OVERVIEW: What every practitioner needs to know

Are you sure your patient has botulism? What are the typical findings for this disease?

Adult-type botulism can be food borne or can be a result of wound contamination. Clinical features of foodborn botulism include the following:

Cranial nerve palsies (ptosis, blurry vision, mydriasis, dysarthria, dysphagia, dyphonia, ophthalmoplegia with diplopia)

Dry mouth

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Flaccid muscle paralysis (including respiratory muscles)

Gastrointestinal symptoms (nausea, vomiting, diarrhea, and later, constipation)

Wound botulism presents with the following clinical features:

Cranial nerve palsies (ptosis, blurry vision, mydriasis, dysarthria, dysphagia, dysphonia, ophthalmoplegia with diplopia)

Breathing difficulties (stridor, shortness of breath)

Flaccid muscle paralysis, typically in a descending (upper to lower extremity) pattern

Infant botulism presents as follows:


Poor suck and swallow reflex



Diffuse hypotonia and weakness

Shallow breathing; respiratory failure


What other disease/condition shares some of these symptoms?

Adult-type botulism must be distinguished from the following conditions:

Variants of Guillain-Barré syndrome (especially the Miller Fisher variant)

Electrolyte disturbances

Myasthenia gravis

Brainstem encephalitis

Drug reaction

Chemical intoxication


Other disorders causing bulbar dysfunction

Infant botulism may be confused with the following conditions:

Metabolic disorders, including mitochondrial disorders


Infections, either viral or bacterial

Spinal muscular atrophy

Electrolyte disturbances

Myasthenia gravis

What caused this disease to develop at this time?

Food-borne botulism results from ingestion of preformed toxin contained in
Clostridium botulinum–contaminated foods, especially home-canned, improperly sterlized, or spoiled foods. Botulinum toxin, a potent neurotoxin, binds irreversibly to presynaptic nerve endings, inhibits the release and transmission of acetylcholine, and causes neuromuscular paralysis.

Wound botulism results from localized infection with C. botulinum, which is sometimes derived by injecting contaminated drugs, and production of botulinum toxin that circulates to nerve endings.

Infant botulism results from ingestion of C. botulinum spores and production of botulinum toxin in the infant’s gastrointestinal tract. Toxin enters the bloodstream, circulates to nerve endings, and induces neuromuscular paralysis.

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

Routine laboratory studies are not helpful in diagnosing any form of botulism.

Food-borne botulism is diagnosed by detecting botulinum toxin in patient serum or stool or in implicated foods. Toxin can persist in a patient’s serum for up to 16 days after ingestion.

Toxin is detected by using a mouse bioassay and neutralization studies.

Wound botulism is diagnosed by isolating C. botulinum organisms from wounds using anaerobic culture methods and by detecting botulinum toxin in patient sera using a mouse bioassay and neutralization studies.

Infant botulism is diagnosed by detecting botulinum toxin in stool samples using a mouse bioassay and neutralization studies.

Would imaging studies be helpful? If so, which ones?

Neuroimaging studies have no role in diagnosing any form of botulism. However, certain conditions, such as stroke or brainstem encephalitis, that may mimic some symptoms or signs of adult-type botulism can be excluded by magnetic resonance imaging studies of the brain.

Neurophysiologic studies, using electromyography and nerve conduction testing, can be used to establish the diagnosis of adult-type or infant botulism. Electromyography may show reductions in compound muscle action potentials and incremental responses (facilitation) to repetitive stimulation at high (>20 Hz) frequencies. Nerve conduction velocity studies can be used to exclude conditions, such as variants of Guillain-Barré syndrome, that may mimic botulism.

Confirming the diagnosis

There are no algorithms currently used to diagnose botulism. However, botulism should be suspected in adults or infants with acute bulbar dysfunction.

If you are able to confirm that the patient has botulism, what treatment should be initiated?

Patients with adult-type botulism, whether food-borne or existing in a wound, require treatment with heptavalent botulism antitoxin available from the US Centers for Disease Control and Prevention. Antitoxin can be obtained by contacting state health departments in the United States. Antitoxin prevents progression of disease by binding with circulating toxin, indicating that administration of antitoxin when botulism is suspected has the greatest benefit for adults with botulism. However, antitoxin does not reverse signs or symptoms that are already present.

Infants with suspected or proven infant botulism require treatment with human botulism immune globulin (BabyBIG) available from the California State Department of Public Health. BabyBIG consists of pooled human immunoglobulin derived from individuals immunized with botulinum toxoid. Additional information can be obtained at www.infantbotulism.org. Like antitoxin, botulism immune globulin prevents progression of neuromuscular paralysis by binding with circulating toxin.

Antibiotics are not indicated for patients with botulism; aminoglycoside antibiotics can worsen neuromuscular paralysis.

What are the adverse effects associated with each treatment option?

