Do porcine parvoviruses 1 through 7 (PPV1-PPV7) have an impact on porcine circovirus type 2 (PCV2) viremia in pigs?

Infections with porcine parvoviruses 1 through 7 (PPV1-PPV7) and porcine circovirus type 2 (PCV2) are widespread in pig population. PCV2 is involved in a number of disease syndromes collectively called PCV2-associated diseases (PCVD). It is well elucidated, that PPV1 may act as a triggering factor of PCVD through supporting PCV2 replication. Less is known about the PPV2-PPV7 impact on PCV2 viremia, but several authors suggested an association between these viruses. In order to provide a better understanding of PCV2 and PPVs co-infections, 519 serum samples from eight Polish swine farms were tested by real-time PCR to assess the possible impact of PPV1-PPV7 on PCV2 viremia. Among all 519 serum samples, 30.6 % were positive for PCV2 and PPVs detection rates ranged from 2.9 % (PPV1) to 26.6 % (PPV2). Within 159 serum samples categorized as PCV2-positive, the prevalence rates of PPVs ranged from 7.5 % (PPV1) to 37.1 % (PPV6). The level of PCV2 viremia was significantly higher only in serum samples positive for PPV1 and PPV7 compared to samples negative for these PPVs. Moreover, the correlation between Ct values for PPV7 and PCV2 was observed. Thus, our results suggested that apart from PPV1, also PPV7 stimulate the replication of PCV2.