Oral fluid samples used for PRRS diagnosis and management

Porcine reproductive and respiratory syndrome (PRRS) is an economically significant swine disease having a negative impact to the swine industry worldwide. Appropriate management strategies and diagnostic tests are crucial to successfully control PRRS virus (PRRSV). However, the application for oral fluid-based diagnosis has not been evaluated in the Thai farms previously. In this study, pre-extraction methods of oral fluids were evaluated to improve the PCR product yielded. Moreover, the oral fluids utilization for PRRSV monitoring during the gilt acclimatization and farrowing to nursery period was investigated. The results demonstrated that increasing sample volume might be a suitable simple method for column-based extraction kit to improve PRRSV detection. Whereas, other modified pre-extractions could possibly impact nucleic acid quality in the samples. In addition, field evaluation demonstrated that oral fluid testing provided convenient, economical, satisfied and animal welfare friendly method of sample collection with some limitations. Significant positive correlation was found between oral fluid results and the results from serum samples. Mean S/P ratios of oral fluid samples showed significantly higher levels than those of from the serum samples with similar patterns. During acclimatization period, oral fluid testing could be used to monitor the success of acclimatization. However, it did not completely monitor all PRRSV infection in acute phase of infection. In the farrowing to nursery study, oral fluid testing provided satisfied performance to determine PRRS status especially when having moderate to high prevalence. The changes in anti-PRRSV antibodies status in oral fluids after horizontal exposure were concurrently with the presence of high viral loads. In conclusion, oral fluid testing is a suitable sample for PRRSV monitoring. Additionally, the baseline and application for oral fluid-based diagnosis are of essential to explore on its utilization. The finding data would beneficial to the farmers and the future utilization for successful PRRS prevention and control.