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Botulism (from Latin botulus, "sausage") is a rare but serious paralytic illness caused by a nerve toxin, botulin, that is produced by the bacterium Clostridium botulinum. Botulin is the most potent known toxin, blocking nerve function and leading to respiratory and musculoskeletal paralysis. more...

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There are three main kinds of botulism:

  • Foodborne botulism is a form of foodborne illness and is caused by eating foods that contain the botulism toxin.
  • Wound botulism is caused by toxin produced from a wound infected with Clostridium botulinum.
  • Infant botulism is caused by consuming the spores of the botulinum bacteria, which then grow in the intestines and release toxin.

All forms of botulism can be fatal and are considered medical emergencies. Foodborne botulism can be especially dangerous as a public health problem because many people can be poisoned from a single contaminated food source.

In the United States an average of 110 cases of botulism are reported each year. Of these, approximately 25% are foodborne, 72% are infant botulism, and the rest are wound botulism. Outbreaks of foodborne botulism involving two or more persons occur during most years and usually are caused by eating contaminated home-canned foods. The number of cases of foodborne and infant botulism has changed little in recent years, but wound botulism has increased because of the use of black-tar heroin, especially in California.

Symptoms (foodborne and wound forms)

Classic symptoms of botulism occur between 12-36 hours after consuming the botulinum toxin, but they can occur as early as 6 hours or as late as 10 days. Those symptoms usually include dry mouth, difficulty swallowing, slurred speech, muscle weakness, double vision, vomiting, and severe diarrhea, along with a progressive muscle paralysis. These are all symptoms of the muscle paralysis caused by the bacterial toxin. If untreated, these symptoms may progress to cause paralysis of the arms, legs, trunk, respiratory muscles, and possibly eventual death. In all cases the toxin made by C. botulinum causes illness, not the bacterium itself.

Infant botulism

Infant botulism is the most common form of the ailment in the United States. The mode of action of this form is through actual infection by germinating spores in the gut of an infant. Infection results in constipation, general weakness, loss of head control and difficulty feeding. Because of these symptoms, infant botulism is often referred to as floppy baby syndrome.

Honey, corn syrup, and other sweeteners are potentially dangerous for infants. This is because the mixture of the non-acidic digestive juices of an infant, the human body temperature, and an anaerobic environment creates an ideal medium for botulinum spores to grow and produce toxin. Botulinum spores are among the few bacteria that survive in honey, but they also are widely present in the environment. While these spores are harmless to adults, because of stomach acidity, an infant's digestive system is not yet developed enough to destroy them, and the spores could potentially cause infant botulism. For this reason, it is advised that neither honey, nor any other sweetener, should be given to children until they are weaned.


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Botulism and preserved green olives
From Emerging Infectious Diseases, 5/1/05 by Amy Cawthorne

To the Editor: In March 2004, a total of 16 suspected cases of botulism were reported to the Italian National Institute of Health by hospitals in 3 adjoining regions in central and southern Italy (Molise, Campania, and Puglia). Initial investigation showed that all patients had eaten at the same restaurant in Molise on February 22 or 24, 2004. The restaurant provided reservation lists for those dates (the restaurant was closed on February 23). It also provided a list of foods that had been served each evening. Persons on the reservation lists were contacted and asked to provide the names of others who had been at their tables to ensure that as many diners as possible were traced. Of 73 persons who had been identified as having eaten at the restaurant on either evening, 66 were successfully contacted and interviewed in person or by telephone about symptoms and food consumed at the restaurant.

For purposes of the investigation, a probable case-patient was defined as a person who had dined at the restaurant on February 22 or 24 and had experienced diplopia or blurred vision and at least 1 of the following symptoms: dysphagia, dry mouth, dysarthria, upper/lower extremity weakness, dyspnea, and severe constipation. Those who met the probable case definition and had laboratory-confirmed botulism were considered definite case-patients.

We tested for botulinum neurotoxin in serum and spores in stool samples as described (1). Serum or stool specimens from 24 patients with [greater than or equal to] 2 symptoms were sent to the Italian National Institute of Health for testing.

Twenty-eight persons reported [greater than or equal to] 2 symptoms (42% attack rate); 25 (89%) were considered probable cases and 3 (11%) were considered confirmed cases. Two members of the restaurant owner's family and 1 employee were among the probable case-patients. Onset of symptoms occurred 4 hours to 6.5 days after eating at the restaurant (median 36 hours). Twenty persons (71%) had been seen in emergency rooms, 15 (53%) were admitted to a hospital, and 18% were admitted to intensive care. None required ventilatory support, and no deaths occurred.

