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The goal of the proposed research is to identify critical control points for interventions to reduce Salmonella infection in modem swine production facilities. Intensive ecological sampling will be conducted in long term studies of 8 large, multi-site, modem swine production facilities.
Each farm will be visited monthly for 14 months. At each visit, samples will be obtained from various suspected biological and environmental reservoirs of Salmonella. This includes fecal samples from a cross-section of age classes of swine and from rodents, birds, and medium-sized manmmals, as well assamples of insects, feed, water, and pen floor contents. These samples will be cultured for Salmonella. The Salmonella isolates will be characterized genetically, using modem molecular biological techniques. Using information on genetic similarity and proximity in location and time of sampling, inferences will be made regarding probable modes of transmission of Salmonella to swine. It will be possible to identify likely targets for intervention if (a) particular biological and environmental sources of Salmonella are consistently linked (genetically, temporally, and spatially) to swine, (b) during times of low prevalence, Salmonella is maintained primarily in one reservoir, or (c) new genotypes entering the farm are consistently identified first in a specific reservoir. This project is relevant to the sustainability of US agriculture in that it addresses the NRI program objectives of identifying sources of pathogenic organisms in the environment and understanding their ecology, and is designed to promote development of strategies to eradicate disease-causing microorganisms.