Isolation of bluetongue virus serotype 1 (BTV-1) from goats and its phylogenetic relationship to other BTV-1 isolates worldwide based on full-length sequence of genome segment-2

Eight bluetongue viruses (BTV) were isolated in BHK-21 cell culture from blood of goats suffering from peste des petits ruminants. These viruses were identified as BTV serotype 1 (BTV-1) by RT-PCR using VP2-gene-based primers coupled with sequencing of the PCR products. All of the isolates showed similar genome migration profile in 8% polyacrylamide gel electrophoresis. The genome segment-2 (seg-2) of one isolate (MKD18/India/2008) was amplified piecemeal by overlapping PCR, and the products were sequenced to obtain full-length seg-2. Phylogenetic analysis based on the seg-2 sequence revealed that MKD18 is closely related to Australian BTV-1 isolates, with 86.3–86.8% nucleotide identity. Phylogenetic analysis based on the partial sequence of seg-2 (541 bp, nucleotides 1,304–1,844) showed that the Indian BTV-1 isolates, namely, MKD18, Avikanagar, Sirsa-3 and Chennai, are very closely related to each other, with more than 99.6% nucleotide identity. Although a high degree of similarity exists, the Indian BTV-1 isolates collected over the past 25 years should be studied to demonstrate the co-existence of different VP2 antigenic profiles.