Genetic diversity of the ORF5 gene of porcine reproductive and respiratory syndrome virus (PRRSV) genotypes I and II in Thailand

To investigate the genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) in Thailand, 279 ORF5 sequences of PRRSV collected during 2010-2011 from 102 swine herds in five swine-producing areas were analyzed. The co-existence of European (EU) and North American (NA) genotypes was observed in 98 % of herds investigated and was evident at the pig level. Both genotypes have evolved separately with a temporal influence on strain development. Novel introductions influence the genetic diversity of the NA genotype. Although Thai EU and NA isolates develop their own clusters that are separate from those of other countries, there was no geographic influence on strain development within Thailand.