Phylogenetic analysis of rabbit hemorrhagic disease virus in China and the antigenic variation of new strains.

This study aimed to investigate rabbit hemorrhagic disease virus (RHDV) in China. VP60 sequences of five RHDVs collected by our team, as well as those of 16 other published Chinese RHDV strains, were analyzed. Polygenic analysis using MEGA 4 software showed that 20 of the 21 Chinese strains could be clustered in the RHDVa subgroup, and WX/China/1984 was different from them. The Chinese RHDV strains were further classified into four subgroups, CH1 to CH4. Subgroup CH1, represented by the WX/China/1984 strain, was not prevalent in China after the first RHDV epidemic strain was reported. The CH2, CH3, and CH4 subgroups were far different from the CH1 subgroup, formed three separate clusters, and were distributed according to the time the strains were collected. Recently collected strains formed a new subgroup (CH4), represented by new RHDV varieties identified by challenging immunized rabbits and by comparison of genomic sequences. The present work is the first comprehensive analysis of Chinese RHDV and reveals a new RHDV variation that should be carefully monitored.