1a.Objectives (from AD-416):
Develop a precise and accurate estimation of duration of infection within the lymph nodes of cattle for various serotypes and subpopulations of Salmonella, an understanding of cellular tropism across various serotypes with and without interventions, and a rapid and well-controlled evaluation of candidate interventions designed to reduce the duration of infection within lymph nodes of cattle (particularly targeted to those subpopulations of Salmonella identified above).
1b.Approach (from AD-416):
A multi-pronged inoculator (e.g., 10-lancet) allergy skin-testing device is inoculated with a Salmonella broth and applied with mild pressure to specific regions of the bovine's hide that are drained to region-specific lymph nodes. Different subtypes or serotypes of Salmonella can be applied to different regions of the animal. This process may be repeated at the time of initial inoculation or at subsequent days. At various time points after inoculation, the calves are sacrificed and the lymph nodes recovered and Salmonella presence can be determined or quantified using various methods. Various statistical approaches (such as survival analysis) can be performed to estimate duration of infection. Moreover, candidate interventions can be applied to a portion of the calves to evaluate any impact on the duration of infection within peripheral lymph nodes.
This is a new project, with the goal of evaluating potential interventions (e.g., vaccines) for prevention of Salmonella uptake by, or to enhance Salmonella elimination from infected peripheral lymph nodes in, cattle. Work in FY 2013 focused on protocol development and implementation of initial studies which demonstrated some success in the use of vaccines to prevent Salmonella uptake by the lymph nodes. Subsequent research by this project will assess new experimental vaccines as well as other potential interventions. As work under this project progresses, important new information will be generated that will not only yield insight on how to control this important food safety pathogen, but will also increase our understanding of Salmonella uptake and elimination from the lymph nodes of cattle.