Abstract: Porcine pseudorabies (PR) is an acute and hot infectious disease caused by pseudorabies virus (PRV). Since the end of 2011, PRV had been mutated. The traditional attenuated PRV vaccine can not provide complete protection for PRV mutants, which brings great challenges to the prevention and control of PRV in China. To understand the molecular characteristics of major virulence genes of PRV clinical epidemic strains in Anhui Province, PCR,cell-inoculation tests, transmission electron microscopy (TEM), indirect immunoinfluscent assay (IFA) and animal test were used to isolate and identify the pathogen. The major virulence genes (gE, gI, TK, gB, gC and gD) of PRV strains were cloned and sequenced by PCR with 6 pairs of specific primers. A total of 15 PRV strains of clinical cases were isolated and identified from Anhui Province during 2016-2018. The sequences of gE, gI, TK, gB, gC and gD genes of PRV were highly homologous with those of PRV mutants which were prevalent in China after 2011. Compared with the sequence of domestic PRV classical strains before 2011, there are multiple substitutions, insertions or deletions of multiple sites in the gE, gB, gC and gD gene sequences of PRV isolates, and some mutations were located in important epitope regions. The above results indicated that 15 PRV strains isolated from Anhui Province from 2016 to 2018 were all variant strains, which have become the main epidemic strains in Anhui Province. The gene sequences of gI and TK of 15 PRV isolates were relatively conservative, but the mutation of amino acids in the epitopes of gE and gC protein might change their virulence and antigenicity. The homology of PRV sequence between some PRV isolates from neighboring areas was 100%, which may be related to the frequent trans-provincial transfer and trans-regional introduction of pigs.

Key words: pseudorabies virus, isolation and identification, virulence gene, molecular characterization