Clostridia are not normally considered to be zoonotic pathogens, although many species affect both humans and domestic animals. Three cases in which organisms occur, possibly via direct or indirect transmission, in both food animals and humans are considered here. Strains of Clostridium perfringens that produce enterotoxin (CPE) are typically transmitted to humans in contaminated, improperly handled foods. Pathogenesis is based upon action of CPE in the intestine, and disease is usually self-limiting. Infection of domestic animals by CPE-producing C. perfringens is uncommon. C. perfringens type C is best known as a pathogen of neonatal domestic animals, which acquire the infection from the dam. The course may be peracute, and prevention by vaccination of the dam is universally advocated. Humans consuming meat contaminated with type C may develop enteritis necroticans, with segmental hemorrhagic and necrotic jejunitis, which must usually be treated by bowel resection. Clostridium difficile is a pathogen of both humans and domestic animals. Examination of retail meats by bacteriologic culture has revealed genotypes of C. difficile that in many cases are identical to those from food animals and diseased humans. Transmission, food animals to foods to humans, has not been documented.

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