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Public Health
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Epidemiology
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Infectious Disease
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Botulism
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Clinical Considerations
Hospital course and treatment Reporting and outbreak response Antitoxin use and clinical management Recovery
Initial presentation and evaluationBecause laboratory testing for botulism toxin takes at least several days, the initial diagnosis depends on accurate and rapid clinical assessment. A careful history often reveals recent consumption of traditional Alaska Native foods, particularly fermented foods. The incubation period, or interval from consumption of contaminated food to illness onset, varies but is usually 12-36 hours. Severely affected patients may have a more rapid onset (as short as 6 hours) and although unusual, incubation periods as long as 10 days have been described.The salient clinical features of botulism can be grouped into three major areas: gastrointestinal/urinary, neurologic, and muscular (Table 1).
a. Gastrointestinal/UrinaryGastrointestinal symptoms are usually the initial manifestations of botulism; however, they lack diagnostic specificity unless associated with other findings. Nausea, vomiting, diarrhea, and abdominal pain may be present initially or appear within 2-3 days of illness onset. The origin of these symptoms is not completely clear, but may be secondary to toxin induced intestinal ileus. Ileus is sometimes severe and relatively long lasting (i.e., more than 1 week). Urinary retention, presumably caused by detrusor weakness, is often present but frequently asymptomatic early in the course of the illness.b. NeurologicWhen the effects of cholinergic blockade are observed, the diagnosis of botulism must be seriously considered, especially in an Alaska Native patient with gastrointestinal symptoms. Dryness of oral mucous membranes may be extreme and can lead to fissuring of the tongue and severe pharyngeal pain. The "pharyngeal" presentation of botulism has been confused with diphtheria. Ocular findings are classic: diplopia, blurry vision, fixed or dilated pupils, and ptosis commonly are present. The absence of ocular findings does not rule out the diagnosis of botulism. However, the absence of any objective signs of cranial nerve weakness makes botulism extremely unlikely. The progressive paralysis typically descends, affecting the cranial nerves first, then the neck, upper arms, trunk and diaphragm, and finally the hands and legs. The fingers may be last affected.c. MuscularSkeletal muscle weakness, manifested by fatigue, shoulder, neck or truncal weakness, or dyspnea, is ominous. Because the muscles of respiration are weakened, typical signs of dyspnea such as gasping, vigorous chest motions or use of accessory muscles of respiration are usually absent. Precipitous deterioration of respiratory reserve with concomitant respiratory arrest has caused almost all of the early deaths from botulism and is not necessarily preceded by other complaints. Often a patient's paralysis prevents demonstration of agitation or restlessness, so they may appear to be resting comfortably. It is imperative that respiratory reserve be assessed and followed diligently. Measurement of forced vital capacity (FVC) should be sufficient to indicate the degree of respiratory compromise and is a convenient index to follow for signs of deterioration.Knowledge of findings that should be normal in botulism may be helpful in establishing or ruling out the diagnosis. Body temperature, orientation to person, place and time, sensory examination, and deep tendon reflexes (if the patient is not completely paralyzed), should all be normal. Rare exceptions have occurred and even if signs or symptoms not usually associated with botulism are present, clinicians may still need to consider botulism in the differential diagnosis, especially if other findings are suggestive. The differential diagnosis of botulism (Table 2) generally involves consideration of rare conditions or unusual presentations of common problems, such as stroke. It is often best to pursue a diagnosis of botulism, perhaps in parallel with others, until the diagnosis is clear, particularly if the patient is an Alaska Native who has consumed fermented food during the week before onset of symptoms. Laboratory data from electromyography, nerve conduction studies, cerebrospinal fluid analysis, or Tensilon® testing are more helpful for diagnosing other conditions than for establishing the diagnosis of botulism. Occasionally an electromyogram will show convincing post-tetanic potentiation which is almost specific for botulism. Cerebrospinal fluid and nerve conduction studies should be normal in patients with botulism.
Several reports have suggested that if three or more signs or symptoms in a "diagnostic pentad" are present, and a patient has a history of consuming traditional Alaska Native food, botulism should be strongly suspected (Table 3). Neither the sensitivity nor specificity of this method is 100% and all relevant clinical information should be considered when deciding if a patient might have botulism. The following "clinical paradigm" is probably more sensitive but less specific than the diagnostic pentad:
Botulism should be considered in any patient having a history of consumption of traditional Alaska Native food with:
Neither of these approaches have been rigorously tested, but both have been found useful by clinicians experienced in the diagnosis of botulism in Alaska. Either approach may help trigger suspicion of botulism.
