Characterization of genome segments 2, 3 and 6 of epizootic hemorrhagic disease virus strains isolated in Japan in 1985-2013: Identification of their serotypes and geographical genetic types.

We characterized genome segments 2, 3 and 6 (Seg-2, Seg-3 and Seg-6) of 11 Japanese strains of epizootic hemorrhagic disease (EHD) virus (EHDV) isolated in 1985-2013. The Japanese strains were divisible into two groups based on phylogenetic analyses of the nucleotide sequences of Seg-2 and Seg-6. In both of the phylogenetic trees based on Seg-2 and Seg-6, seven of the 11 Japanese strains were grouped together with EHDV-2 and EHDV-7 strains, and the other four Japanese strains were grouped with EHDV-1 strains. The phylogenetic analysis of Seg-2 among EHDV strains identified 10 of the 11 Japanese strains as EHDV-1, EHDV-2 or EHDV-7. The other Japanese strain, ON-4/B/98, isolated from an asymptomatic cow in 1998 was in the same group as the EHDV-2 and EHDV-7 strains in the phylogenetic trees based on Seg-2 and Seg-6, but the results suggested that the strain belongs to another serotype. We thus conducted a serum neutralization test to identify that serotype by using anti-EHDV-2 and anti-EHDV-7 rabbit sera. We observed that the ON-4/B/98 strain was not sufficiently neutralized by any of the antisera, which suggests that the strain could be assigned into a new serotype, tentatively named 'EHDV-10.' Sequences of Seg-3 were also determined, and all of the Japanese strains were grouped together with Australian strains, suggesting that the Japanese strains are a part of EHDV distributed in the Asia-Pacific region. The data obtained herein would be beneficial for the diagnosis and prevention of EHD in Japan and neighboring countries.