Salmonellas are common commensals of all animals and birds and are excreted in feces. The main reservoirs for human infection are poultry, cattle, sheep and pigs. Infection in animals is maintained by recycling slaughterhouse waste as animal feed, fecal oral spread and fecal contamination of hatching eggs. Transmission occurs when organisms, introduced into the kitchen in poultry carcasses, meat or unpasteurized milk, multiply in food owing to inadequate cooking, cross-contamination of cooked foods and inadequate storage. The organism inhabits the intestinal tract of many animals including birds, cattle, sheep, pigs, lab.
Salmonella occurs worldwide.
The house mouse may also be a reservoir of the infection and may play a role in human and animal salmonellosis. Humans, rarely, and animals may be carriers and asymptomatic shedders of the organism. In the laboratory and teaching laboratory, birds, reptiles, and turtles are especially dangerous sources of Salmonellosis. Turtles alone in 1970 may have caused 280,000 human cases of Salmonellosis. Indirect transmission via contaminated food and water are the most common sources but transmission may also be by direct contact.