Hospital course and treatmentSince the laboratory bioassay for botulism toxin usually takes at least 48 hours, the results are not useful for the immediate management of patients, but can be very helpful in corroborating the diagnosis. Samples of serum, vomitus or gastric aspirate, suspect food(s), and stool should be collected for analysis. Serum should be obtained prior to the administration of antitoxin. Arrangements for testing will be handled by the Alaska Division of Public Health, Section of Epidemiology.The most urgent clinical concern for the patient suspected of having botulism is assessment of respiratory reserve. Most patients will require frequent (at least hourly initially) determination of FVC or an equivalent measure. Any significant decline in respiratory function should prompt consideration of endotracheal intubation and assisted ventilation. For patients in an outlying hospital requiring transfer for management of respiratory insufficiency, placement of endotracheal and nasogastric tubes should be strongly considered prior to transfer. 
Reporting and outbreak responseBotulism is both a medical and public health emergency. If a health care provider suspects botulism, he or she should immediately notify the Alaska Division of Public Health, Section of Epidemiology so that possible associated cases can be identified and treated. Reporting should never await laboratory confirmation. Delayed reporting may result in additional people consuming toxin-containing food and additional cases of botulism. The Section of Epidemiology investigates all botulism cases in the state (Table 4).Possible cases should be reported by telephone to the Section of Epidemiology in Anchorage at 1-907-269-8000. For after hours reporting, an epidemiologist can be reached through the Section of Epidemiology answering service at 1-800-478-0084. Medical epidemiologists from the Section are available 24 hours a day to provide clinical consultation and advice regarding diagnosis, specimen collection, and treatment.
Antitoxin use and clinical managementIn Alaska, most rural hospitals serving Alaska Native patients, as well as the Alaska Native Medical Center in Anchorage, have equine trivalent (A,B,E) antitoxin in their pharmacies. Directions for allergic sensitivity testing are included with the vial and should be followed; there has been one documented case of a hypersensitivity reaction following administration in Alaska, and serum sickness or anaphylaxis have been reported elsewhere with antitoxin use.Botulism antitoxin acts by blocking attachment of circulating toxin to presynaptic acetylcholine release sites; it does not "neutralize" toxin or reverse the effect of toxin already bound to presynaptic sites. One vial of antitoxin provides more than a 100-fold greater than needed concentration of antitoxin for treating the highest level of circulating toxin ever detected at the U.S. Centers for Disease Control and Prevention (Hatheway, Snyder, and Seals 1984). Thus, intravenous administration of a single vial of botulism antitoxin is recommended immediately upon diagnosis (after serum has been collected) in all but the most mild suspected cases of foodborne botulism. Approximately a third of patients in one series (Barrett 1991) had continuing neurologic and muscular deterioration after receiving antitoxin and close observation of all patients must be maintained after treatment. Descriptions of foodborne botulism often emphasize the long duration of toxin effect (St. Louis 1991). Alaska Natives with botulism have had a remarkably more benign course, generally with rapid and complete recovery (Barrett 1991). Most patients requiring intubation and mechanical ventilation can be successfully weaned within days. Tracheostomy should not be seriously considered since the duration of paralysis is short. Patients with moderate to severe symptoms are prone to develop intestinal ileus and urinary retention. Ileus is of concern because retained gastric secretions may be aspirated and decreased intestinal motility may allow continued absorption of toxin. Nasogastric tube drainage is often useful to decompress the stomach and high colonic enemas encourage removal of retained colonic contents which may contain toxin. Urinary retention is a concern in every case of botulism and, if present, is best managed by catheterization. Nosocomial infection complicates the recovery of many severely affected patients; fever is the cardinal sign since botulism toxin itself does not provoke fever. Pneumonia is the most frequent complication and appears to be due to a variety of factors including reduced gag reflex, highly inspissated respiratory secretions, atelectasis associated with low tidal volumes, and aspiration of pharyngeal or gastric secretions due to paralysis or weakness. Protection of the airway, high environmental humidity, adequate lung expansion, and use of mucolytic agents may all help to reduce pulmonary infection. Urinary infections also occur and are probably related to urinary catheter use.
Recovery
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Nausea or vomiting
It is important for health care providers of a completely paralyzed patient to remember that the person is fully awake. The illness, procedures, and medical routines should be explained with recognition that the patient is conscious. Physicians should provide appropriate pain control and sedation for intubated patients who are otherwise alert. Patients can have excellent recall for events and conversations heard during total paralysis.
