German physicians first identified botulism in the 18th century when patients developed an often fatal disease after eating spoiled sausage. Five distinct clinical syndromes are now recognized: food-borne botulism, infant botulism, wound botulism, adult intestinal colonization, and iatrogenic botulism. Inhalational botulism remains a theoretical risk. Food-borne botulism results from ingestion of preformed toxin in improperly preserved home-canned vegetables, fish, or meats. In the last few decades, noncanned foods have also been reported to cause food-borne botulism. Examples include fresh garlic in olive oil, sautéed onions, beef or turkey pot pie, baked potatoes, potato salad, smoked or fermented fish, turkey loaf, untreated well water, home-fermented tofu, turkey stuffing, and “pruno” (an alcoholic beverage illicitly brewed in prison settings).

1. Botulism is caused by a heat-labile neurotoxin (botulinum) produced by the bacterium Clostridium botulinum. Different strains of the bacterium produce eight distinct exotoxins: A, B, C, D, E, F, G and H; types A, B, E, and F are most frequently involved in human disease. Botulinum toxin irreversibly binds to cholinergic nerve terminals and prevents acetylcholine release from the axon. Severe muscle weakness results, and death is caused by respiratory failure. Symptom onset is variable. The toxin does not cross the blood-brain barrier.
2. Botulinum spores are ubiquitous in nature, and except in infants (and in rare situations adults), the ingestion of spores is harmless. However, in an anaerobic environment with a pH above 4.6, the spores germinate and produce botulinum toxin. The spores are relatively heat-stable but can be destroyed by pressure cooking at a temperature of at least 120°C (250°F) for 30 minutes. The toxin is heat-labile and can be destroyed by boiling at 100°C (212°F) for 10 minutes or heating at 80°C (176°F) for 20 minutes. Longer times are required at higher altitudes. Nitrites added to meats and canned foods inhibit the growth of clostridia. Foods contaminated with serotypes A and B often smell putrid.

Botulinum toxin is extremely potent; as little as one taste of botulinum-contaminated food (approximately 0.05 mcg of toxin) may be fatal.

1. Classic food-borne botulism occurs after ingestion of preformed toxin in contaminated food. Initial symptoms are nonspecific and may include nausea, vomiting, dry or sore throat, and abdominal discomfort. The onset of neurologic symptoms is typically delayed 12-36 hours but may vary from a few hours to as long as 8 days. The earlier the onset of symptoms, the more severe the illness. Diplopia, ptosis, sluggishly reactive pupils, dysarthria, dysphagia, dysphonia, and other cranial nerve weaknesses occur, followed by progressive symmetric descending paralysis. The patient's mentation remains clear, and there is no sensory loss. Pupils may be either dilated and unreactive or normal. Constipation and ileus resulting from decreased motility may occur. Deep tendon reflexes are reduced but often still present. Profound weakness involving the respiratory muscles may cause respiratory failure and death.
2. Infant botulism, the most commonly reported type, is caused by ingestion of botulism spores followed by in vivo production of toxin (typically type A or B) in the immature infant gut. Risk factors include age younger than 1 year, breastfeeding, and ingestion of corn syrup or honey (which commonly contains botulism spores). The illness is characterized by insidious onset of hypotonia, constipation, tachycardia, difficulty in feeding, poor head control, and diminished gag, sucking, and swallowing reflexes. With treatment, it is rarely fatal, and infants usually recover strength within 4-6 weeks.
3. Wound botulism occurs when the spores contaminate a wound, germinate in the anaerobic environment, and produce toxin in vivo that is absorbed systemically, resulting in illness. It occurs most commonly in intravenous drug users who “skin pop” (inject the drug subcutaneously), particularly those using “black tar” heroin. It has also been reported rarely with open fractures, dental abscesses, lacerations, puncture wounds, gunshot wounds, and sinusitis. The clinical manifestations are similar to those of food-borne botulism, although nausea and vomiting are usually absent and fever may be present. Manifestations of botulism occur after an incubation period of 1-3 weeks.
4. Adult intestinal colonization botulism occurs rarely in adults after ingestion of botulism spores. As in infant botulism, spores germinate in the intestinal tract, and the toxin is produced in vivo. Conditions predisposing patients to this rare form of botulism include a history of extensive gastrointestinal surgery, decreased gastric or bile acids, ileus, and prolonged antibiotic therapy altering intestinal flora. The onset of symptoms can be as late as 2 months after exposure.
5. Iatrogenic botulism occurs following the injection of botulinum toxin (type A or B) formulations FDA-approved for cosmetic purposes or the treatment of blepharospasm, strabismus, cervical dystonia, limb spasticity, chronic migraine, or axillary hyperhidrosis. Reported complications include muscle weakness, diplopia, asthenia, dysphagia, dyspnea, and stridor. Symptom onset is expected within 1-2 days of exposure and may persist for months.
6. Inhalational botulism remains a potential threat from terrorist groups, although no known attacks have successfully used aerosolized toxin. The inhaled form may be 100 times more potent than ingested toxin. Onset of symptoms may be more rapid and effects more lethal, potentially related to resource scarcity in a mass casualty scenario.

