Identification of an emerging recombinant cluster in porcine circovirus type 2.

Porcine circovirus type 2 (PCV2) is continuously evolving through point mutation and genome recombination. In the present study, genetic affiliations of 40 PCV2 strains were determined by amplification, sequencing and phylogenetic analyses during the nationwide molecular epidemiology investigation from 2009 to 2010 in mainland China. The results revealed that PCV2b was the predominant genotype in mainland China from 2009 to 2010 and PCV2b-1C within PCV-2b genotype was an emerging predominant subtype. More interestingly, five strains (09HaiN-1, 09HaiN-2, 10AH, 10GX and 10QH) were classified into a novel cluster along with the two main PCV2 genotypes PCV2a and PCV2b. Further analyses revealed that this novel cluster arose from recombination between PCV2a and PCV2b stains within the ORF2 gene. Moreover, BLAST search on NCBI website revealed that PCV2 strains of the novel cluster also emerged in Thailand, Indonesia and Laos, indicating that the novel cluster of PCV2 has also been circulating in some other Asian countries. This study is the first time to perform comprehensive analyses to demonstrate a cluster of PCV2 strains derived from the same type of inter-genotypic recombination pattern. Our findings provide valuable information on PCV2 evolution.