Isolation and molecular characterization of bluetongue virus from asymptomatic goats

Five bluetongue viruses (BTV) were isolated in BHK-21 cell culture from blood of asymptomatic and peste des petits ruminants virus infected goats. These viruses were identified as BTV serotype 1 (BTV-1) by RT-PCR using VP2gene-based primers coupled with sequencing of the PCR products. All of the isolates showed 10 bands of dsRNA in 10% polyacrylamide gel electrophoresis that is typical of BTV. In sequencing, out of five isolates, three sequences (PTG-13, G53 and LRS-1) were very closely related with 99% nucleotide identity amongst them determined based on 886-bp sequence of 5’ end of the VP2 gene. These isolates were related to other Indian BTV-1 isolates (MKD-18, SKN-7 and SKN-8) with a nucleotide identity of 99.7%. Isolate G-53 was very closely related to SKN-8 (99.7% nucleotide identity), whereas, PTG13 and MKD-18 appeared identical. LRS-1, SKN-7 and MKD-18 were also identical. Phylogenetically, all the Indian BTV1 isolates constituted a single clade which is distinct from the European, Australian and South African isolates. Indian isolates are more closely related to the Australian isolates.