Molecular epidemiology of pseudorabies virus in Yunnan and the sequence analysis of its gD gene

Outbreaks of pseudorabies (PRs) have occurred in Yunnan, China, which caused significant economic loss. To determine the prevalence and origin of PR in Yunnan, especially among vaccinated pigs, overall 791 samples of blood, tissue, semen, and sera were analyzed by serological methods, PCR, and sequence analysis of gD gene. Detection with viral gI antibody or PCR showed that the yearly positive rates of PR virus (PRV) in Yunnan from 2010 to 2014 were 48.15, 21.26, 2.17, 5.22, and 0.35%, respectively, with an average of 15.43%. In general, the incidence declined through the period of 2010-2014 probably due to the application of PRV eradication strategies. A phylogenetic tree was constructed based on the complete sequence of gD gene, with all strains clustered into two independent clades, i.e., Asian and European-American clades. The virus isolates from Henan, Tianjin, Heilongjiang, Sichuan, Shandong, Fujian, Xinjiang, Hubei, Guangdong, and Yunnan fell into Asian group, which harbored South Korea isolate. Four Yunnan virus isolates together with South Korean Namyangju fell into in the European-American clade. It showed that PR was pandemic as there was not a clear clue about the geographical origin of the PRV isolates in China since 2010.