The objectives of this research were to explore the use of swine oral fluids, a type of aggregate sample, in infectious disease surveillance. In Chapter 2, the uses and surveillance applications of aggregate samples are reviewed. As reported in the refereed literature, bulk tank milk samples from ovine, bovine, and caprine herds have been tested to determine disease status and herd immunity. Likewise, swine producers and veterinarians have used oral fluid testing for disease detection and the evaluation of herd immunity. In Chapter 3, sampling guidelines for oral fluid surveillance in commercial swine herds are presented. These guidelines are the result of field-based research in which oral fluids were collected weekly from 3 barns on one wean-to-finish farm for 9 weeks and tested for porcine reproductive and respiratory syndrome virus (PRRSV) RNA. Results were modeled using a piecewise exponential survival model to provide estimates of the probability of detection by disease prevalence, sample size, and diagnostic assay performance. Notably, this study showed that fixed spatial sampling was as good, if not better, than simple random sampling and that probability of detection on a swine farm improved significantly when multiple barns on the farm were sampled. In Chapter 4, a combined IgM-IgA PRRSV oral fluid ELISA was evaluated for its ability to detect pig-derived antibody produced in response to infection in the presence of maternal antibody. Two studies were performed. In Study 1 (experimental conditions), oral fluid samples were collected daily from 12 PRRSV-negative pigs from days post vaccination (DPV) -7 to DPV 42. Pigs were vaccinated using a modified-live PRRS vaccine on DPV 0. In Study 2 (field conditions), oral fluids were collected weekly from 3 wean-to-finish sites, each with 3 barns, for a total of 9 samplings. Testing of oral fluids from both studies by IgG, IgM, IgA, and IgM-IgA ELISAs showed that the IgM-IgA ELISA was able to detect pig-derived IgM and IgA in the face of circulating maternal antibody and that the combined IgM-IgA assay provided better performance than detection of either IgM or IgA alone.</p
