal disease minating in death within 24 hours. Characteristically, symptoms begin 12 to 36 hours after ingestion of the contaminated food. Nausea vomiting may be severe with type E disease, are less frequently observed in patients w type A or B intoxication. Weakness, lassitude, dizziness are often early complaints. Sever dryness of the mouth and pharynx, occasiona’ associated with pharyngeal pain, is also not’ Neurologic symptoms may occur early in course or may be delayed for 12 to 72 hours. These include blurred vision, diplopia, dysphonia dysphagia, and muscle weakness. Difficulty breathing accompanies respiratory muscle involvement. Constipation and abdominal distention may be prominent complaints.
Mentation remains intact and fever is observed in uncomplicated cases. Difficulties articulation and swallowing are often seen; the pupils are dilated and fixed; and extraocular p: sies may be observed. The mucous membranes the mouth and pharynx are often dry, crusted, ar. erythematous. Weakness of muscle groups particularly of the neck, proximal extremities, a respiratory musculature, is often observed the disease progresses, but superficial and deep? tendon reflexes remain intact. Abdominal distention and absence of bowel sounds may be noted. and urinary retention may occur. Sudden respiratory paralysis and airway obstruction may develop, and, together with secondary infection, these are the major causes of death.
Diagnosis.
The full-blown clinical syndrome of botulism in a group of people having ingested a home-canned product is readily recognized: on the other hand, diagnosis in an isolated case may be extremely. difficult. The neurologic diseases most frequently confused with botulism are myasthenia gravis, acute poliomyelitis. Guillaume Barre syndrome, and stroke. A negative Tensilon test for myasthenia gravis, normal cerebrospinal fluid, absence of sensory involvement, preservation of deep tendon reflexes, mentative clarity, and absence of corticospinal tract signs in patients with botulism help in the differential diagnosis.
Other non-neurologic disorders have been confused with botulism. Pharyngeal pain, erythema, and dysphagia have sometimes suggested streptococcal or viral pharyngitis. The dry mouth and mucous membranes and dilated pupils resemble signs observed in atropine, belladonna, or Simson weed poisoning. The mentative clarity, absence of central nervous system excitement, and the delay in appearance of symptoms observed in botulism help exclude these possibilities. Nausea, vomiting, and abdominal distention, together with constipation and ileum, have led to the mistaken diagnosis of intestinal obstruction. The neurologic signs observed in botulism should help exclude this diagnosis.
Circulating toxin may occasionally be detected by injecting the patient’s serum into mice. Fresh serum should be injected intraperitoneally in 1 ml. amounts, with and without the addition of types A, B, E, and F antisera. If toxin is present animals injected with serum alone may die, although mice protected with specific antiserum will survive. Portions of any suspected food should be suspended in saline and injected into mice in the same fashion, and should be cultured for anaerobic bacilli.
Treatment.
Most patients with botulism die of respiratory failure; thus, early tracheostomy and utilization of a tank respirator or other mechanical aid to respiration may be life-saving. Cleansing enema should be given to remove any reabsorbed toxin from the colon. As soon as the clinical diagnosis of botulism has been made, patients should be skin-tested for serum sensitivity, If they are negative, two vials of trivalent A, B, E botulinum antitoxin should be administered. This dose may be repeated in two to four hours.
This preparation of antitoxin can be obtained from the U.S. National Communicable Disease Center by calling 404-633-3311 by day or 404-634-2561 by night. Bivalent A, B antitoxin, manufactured by Lederer Laboratories, is still available but should be given only to patients known to have type A or B botulism, or if a considerable delay in obtaining the trivalent preparation is anticipated. A small supply of type F antitoxin is also available from the National Communicable Disease Center. No cross protection between antitoxins exists. Patients sensitive to horse serum should be desensitized before antitoxin is given. If available. antitoxin in one-third to one half the therapeutic dose may be given prophylactically to those who are known to have eaten the contaminated food but who have not yet developed symptoms.
Although many reports in the literature have indicated that antitoxin does not alter the course of type A botulism once symptoms have developed, reduction in mortality in several type E outbreaks by utilization of antiserum has been impressive. This suggests that the efficacy of antitoxin in ali types f botulism be re-evaluated.
Prognosis
Mortality from type A botulism has generally beer. high, running between 60 and 70 per cent. The fatality rate with type B disease has been lower, ranging between 10 and 30 per cent. Type E botulism has produced mortality rates ranging from 3 L 5 per cent in large series. With prompt diagnosis, vigorous management of respiratory paralysis, and prompt administration of polyvalent antitoxin, it is likely that these mortality figures can be considerably improved. If a patient survives the severe paralytic illness, recovery is usually rapid, and complete return to health can be anticipated.
