Retrospective survey and phylogenetic analysis of porcine circovirus type 3 in Jiangsu province, China, 2008 to 2017.

Porcine circovirus type 3 (PCV3) is a novel porcine circovirus recently identified in pigs associated with porcine dermatitis nephropathy syndrome, reproductive failure and multi-systemic inflammation. This study aimed to identify PCV3 in clinical samples from pigs collected between 2008 and 2017 in Jiangsu province, China. A total of 272 pig tissue samples from 141 pig farms in Jiangsu province were examined and analyzed. Forty of the 272 (14.7%) samples tested were positive for PCV3, while 28/40 (70%) of the PCV3-positive samples were co-infected with PCV2. Among them, 18, 1, 14 and 7 of the PCV3-positive samples were identified in 2013, 2014, 2015 and 2017, respectively. The complete genome sequences from four of the PCV3s contained 2,000 nucleotides, and shared 98.6% to 99.6% nucleotide sequence identity with the PCV3 isolates available in GenBank. Our results indicate that a large outbreak of PCV3 occurred in Jiangsu province pig herds in 2013, after which a fairly stable infection rate was recorded. It is imperative, therefore, to gain a better understanding of the pathogenicity of PCV3 and control its further dissemination in this region.