Molecular epidemiological and genetic characterization of pseudorabies virus in Guangxi, China

Abstract

Pseudorabies virus (PRV) is an important pathogen that can cause harm to the pig population. However, there have been a number of large-scale outbreaks of pseudorabies on Chinese farms where animals have been previously vaccinated with the Bartha-K61 vaccine since 2011. In order to understand the epidemiological trend and genetic variations of PRV in Guangxi province, China, 819 tissue samples were collected from swine farms suspected of PRV infection from 2013-2019. In this study, these were tested for infectious wild strains of PRV. The results showed a positive rate of PRV in Guangxi province of 28.21% (231/819). 36 wild-type PRV strains were successfully isolated from the PRV-positive tissue samples, and a genetic evolutionary analysis was performed based on the gB, gC, gD, gE and TK genes. 30 of the PRV strains were clustered with the Chinese variant strains, HeN1-China-2012 and HLJ8-China-2013. In addition, 5 PRV strains were genetically related to the Chinese classical strains, and one isolate was a recombinant strain of the PRV variant and the vaccine strain, Bartha-K61. Amino acid sequence analysis showed that all 36 PRV strains had characteristic variant sites in the amino acid sequences of the gB, gC, gD and gE proteins. Pathogenicity analysis showed that, compared to the PRV classical strains, the PRV variant strains had a stronger pathogenicity in mice together with a lower LD 50 . Taken together, our results showed that wild-type PRV infections are common in pig farms in the Guangxi province of China, and that the dominant prevalent strains were those of the PRV variants. The PRV variant strains also had a stronger pathogenicity in mice. Our data will provide a useful reference for understanding the prevalence and genetic evolution of PRV in China.