Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/10/2001
Publication Date: 7/20/2001
Citation: Gray, J.T., Cray, P.J. 2001. Survival and infectivity of salmonella choleraesuis in swine feces. Journal of Food Protection. 64: (7) P. 945-949. Interpretive Summary: Salmonella choleraesuis preferentially infects swine and can cause increased morbidity and mortality resulting in millions of dollars of lost income for the swine industry. Because of the preferential colonization, many people do not regard S. choleraesuis as an environmental pathogen capable of surviving in the production environment, especially after drying. We infected pigs with S. choleraesuis and harvested their feces which contained S. choleraesuis over several days. We then either air dried the feces or kept it wet. The feces was cultured and numbers of S. choleraesuis were counted. We determined that S. choleraesuis can survive in both a wet and dry state although increased survival was noted after drying. Increased survival in feces collected and dried days after infection was noted. Dried feces was also used to infect pigs and illness was noted although it was less severe than typically observed. These data indicate that S. choleraesuis can survive well in a dried state. Therefore, any organic matter that has not been cleaned from the production environment has the potential to harbor S. choleraesuis and cause infection in pigs.
Technical 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 S. choleraesuis in swine feces. Six 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 for 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 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 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 infection.