The main symptoms reported by 28 probable and confirmed patients included dry mouth in 25 (89%), dysphagia in 25 (89%), severe constipation in 22 (79%), and blurred vision in 27 (96%). Three weeks alter onset of symptoms, 15 (68%) reporting severe constipation, 11 (41%) reporting blurred vision. 10 (40%) reporting dry mouth, and 11 (44%) reporting dysphagia still had these symptoms. Of the 24 patients for whom rectal swabs were available, 3 were culture-positive for Clostridium botulinum type B. None of 5 serum samples tested positive.

Food-specific attack rates, relative risks (RRs), and 95% confidence intervals (CIs) were calculated. A Poisson model with robust error variance was used to estimate RR with adjustments for possible confounding and effect modification (2). Foods associated with illness with p values <0.20 were considered in the model.

In a univariate analysis in which all 28 patients were considered, the RR of illness was higher among diners who ate home-preserved green olives in salt water (RR 5.2, 95% CI 1.4-19.8), ate cream pastries (RR 2.5, 95% CI 1.8-3.4), and drank homemade lemon liqueur (RR 2.1, 95% CI 1.3-3.4). After multivariate analysis, only the risk associated with eating green olives remained significant (RR 5.2, 95% CI 1.4-19.8).

None of the food items served on February' 22 or 24 was available for sampling, and none of the other 13 food samples obtained from the restaurant was positive for C. botulinum. However, the pH of a jar of olives that had been prepared at the same time as those eaten on February 22 and 24 was 6.2, tar above the level of 4.6 required to prevent growth of C. botulinum. No salinity testing was performed by the local laboratory, and inadequate storage during transit made it impossible to conduct salinity and water activity tests at the national reference laboratory.

Interviews with the restaurant proprietors indicated that the olives were prepared on site during the tall of 2003 from local olives. After soaking in salt water for 35 days, the olives had been decanted into jars, and salt water had been replaced with fresh water. Neither the amount of salt used in the salt water mixture nor the pH at any stage was standardized during preparation.

Both epidemiologic evidence and information obtained regarding preparation of the olives strongly suggest that they were the likely source of the outbreak. This outbreak highlights the previously documented risk associated with improperly prepared olives (3-5). In Italy and elsewhere in Europe, an increasing trend favors traditional foods and preparation methods over large-scale industrial products. This outbreak underlines the importance of providing training and periodic monitoring of those involved in small-scale preparation to ensure that disease risks from improperly prepared or stored foods are minimized.


We thank the staff of the local health unit and Carabinieri force for their logistic support of the field investigation, Primula Semprini for providing laboratory results for food samples. Alain Moren for scientific support and advice, and Nancy Binkin for her assistance in reviewing the manuscript.

* European Programme for Intervention Epidemiology Training, Rome, Italy; and [dagger] Istituto Superiore di Sanita Rome, Italy


(1.) Food and Drug Administration. Bacteriological analytical manual online. January 2001 [cited 2005 Feb 10]. Available from

(2.) Zou G. A modified poisson regression approach to prospective studies with binary data. Am J Epidemiol. 2004;159:702-6.

(3.) Fenicia L, Ferrini AM, Aureli P. Epidemia di botulismo da olive nere. Industrie Alimentari. 1992;31:307-8.

(4.) Padua L, Aprile I, Lo Monaco M, Fenicia L, Anniballi F, Pauri F et al. Neurophysiological assessment in the diagnosis of botulism: usefulness of the single-fiber EMG. Muscle Nerve. 1999;22:1388-92.

(5.) Endoh M. Okuno R, Shimojima Y, Murata I, Sekine H, Kokubo Y. Botulism, Japan. Infectious agents surveillance report. [cited 2005 Feb 10]. 2000; 21:54. Available from

Amy Cawthorne,* Lucia Pastore Celentano,* [dagger] Fortunato D'Ancona, [dagger] Antonino Bella, * Marco Massari, [dagger] Fabrizio Anniballi,* Lucia Fenicia, [dagger] Paolo Aureli, [dagger] and Stefania Salmaso [dagger]

Address for correspondence: Amy Cawthorne, European Programme for Intervention Epidemiology Training, Centro Nazionale di Epidemiologia Sorveglianza e Promozione della Salute, Reparto di Epidemiologia delle Malattie Infettive, Istituto Superiore di Sanita, Viale Regina Elena 299, 00161 Rome, Italy; fax: 39-06-4423-2444; email:

COPYRIGHT 2005 U.S. National Center for Infectious Diseases
COPYRIGHT 2005 Gale Group

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