Because the antitoxin used to treat adult-type botulism is derived from horse serum, approximately 10% of adult patients who receive botulism antitoxin experience allergic reactions consisting of serum sickness or, rarely, anaphylaxis. Before administering antitoxin, patients should undergo sensitivity skin testing.

BabyBIG, used to treat infant botulism, is associated with few side effects. However, as a human product, BabyBIG could induce allergic reactions.

What are the possible outcomes of botulism?

Approximately 5%-15% of cases of food-borne botulism result in death, usually from respiratory failure or delay in administering antitoxin. Patients with botulism require meticulous supportive care, often including mechanical ventilation. Patients with adult-type botulism may require mechanical ventilation for extended periods. Recovery is usually complete.

Approximately 2% or fewer cases of infant botulism result in death. Infants with botulism recover completely, although the course of recovery can be protracted. Like patients with adult-type botulism, infants with botulism may require mechanical ventilation and tube feedings for extended periods.

What causes this disease and how frequent is it?

Approximately two to three outbreaks and 20 cases of food-borne botulism occur annually in the United States. In highly endemic areas, such as among indigenous Alaskans, the annual incidence may be as high as six cases/100,000 persons.

Approximately 70 cases of infant botulism occur annually in the United States. Cases are commonly observed in California, Pennsylvania, and Utah. C. botulinum type B predominates among cases in the Eastern United States, whereas type A predominates among cases in the Western United States.

Wound botulism occurs worldwide but is rare. Cases are associated with massive tissue trauma and with injection of drugs, especially black tar heroin.

Botulism, whether adult type or infant, results from the toxin produced by the spore-forming, anaerobic bacterium C. botulinum.

Adult-type botulism can occur at any age: the average age is 40-50 years and patients with drug-associated wound botulism are often in their 20s and 30s. Infant botulism can occur between the ages of 1 week and 15 months; most cases occur between 3 and 5 months of age.

Foodborne botulism results from consumption of improperly preserved or stored food that is contaminated with botulinum toxin. In anaerobic conditions, C. botulinum spores contained in these foodstuffs germinate and produce botulinum toxin.

Wound botulism results from localized infection with C. botulinum and production of toxin under anaerobic conditions. Infant botulism results from ingestion of
C. botulinum spores and production of toxin in the infant’s gut.

No genetic factors are known to predispose individuals to adult-type or infant botulism.

How do these pathogens/genes/exposures cause the disease?

Botulism, both adult type and infant, results from the neurotoxin produced by the spore-forming, anaerobic bacterium, C. botulinum. The bacterium grows in anaerobic conditions, such as in improperly preserved foods or in wounds, and produces toxin. When ingested, produced in tissues, or produced in the infant’s gut, the botulinum toxin, the most potent known human neurotoxin, disseminates through the circulation to the synaptic vesicles, where it binds irreversibly and prevents release of the neurotransmitter acetylcholine. The failure of acetylcholine release induces neuromuscular paralysis, especially of bulbar muscles.

What complications might you expect from the disease or treatment of the disease?

Potential complications of either adult-type or infant botulism include paralysis, respiratory failure, and death. Fortunately, death is uncommon with supportive care, including mechanical ventilation and enteral or parenteral nutrition, and early administration of antitoxin in adult-type cases.

How can botulism be prevented?

Food-borne botulism can be prevented by proper sterilization of home-canned foods and by boiling foods for 10 minutes or more before consumption.

Wound botulism associated with drug use can be prevented by avoiding drug injection.

Some cases of infant botulism can be prevented by not giving infants certain foods, such as honey, that can be contaminated with C. botulinum spores. However, most cases of infant botulism cannot be prevented, given the ubiquitous nature of C. botulinum spores.

What is the evidence?

Evidence for antitoxin in the treatment of adult-type botulism, whether food-borne or present in a wound, remains anecdotal. Nonetheless, treatment is indicated in suspected or proven cases, given the association between improved recovery and early administration of botulism antitoxin.

Use of BabyBIG is supported by a single randomized trial that indicated that the duration of hospitalization, mechanical ventilation, and tube or parenteral feedings were significantly reduced in infants who received BabyBIG.

Arnon, SS, Schechter, R, Maslanka, SE. “Human botulism immune globulin for the treatment of infant botulism”. N Engl J Med. vol. 354. 2006. pp. 462-71. (This randomized trial demonstrated that treatment with BabyBIG significantly shortened hospitalization for infants with botulism.)

Thompson, JA, Filloux, FM, Van Orman, CB. “Infant botulism in the age of botulism immune globulin”. Neurology. vol. 64. 2005. pp. 2029-32. (This retrospective review of a single center's experience describes the clinical features of infant botulism and the impact of botulism immune globulin.)

Ongoing controversies regarding etiology, diagnosis, treatment

There remains some controversy regarding the cost-benefit ratio of BabyBIG administration. BabyBIG is very expensive; its major benefit is a reduction in the length of hospitalization and the duration of mechanical ventilation in ventilated infants.