Reservoirs of Porcine Circoviruses: A Mini Review

Zhai, Shao-Lun; Lu, Shou-Sheng; Wei, Wen-Kang; Lv, Dian-Hong; Wen, Xiao-Hui; Zhai, Qi; Chen, Qin-Ling; Sun, Yan-Wei; Xi, Yun

In 2011, a circovirus-like virus sequence (PorkNW2, GenBank accession number HQ738638) was discovered in both pork and beef samples from stores in San Francisco (18) . In 2014, two similar sequences were re-detected in beef samples from the Sunset district of San Francisco (19) . In fact, these circovirus-like virus sequences were significantly close to the aforementioned PCV3 in pigs (11, 12) . Based on these research reports, it is speculated that PCV3 is also widespread in cattle. A recent epidemiological investigation from China confirmed our speculation. Their results showed that 74 out of 213 (34.7%) clinically healthy bovine samples from eight regions in the Shandong Province were positive for PCV3, and that the bovine-origin PCV3 genome sequences had a close relationship with porcine-origin PCV3 genome sequences (24) . Surprisingly, PCV3 was also reported in the samples of wild chamois and roe deers (25) . The data suggest that ruminants, especially cattle, are noteworthy reservoirs of PCVs. These epidemiological data bring to light two important scientific issues that warrant further research: (1) to determine whether PCV3 has a multihost receptor and (2) to identify whether some cross-species transmission routes (such as direct contact, insect biting) might contribute to the circulation of PCV3 in pigs and ruminants.