@article{funk_davies_nichols_2001, title={Longitudinal study of Salmonella enterica in growing pigs reared in multiple-site swine production systems}, volume={83}, ISSN={["1873-2542"]}, DOI={10.1016/S0378-1135(01)00404-7}, abstractNote={Intensive longitudinal investigations of breeding and growing pig populations in two multiple-site swine production systems were conducted in NC, USA. Five cohorts of sows and individually identified growing pigs from their litters were serially sampled in order to determine the prevalence and serotypes of Salmonella enterica in each stage of production based on fecal culture. In addition to fecal samples, feed and environmental samples were obtained. Fifteen different serotypes were isolated from the two systems, the most frequently isolated serotypes were S. typhimurium var Mbandaka and S. typhimurium var Copenhagen. Pig prevalence estimates ranged from 0 to 48.1%. Environmental contamination was frequently encountered despite cleaning and disinfection. Feed was rarely (2/800, 0.25%) identified as S. enterica positive. We observed highly variable patterns of S. enterica prevalence and serotype profiles within cohorts over time and among cohorts within systems. These observations indicate that point estimates of S. enterica prevalence and serotypes cannot be considered as reliable indicators of the S. enterica status of farms, and that uncontrolled studies of interventions to control S. enterica may yield misleading results. These findings are critical to the design of epidemiological studies of S. enterica on swine farms and may suggest that cohort level, as opposed to farm or company level events or management practices, may be important as potential risk factors for S. enterica fecal shedding in market age pigs.}, number={1}, journal={VETERINARY MICROBIOLOGY}, author={Funk, JA and Davies, PR and Nichols, MA}, year={2001}, month={Oct}, pages={45–60} }
 @article{funk_davies_morrow_nichols_2000, title={Temporal patterns of Salmonella enterica prevalence and serotypes in breeding and growing swine populations}, journal={Proceedings of the 9th symposium of the International Society for Veterinary Epidemiology and Economics, Breckenridge, Colorado, USA, August 6-11 2000}, publisher={International Society for Veterinary Epidemiology and Economics (ISVEE)}, author={Funk, J. A. and Davies, P. R. and Morrow, W. E. M. and Nichols, M. A.}, year={2000}, pages={203} }
 @article{funk_davies_nichols_2000, title={The effect of fecal sample weight on detection of Salmonella enterica in swine feces}, volume={12}, ISSN={["1943-4936"]}, DOI={10.1177/104063870001200504}, abstractNote={The effect of different fecal sample weights on the detection of Salmonella enterica in swine feces was examined. Sample weights evaluated were rectal swabs and fecal samples weighing 1 g, 10 g, and 25 g. Comparisons were made on matched fecal samples obtained from individual pigs housed on 2 commercial swine farms in North Carolina. Relative sensitivity (number of positive pigs per fecal weight category/number positive in all weight categories) increased ( P < 0.001) with fecal sample weight, and ranged from 9% for rectal swabs to 78% for 25-g samples. Stomaching of fecal samples did not affect detection of S. enterica. These observations demonstrate that fecal sample weight can markedly influence estimates of prevalence of S. enterica in epidemiologic studies. Failure to consider the imperfect sensitivity of bacterial culture in the design and interpretation of epidemiologic studies will lead to underestimation of prevalence and reduced power to detect the presence of S. enterica-infected herds.}, number={5}, journal={JOURNAL OF VETERINARY DIAGNOSTIC INVESTIGATION}, author={Funk, JA and Davies, PR and Nichols, MA}, year={2000}, month={Sep}, pages={412–418} }