Long-term survival and infectivity of Salmonella choleraesuis

It is believed that Salmonella Choleraesuis, the host-adapted serotype of swine, does not survive well outside the host. We examined the survival capability as well as the presence of latent DNA of S. Choleraesuis in swine feces. Pigs were infected with S. Choleraesuis and feces was collected and pooled on days 2, 4, 7, and 10 post inoculation (PI). Feces was 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, S. Choleraesuis was recovered from at least 13 months. Direct PCR analysis did not detect S. Choleraesuis subsequent to the final culture recovery for any stored sample. We also examined the infectivity of S. 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, S. Choleraesuis was widely disseminated among the tissues of all the pigs inoculated. This study demonstrates that S. Choleraesuis remains viable and infective in the environment. Therefore, contaminated fecal matter can serve as a reservoir for S. Choleraesuis as well as other Salmonella spp. Control measures must consider this environmental reservoir as a source of new infections.