Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: June 3, 1999
Publication Date: N/A
Technical Abstract: Transportation of pigs is known to cause varying levels of stress, depending on a number of factors including: crowding, temperature, social status, and duration of trip. On-farm studies to determine the effects of transport stress on Salmonella shedding can be very problematic. Previously, we developed a porcine stress model using a glucose analog, 2- deoxy-D-glucose (2DG) to stimulate physiological stress. Administration o 2DG induces many hallmark signs of stress such as increased blood glucose and cortisol concentrations, and decreased lymphocyte proliferation activity. This model eliminates many confounding variables often associated with transportation stress models. In this study, a Salmonella infection model was combined with the porcine stress model to study the effects of stress on Salmonella shedding. Pigs were inoculated intranasally with 1 x 10**6 S. choleraesuis and allowed to develop the carrier-state. At 6 and 7 wks postinoculation (PI) pigs were stressed wit 2DG and dexamethasone (Dex), respectively. Individual fecal loops were collected and quantitatively cultured for Salmonella on days: 1, 2, 3, 8, 15, 22 PI; 0, 1, 2, 4, 7 post-2DG administration; and 0, 2, 3, 4, 8 post- Dex administration. Results indicate that experimental stress does not necessarily cause recrudescence of Salmonella shedding even when tissues are culture positive for Salmonella. Persistent shedding was not effected by 2DG; however, Dex caused a 20-fold increase in Salmonella shedding. Perhaps a new paradigm is needed to accurately describe the Salmonella carrier-state in swine. Carriers should be divided into two subgroups: (a) carriers unaffected by stress, and (b) persistent-shedders that cycle between the active and inactive carrier-state.