Botulism is a life-threatening paralytic illness caused by neurotoxins produced by an anaerobic, gram-positive, spore-forming bacterium—Clostridium botulinum. Botulism is a rare disease and only affects a few hundred persons each year in the United States. The vast majority of clinicians have never seen a patient with botulism.
There are four generally recognized naturally occurring types of botulism: foodborne, wound, infant, and, rarely, adult intestinal colonization. Iatrogenic (from a medical injection) and inhalational botulism may also occur.
Foodborne botulism: Foodborne botulism is the type that is classically associated with clinical botulism. Foodborne botulism is caused by eating foods that contain botulinum toxin. In foodborne botulism, it is the pre-formed toxin that causes illness, not the bacterium itself. The incidence of foodborne botulism is extremely low, usually fewer than 25 cases per year in the United States. Nonetheless, the extreme danger posed by the toxin has required that “intensive surveillance is maintained for botulism cases in the United States and every case is treated as a public health emergency.” This danger includes a mortality rate of up to 65% when victims are not treated immediately and properly. Treatment consists of supportive care (including mechanical ventilation if required), and an antitoxin may be given (upon approval from health authorities) that can bind free toxin and delay progression if used early in the course of illness. Most of the foodborne botulism events reported annually in the United States are associated with home-canned foods that have not been safely processed. Occasionally, though, commercially processed foods are implicated as the source of a botulism event, including sausages, beef stew, canned vegetables, and seafood products.
Wound botulism: Wound botulism occurs when a wound becomes infected with Clostridium botulinum spores that then begin to produce toxin. The toxin gets absorbed into the bloodstream and leads to symptoms of botulism poisoning. Wound botulism often occurs in the setting of an infected injection site where contaminated heroin has been used, but occasionally, it can occur with other wounds as well. There are generally fewer than 20 cases of wound botulism per year in the United States.
Infant botulism: Infant botulism is the most common form of botulism in the United States, with approximately 150 cases per year. In infant botulism, the Clostridium botulinum bacteria grow in the intestines of the infant (because of less competition from the “normal” gut bacteria that adults carry) and begin to make toxin. Infant botulism has a good prognosis when detected and treated. Treatment is with an antitoxin called botulism immune globulin intravenous (BIGIV).
Intestinal colonization: This is a very rare kind of botulism that can occur if bacterial spores get into an adult’s intestines and produce toxin (similar to infant botulism). This only occurs in individuals with disrupted intestinal bacterial flora because of specific medical conditions.