Isolation, Identification, and Molecular Evolutionary Analysis of Infectious Hematopoietic Necrosis Virus (IHNV) from Farmed Rainbow Trout in Southwest China

IHNV troubled the salmon breeding industry in China for years, and it often causes large-scale deaths. To study the disease characteristics of IHNV and its epidemiology in China， this study isolated and sequenced the Whole genome of an IHNV strain (IHNV-SCCD) (GenBank No： OQ801357) from farmed diseased rainbow trout in Chengdu and compared 99 IHNV strains from China by mega.11. The IHNV-SCCD strain was isolated by using EPC cells. The complete genome sequence was determined and deposited in the NCBI database. Phylogenetic analysis showed that IHNV-SCCD belongs to the typical J gene group, recently with Sichuan strains. Except for BjLL strain and LN12-17 strain, the remaining 98 strains followed a single evolutionary path. Note that IHNV in Liaoning province is the fastest evolutionary. In addition to the geographical differences, the Xinjiang strains were closely related to the Yunnan strains, and some strains from Beijing were closely related to some strains from Sichuan. There were two evolutionary branches in Gansu and Qinghai; QH17, isolated from Qinghai, was most closely related to SX1704 from Shaanxi. These results suggest that the prevalence of IHNV in China was extremely wide, and the evolution rate was fast. It is necessary to strengthen the monitoring and prevention methods.