Global molecular genetic analysis of porcine circovirus type 2 (PCV2) sequences confirms the presence of four main PCV2 genotypes and reveals a rapid increase of PCV2d

Chao-Ting Xiao, Patrick G Halbur, Tanja Opriessnig

Research output: Contribution to journalArticlepeer-review

Abstract

The oldest porcine circovirus type 2 (PCV2) sequence dates back to 1962 and is among several hundreds of publically available PCV2 sequences. Despite this resource, limited studies have investigated the global genetic diversity of PCV2. To evaluate the phylogenetic relationship of PCV2 strains, 1680 PCV2 open reading frame 2 (ORF2) sequences were compared and analyzed by methods of Neighbor-Joining, Maximum Likelihood, Bayesian inference and network analysis. Four distinct clades were consistently identified and included PCV2a, PCV2b, PCV2c and PCV2d; the p-distance between PCV2d and PCV2b was 0.055±0.008, larger than the PCV2 genotype-definition cut-off of 0.035, supporting PCV2d as an independent genotype. Among the 1680 sequences, 278-285 (16.5-17%) were classified as PCV2a, 1007-1058 (59.9-63%) as PCV2b, three (0.2%) as PCV2c, and 322-323 (19.2%) as PCV2d with the remaining 12-78 sequences (0.7-4.6%) classified as intermediate clades or strains by the various methods. Classification of strains to genotypes differed based on the number of sequences used for the analysis indicating that sample size is important when determining classification and assessing PCV2 trends and shifts. PCV2d was initially identified in 1999 samples in Switzerland, now appears to be widespread in China and has been present in North America since 2012. During 2012-2013, 37% of all investigated PCV2 sequences from U.S. pigs were classified as PCV2d and overall data analysis suggests an ongoing genotype shift from PCV2b towards PCV2d. The present analyses further indicate that PCV2d has emerged approximately 20 years ago.

Original languageEnglish
JournalJournal of General Virology
Volume96
Issue number7
DOIs
Publication statusPublished - 1 Jul 2015

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