Most research that has been done on studying Salmonella infections at the farm level has focused on the animal to animal transmission of the organism. Fecal-oral transmission has been well documented, and is the primary means for dissemination of Salmonella within a population. However, investigation into identifying the specific sources for the introduction of Salmonella into a population and its perpetuation on swine farms have not been completed in detail. Information on the dynamic nature of the Salmonella infection-contamination-infection cycle (the horizontal exchange of Salmonella between the animals and their corresponding environment) in swine production is a prerequisite for effective control measures of Salmonella at the farm level.