Is based on a high index of suspicion in any patient with a dry sore throat, clinical findings of descending cranial nerve palsies, and a history of exposure (eg, ingestion of home-canned food, IV drug use, or recent treatment with botulinum toxin type). Botulinum toxin testing should be performed, but results are usually delayed by at least 24 hours. In the appropriate clinical setting, treatment should not be postponed while awaiting test results. Electromyography (EMG) findings may help to differentiate botulism from other causes of weakness but should not be relied upon for diagnosis. The differential diagnosis includes myasthenia gravis, Eaton-Lambert syndrome, the Miller-Fisher variant of Guillain-Barré syndrome, hypermagnesemia, paralytic shellfish poisoning, and tick-related paralysis (eg, Dermacentor andersoni).

1. Specific levels. Diagnosis is confirmed by determination of the toxin in serum, stool, gastric aspirate, or a wound. Obtain serum, stool, wound pus, vomitus, and gastric contents, and suspect food for toxin analysis by the local or state health department. Microbiological test results may be negative owing to toxin levels below the level of detection or improper sample collection or storage. Samples should be taken prior to the administration of antitoxin.
2. Other useful laboratory studies include electrolytes, blood sugar, arterial blood gases, and electromyography.

1. Emergency and supportive measures
   1. Maintain an open airway and assist ventilation if necessary. Patients with a vital capacity of less than 20 mL/kg or a negative inspiratory force (NIF) worse than -30 cm H₂O are likely to require intubation and ventilatory support.
   2. Close monitoring of respiratory status with end-tidal CO₂ monitoring, continuous pulse oximetry, serial venous blood gases along with repeat NIF measurements should be performed as respiratory arrest can occur abruptly.
2. Specific drugs and antidotes
   1. Food-borne, wound, adult intestinal colonization, and iatrogenic botulism
      1. Botulinum antitoxin binds the circulating free toxin and prevents the progression of illness; however, it does not reverse established neurologic manifestations. It is most effective when given within 24 hours of the onset of symptoms.Contact the local or state health department or the Centers for Disease Control in Atlanta, Georgia, telephone 1-770-488-7100 (24-hour number), to obtain antitoxin. Antitoxin is not stocked by hospital pharmacies.
      2. For wound botulism, prompt wound debridement is imperative. Antibiotics (eg. penicillin) should be administered but are not sufficient in lieu of wound debridement. Aminoglycosides, fluoroquinolones, and clindamycin should be avoided because they may exacerbate neuromuscular blockade.
   2. Infant botulism
      1. BabyBIG (Botulism Immune Globulin Intravenous [Human] [page 503]) is indicated for the treatment of infant botulism caused by toxin type A or B in patients younger than 1 year of age. To inquire about obtaining BabyBIG, contact the Centers for Disease Control in Atlanta, Georgia, telephone 1-770-488-7100. In California, contact the state Department of Health Services, telephone 1-510-231-7600.
      2. Antibiotics are not recommended except for the treatment of secondary infections. Cathartics are not recommended.
3. Decontamination. Administer activated charcoal orally for food-borne botulism if conditions are appropriate (see Table I-37).
4. Enhanced elimination. There is no role for enhanced elimination; the toxin binds rapidly to nerve endings, and any free toxin can be readily detoxified with antitoxin.