Survival and infectivity of Salmonella Choleraesuis in swine feces

Abstract

Many serotypes of Salmonella survive well in the environment. Conversely, it is believed that Salmonella Choleraesuis, the host-adapted serotype of swine, does not survive well outside the host. We examined the survival capability of Salmonella Choleraesuis in swine feces. Six pigs were infected with Salmonella Choleraesuis and feces were collected and pooled on days 2, 4, 7, and 10 postinoculation (PI). Feces were stored in a wet and a dry form, and survival was measured over 13 months. Salmonella Choleraesuis was recovered from wet feces through 3 months of storage. In a desiccated (dry) form, Salmonella Choleraesuis was recovered from at least 13 months. Salmonella Choleraesuis shed from swine prior to 4 days PI did not survive as well as that shed 4 days PI or later. We also examined the infectivity of Salmonella Choleraesuis resident in dry feces. Six- or 13-week-old pigs were inoculated with dry feces that had been stored either 2 months or 4 months, respectively. Pigs were inoculated either intranasally or by mixing dry feces with the swine ration. Although clinical signs were mild, Salmonella Choleraesuis was widely disseminated among the tissues of all the pigs inoculated. This study demonstrates that Salmonella Choleraesuis remains viable and infective in the environment. Therefore, contaminated fecal matter can serve as a reservoir for Salmonella Choleraesuis as well as other Salmonella spp. Control measures must consider this environmental reservoir as a source of new infections.