Development of a drtqPCR Assay for Differentiation of PCV-2a and 2b in Shanghai Area

A dual real-time quantitative polymerase chain reaction assay (drtqPCR) was established to detect and differentiate between Porcine circovirus-2a (PCV-2a) and Porcine circovirus-2b (PCV-2b). Genotype-specific primer sets and probes were designed by using sequence data published for different PCV-2 strains. Specificity and sensitivity of the drtqPCR were examined by using PCV-2 isolates with known genotype. Among 367 tissue samples, 44.69% (164/367) were PCV-2 positive. From 164 PCV-2 positive samples, 10.98% (18/164), 92.56% (137/164), and 3.31% (9/164) were positive for PCV-2a, PCV-2b, and both genotypes, respectively. These results suggest that the dif- ferential drtqPCR can be used to detect PCV-2 and to differentiate the 2 genotypes from field sam- ples. The PCV-2 infection is quite common in swine of Shanghai area. Furthermore, the PCV-2b in- fective ratio is far higher than PCV-2a, and PCV-2a/2b mixed infections are also observed but at a lower prevalence in Shanghai area.