Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2009
Publication Date: July 12, 2009
Citation: Rostagno, M.H., Eicher, S.D., Lay Jr, D.C. 2009. Salmonella infection and immune response in finishing pigs. American Society of Animal Science. ASAS Proceedings CD. Technical Abstract: Finishing pigs infected with Salmonella pose significant food safety risks by carrying the pathogen into abattoirs. A study was conducted to determine the dynamic of Salmonella infection in finishing pigs, and the immunological alterations that occur in Salmonella-carrier pigs, by longitudinally comparing infected pigs that carry and shed Salmonella to non-infected pigs. Pigs (n=24) were individually inoculated with Salmonella Typhimurum. Fecal and blood samples were collected from each pig, and 3 pigs were randomly selected and euthanized to collect additional samples (spleen, liver, mesenteric lymph node, ileum, and cecum) on days 1, 2, 7, 14, 21, 28, 35, and 42 post-inoculation (p.i.). A control group (n=15) of non-infected pigs was maintained for comparison by sampling at 1, 2, 7, 14, and 21 days. No inoculated animal showed any clinical sign of infection. Bacteriological data revealed that all inoculated pigs started shedding Salmonella within 24 h p.i., and persistently shed the bacteria up to the end of the study. Ileal and cecal content samples were all positive throughout the study. Mesenteric lymph nodes were also positive during the entire study and at the same level as intestinal content samples. All samples contained 3-4 logs (cfu/g) of Salmonella at 24 h p.i., and 4-5 logs (cfu/g) of Salmonella up to 4 wk p.i. Interestingly, levels of Salmonella dropped markedly in all samples at 5 wk p.i., being detectable only by enrichment. The number of peripheral blood monocytes tended to be less in infected pigs, with no difference between groups for other white blood cell measures. Tumor necrosis factor-a was greater in infected pigs: 1) in the mesenteric lymph nodes by 48 h p.i.; 2) at 24 h and 3 wk p.i. in the ileum; and 3) in the cecum and spleen by 3 wk p.i. Interleukin-12, IL-1 and its antagonist, and a porcine specific antimicrobial peptide RNA expression in tissues changed over time, but were not different between groups. Immune data demonstrate that site specific immune changes occurred first, followed by more peripheral responses. These results will enable us to develop and plan the application of potential intervention strategies that will contribute to increase pork safety.