Genetic characteristic analysis of ORF2 of Porcine circovirus type 2 (PCV2) in some provinces, Viet Nam, in the period 2007 - 2016

Abstract

Porcine circovirus type 2 (PCV2) is a causative agent relating to several porcine circovirus diseases
- PCVDs, causing heavy economic losses in the swine industry. With a high nucleotide substitution rate,
PCV2 continues to evolve and shift to novel genotypes. To determine the prevalence of PCV2 genotypes
in Viet Nam, full-length of ORF2 of 48 PCV2 isolates collecting from 13 provinces in Viet Nam in the
period from 2007 to 2016 was analysed to determine nucleotide sequence, build phylogenetic tree and
compare to PCV2 strains that reported in Viet Nam and other countries. The analysed results showed
that genotypes of PCV2b, PCV2d and recombinant cluster were co-existed and prevalent. Of which,
the most common was PCV2b (24/48) and the emergence of PCV2d, especially PCV2d2 (15/16). The
nucleotide similarity level of the PCV2 isolates classifying in the same genotype was relatively high,
such as: 98.7% - 100% for PCV2b, 98.5 - 100% for PCV2d2 and 98.7 - 100% for recombinant cluster.
Genetic divergence among the genotypes was also quite high ranging from 0.0595 ± 0.0096 to 0.0663
± 0.0102. Besides, genotype change by time had occurred at the farm level. These studied results
contribute to further clarification of PCV2 epidemiology in Viet Nam.