Molecular Epidemiology And Evolution Analysis Of Genes Of Porcine Circovirus Type 2 And Porcine Reproductive And Respiratory Syndrome Virus

Porcine circovirus type 2(PCV2) is considered as an important pathogen related to multifactorial disease syndromes in pigs, which has a worldwide distribution and causes huge economic losses for the swine industry. Porcine reproductive and respiratory syndrome virus(PRRSV) is an economically important swine pathogen affecting swine industry worldwide, which is characteristic with genetically extensive variation. Thus, PCV2 and PRRSV are two important pathogens affecting swine industry. Now, co-infection of PCV2 and PRRSV is a common problem in pig farms and co-infected pigs were characterized with severe respiratory symptoms, abortion and extremely weakness, and gradually developed into second disease caused by pathogen of virus or bacteria, which leads to huge economic losses. Thus, epidemiology investigation of co-infection of PCV2 and PRRSV and phylogenetic analysis of PCV2 and PRRSV have reference values for prevention and control of viral diseases in pig populations.To investigate the circulating and co-infection of PCV2 and PRRSV in pig population of China, 192 samples were collected from 6 provinces of Jilin, Liaoning, Heilongjiang, Shanxi, Shandong, Guangdong in China from 2013 to 2015 and the positive rates of PCV2 and PRRSV were 64.3% and 23.4% respectively, while the co-infection rate was 18.5%. The co-infection of two viruses is becoming the main swine diseases in the regions. The main purpose of the paper is to investigate and analysis the infection of PCV2 and PRRSV in the regions, which is important in preventing and controlling the diseases.Phylogenetic analysis of PCV2 indicated that 12 sequenced whole genome sequences of PCV2 belonged to PCV2 d and PCV2 b genotypes. Sequences of SX-Z1, SX-Z3, YQ, JL, SY-M-X3, SY-L-3, SY-L-X6 and SP-2 formed a monophyletic group located between PCV2d-1 and PCV2d-2, while 3 sequences of SY-Z-4, ZD-1 and ZD-7 shared high homology with strain of PCV2 c genotype that was only detected in Denmark before the study. More important, The 3 sequences revealed to be recombinants of strains of PCV2 c and PCV2 b genotypes. The phylogeographic analysis on these sequences suggests that the isolates might be initiated in Denmark and then transmitted into China.Phylogenetic analysis of PRRSV were carried out to understanding the circulating of PRRSV in pig populations of China. Total 12 ORF5, 12 ORF7 and 10 highly variable region of Nsp2 genes were sequenced, and phylogenetic trees based on the ORF5, ORF7 and Nsp2 genes indicated that strains of the North American type were categorized into two groups and five subgroups. A novel deletion of three continuous amino acids of Nsp2 was detected. In addition, a sequence of SDly-2014-1 shared high identity with NADC30 strain of ORF7 gene. In the study, two strains were isolated from positive samples and named as LNsy-2014-1 and HLJyq-2015-1, which were North American type and shared high identities with classic strains of JXA1 and VR2332, respectively. The data contribute to understanding molecular variation and genetic evolution of PRRSV in China.