Abstract
The emergence in Japan of field isolates of type 1 porcine reproductive and respiratory syndrome virus (PRRSV) suggests problems with control. We therefore developed a one-step real-time reverse transcription polymerase chain reaction (qRT-PCR) with improved sensitivity that detects as little as 1 × 10(-2) TCID50/ml of viral RNA. We tested serum samples collected in January and September 2008, October 2009 and January 2011 from a farm with an outbreak and found infected pigs between January and September 2008, but not in January 2011. Further, between 2008 and 2011, we did not detect infection in pigs at 8 nearby farms or in 2,052 serum samples collected from pigs from 74 farms in 12 prefectures. This assay should help prevent future outbreaks.