Early Detection of Porcine Reproductive and Respiratory Syndrome Virus Outbreak: Combination of Methods

The current application of the production data exponentially weighted moving average (EWMA) model can detect PRRSV outbreaks earlier than that of processing fluid (PF) testing; however, its advantages have not been fully reported. This study aimed to analyze various production parameters, including abortion, off-feed, low appetite, and dead sows, on a daily basis following a PRRSV outbreak in an II-vx sow farm. The EWMA method was employed and the results were compared with the early detection of positive PF results. Differences in daily abnormal indicators across the three PRRSV status periods were analyzed. Additionally, this study evaluated the PRRSV detection rates in different sample types (AF, OS, and TBS) from aborted sows and compared the detection rates of different sample combinations using statistical tests. The 187-day study revealed that the first true positive (TP) alarm point for daily abortion sows occurred on day 107 and for off-feed sows on day 110. In contrast, the first RT-qPCR-positive result for PF was obtained on Day 122. The average values of daily abortions and off-feed sows in status I-A were significantly higher than those in status II-vx and I-B. Conversely, the average value of low appetite in status I-A was significantly lower than that in statuses II-vx and I-B. No significant differences were observed in the daily number of dead sows among the three groups. The RT-PCR detection rates varied significantly (p < 0.01) among the different sample types (AF, 43.04%; TBS, 65.82%; and OS, 74.68%), with amniotic fluid (AF) showing the lowest detection rate. Combining AF and oropharyngeal swabs (OS) samples yielded a higher detection rate than combining AF and TBS samples. Using the EWMA to monitor the daily number of aborted sows was effective for the early detection of PRRSV outbreaks.