| Porcine reproductive and respiratory syndrome (PRRS) is a viral disease of swine that has an important economic impact on the swine industry. Herds that are free of PRRS virus (PRRSV) are at high risk of infection, consequently, their PRRSV status needs to be monitored regularly to identify new infections. The general objective of this dissertation was to gain new information that can be used to improve PRRSV surveillance in farms negative for PRRSV.;Surveillance in negative sow farms is generally done by testing for PRRSV antibodies in serum of sows by enzyme-linked immunosorbent assay (ELISA). The accuracy of this procedure, in terms of its sensitivity and specificity, is limited. Therefore, the use of pooled sample testing was evaluated as a strategy to improve these surveillance protocols. It was shown that the conventional monitoring protocols based on ELISA on individual samples could be improved by using pooled-sample testing.;Surveillance protocols currently used in boar studs are generally based on the reverse trascriptase polymerase chain reaction test; however, protocols differ in sample size, sampling frequency and sample specimen used. The performance of these different monitoring protocols was evaluated using a simulation model. Results from the model suggested that an intensive monitoring protocol is needed in order to detect a PRRSV introduction in a boar stud within the first days. Because of the high cost associated with frequent blood sampling of a large number of boars, the feasibility of using pooled sample testing was investigated using an experimental infection study. Results indicated that pooled sample testing decreased the sensitivity of the surveillance protocols. This decrease in sensitivity should be considered when designing surveillance protocols.;Surveillance protocols based on on-site testing could lower testing costs and turnaround time. The feasibility of using a diagnostic test based on recently developed technology called loop mediated isothermal amplification to detect PRRSV was explored in the laboratory. Validation experiments indicated that it was possible to specifically detect PRRSV in just one hour with a simple and inexpensive heat block. |
