Genetic Characterization of Porcine Circovirus Type 2 Detected from the Pigs in Commercial Swine Farms in Korea

Porcine circovirus type 2 (PCV-2) has been nowadays recognized as a major agent causing postweaning multisystemic wasting syndrome (PMWS) in pigs worldwide. PMWS most commonly affects the weaned piglets, being of increasing importance to the pig industry in Korea. Seven commercial farms affected with PMWS and 2 farms free from PMWS, located in the southern part of Gyeonggi province, were selected for this study. The peripheral mononuclear cells were tested for the presence of ORF2 gene by PCR, and 54 (68.4%) of 79 samples were positive. All of 9 herds tested included the positive cases. The positive rates by herds were 50 to 100% in the PMWS-affected herds and 40 to 62.5% in the PMWS-free herd. The nucleotide and amino acid sequences of ORF2 gene of 6 strains were characterized. Homologies among 6 strains revealed 92.1 to 100% in the nucleotide and 92.3 to 100% in the amino acid. The overall ranges of homologies for 25 strains comprised 2 Korean and 23 foreign strains were 91.1 to 100% in the nucleotide and 89.7 to 100% in the amino acid. Three regions of greater heterogeneity were found in immunorelevant epitopes of the capsid protein, and the sequences between 57 to 80 aa revealed higher mutation than other areas. In the phylogenetic tree analysis, KOR 71 strain was clustered together with Korean strains previously isolated in Korea. The remaining 5 strains were closely clustered with other European and Asian strains. The results will be valuable for improving our understanding of the molecular epidemiology of PCV-2 in Korea and development of preventive measures for PMWS.