41: Botulism

HISTORY AND EPIDEMIOLOGY

Botulism, a potentially fatal neuroparalytic illness, results from exposure to botulinum neurotoxin (BoNT), which is produced by the bacterium ­Clostridium botulinum and other Clostridium species. The earliest cases of botulism were described in Europe in 1735 and were attributed to improperly preserved German sausage; the name of the disease alludes to this association, botulus being Latin for sausage. Emile van Ermengem identified the causative organism in 1897 and named it Bacillus botulinum; it was later renamed Clostridium botulinum.²² These Gram-positive, spore-forming bacteria produce seven serotypes of BoNT, denoted A through G.

In adults, most cases are due to contaminated food, resulting from ingestion of toxin, whereas in infants most cases result from ingestion of bacterial spores which proliferate and produce toxin in the gastrointestinal (GI) tract. Less common forms of botulism include wound botulism, in which spores are inoculated into a wound and locally produce toxin, and inhalational botulism due to aerosolized BoNT, potentially used as a weapon of bioterrorism.

Botulism outbreaks can occur anywhere in the world¹¹⁵ and have been reported from such diverse areas as Iran,¹⁰³ Japan,⁹⁷ Thailand,⁷⁰ France,¹­Portugal,⁷⁴ and Canada.⁹¹ In 2011, a total of 140 cases of botulism were reported to the US Centers for Disease Control and Prevention (CDC). Food-borne botulism constituted 14% of cases, infant botulism 73% of cases, and wound botulism 9%.³⁸ In this analysis, toxin type A accounted for the majority of cases of food-borne botulism (70%) and all cases of wound botulism, and infant botulism was due to toxin type A in 40% and to toxin type B in 59% of cases.³⁸ No deaths from food-borne botulism were reported in 2011. The case fatality rate has improved for all botulism toxin types, probably due to increasing awareness of the condition and consequent earlier diagnosis, appropriate and early use of antitoxin, and better and more accessible life support techniques.

In the past 50 years, home-processed food has accounted for 65% of outbreaks, with commercial food processing constituting only 7% of reported cases; in the remaining outbreaks, the origin is unknown.³⁴ Common home-canning errors responsible for botulism include failure to use a pressure cooker and allowing food to putrefy at room temperature. Minimally processed foods such as soft cheeses may lack sufficient quantities of intrinsic barriers to BoNT production, such as salt and acidifying agents.¹⁰⁹ These foods become high-risk sources of botulism when refrigeration standards are violated. The US Food and Drug Administration (FDA) continuously reviews recommendations for appropriate measures to process such foods.^137,138

Awareness of evolving trends and unusual presentations or locations of botulism permits the establishment of preventive education programs. Outbreaks of botulism have been associated with specialty foods consumed by different ethnic groups, such as chopped garlic in soy oil by Chinese in Vancouver, British Columbia^91,...