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Bluetongue (BT) is one of the most important insect-borne, non-contagious viral diseases of ruminants and can cause severe disease and death in sheep. Its pathogen, bluetongue virus (BTV) has a double-stranded RNA genome consisting of 10 segments that provides an opportunity for field and vaccine strains of different serotypes to reassort whilst simultaneously infecting the same animal. For the first time, we report the full-length genome sequence of a BTV strain of serotype 21 (5149E) isolated from sentinel cattle in Guangxi Province in China in 2015. Sequence analysis suggested that the isolate 5149E had undergone a reassortment incident and acquired seg-6 from an isolate of BTV-16 which originated from Japan. This study aims to provide more understanding as to the origin and epidemiology of BTV.

A Chuzan virus (CHUV), defined as GX871 here, was isolated from blood from a sentinel cattle firstly in China, and its full-length genome was sequenced in this study. The GX871 genome included 10 segments and 18914 bp, one base fewer than the CHUV prototype strain K-47 due to a one-base deletion in the 5' non-coding region of segment 8. A frameshift mutation was detected in a short coding region (1010-1026 nt) corresponding to the VP1 protein; this frameshift resulted in a five-amino acid mutation from 336CVLSY340 to 336YGAKL340. In addition, there were a one-base deletion at 1713 nt and a one-base insertion at 1682 nt in the 3' non-coding region of segment 5. Based on phylogenetic analysis of the deduced VP2 amino acid sequences, Palyam serogroup viruses were classified into three groups. The Chinese CHUV isolate GX871 was categorized into the same group as CHUV prototype strain K-47. The phylogenetic tree was divided into three clusters according to the geographical distribution of the partial nucleotide sequences of VP7, and this arrangement might define the geographical gene pool of CHUV.