Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease, caused by PRRS virus (PRRSV), that critically affects the swine industry. While the detection of PRRSV genes plays a key role in PRRS control, the PRRSV genome is known to undergo frequent mutation. Nevertheless, primer pairs widely used for the detection of PRRSV genes were designed between 1995 and 2010. The reliability of these primer pairs for the detection of currently circulating PRRSVs is therefore questionable. Here, we investigated the sensitivity of the previously reported primer pairs to detect PRRSV genes that have been recently isolated or detected in Japan. In addition, based on nucleotide sequences from the recent Japanese PRRSVs, we designed four new primer pairs for the detection of PRRSV genes. The sensitivity and specificity of the new primer pairs were evaluated by quantitative reverse transcription PCR using RNA extracted from PRRSV isolates, swine serum, and oral fluid specimens collected from PRRS-affected pigs, and swine sera collected from a PRRSV-free pig farm in Japan. One of novel primer pairs used in our study exhibited greater sensitivity than the previously reported primer pairs, and is thus more reliable for the detection of PRRSV genes.
