Use of a dRT-PCR assay to efficiently detect HP-PRRSV in crude serum samples. (A) Amplification plots for dRT-PCR and cRT-PCR assays. Threshold was set at 0.01. (B) Amplicons from the dRT-PCR assays and controls were electrophoresed on 3.5% (w/v) agarose gels. The arrows indicate the 73-bp target bands for HP-PRRSV. A 1 μL of purified HP-PRRSV RNA (Lane 1), 1 μL of HP-PRRSV-containing serum (Lane 2) and 1 μL of PRRSV-negative serum (Lane 3) were added to a 25 μL dRT-PCR mixture, respectively. All assays were performed in triplicate.