Full-Genome Sequencing as a Basis for Molecular Epidemiology Studies of Bluetongue Virus in India

Abstract

Since 1998 there have been significant changes in the global distribution of bluetongue virus (BTV). Ten previously exotic BTV serotypes have been detected in Europe, causing severe disease outbreaks in naïve ruminant populations. Previously exotic BTV serotypes were also identified in the USA, Israel, Australia and India. BTV is transmitted by biting midges (Culicoides spp.) and changes in the distribution of vector species, climate change, increased international travel and trade are thought to have contributed to these events. Thirteen BTV serotypes have been isolated in India since first reports of the disease in the country during 1964. Efficient methods for preparation of viral dsRNA and cDNA synthesis, have facilitated full-genome sequencing of BTV strains from the region. These studies introduce a new approach for BTV characterization, based on full-genome sequencing and phylogenetic analyses, facilitating the identification of BTV serotype, topotype and reassortant strains. Phylogenetic analyses show that most of the equivalent genome-segments of Indian BTV strains are closely related, clustering within a major eastern BTV ‘topotype’. However, genome-segment 5 (Seg-5) encoding NS1, from multiple post 1982 Indian isolates, originated from a western BTV topotype. All ten genome-segments of BTV-2 isolates (IND2003/01, IND2003/02 and IND2003/03) are closely related (>99% identity) to a South African BTV-2 vaccine-strain (western topotype). Similarly BTV-10 isolates (IND2003/06; IND2005/04) show >99% identity in all genome segments, to the prototype BTV-10 (CA-8) strain from the USA. These data suggest repeated introductions of western BTV field and/or vaccine-strains into India, potentially linked to animal or vector-insect movements, or unauthorised use of ‘live’ South African or American BTV-vaccines in the country. The data presented will help improve nucleic acid based diagnostics for Indian serotypes/topotypes, as part of control strategies.

Identification and genomic characterization of the first isolate of bluetongue virus serotype 5 detected in Australia

“…However, the rapid output from next‐generation nucleic acid sequencing technologies has enabled the development of BTV‐specific quantitative reverse transcriptase polymerase chain reaction (RT‐PCR) assays which, together with the application of phenotyping software algorithms, play an increasingly significant role in initial BTV detection and serotype confirmation (Maan et al . , ; Rao et al . , ).…”

“…; Maan et al . ; National Arbovirus Monitoring Program ). Despite the prolonged presence of BTV in Australia, there have been no reports of established bluetongue disease in commercial sheep populations.…”

Prevalence and risk factors for bluetongue in the State of São Paulo, Brazil

“…To date, 27 serotypes have been widely recognized, and two new putative serotypes, BTV‐28 and BTV‐29, have been proposed (Maan et al . ; Bumbarov et al . ; Sun et al .…”

Whole Genome Sequence Analysis of Bluetongue Virus Serotype 12 from Northern India

“…the outer capsid formed by VP2 and VP5, VP7 forms the core and VP3 forms subcore. The viral genome encodes 7 structural (VP1 to VP7) and 5 non-structural (NS1, NS2, NS3/ NS3a, NS4 and NS5 [S-10 ORF-2]) proteins (Pullenger et al, 2016, Maan et al, 2015. Apart from horizontal and vertical transmission, the virus is mainly transmitted biologically by Culicoides sp.…”

“…BTV-12 has been isolated and sequenced earlier from Andhra Pradesh, one of the southern states of India in 2011 (Rao et al, 2015). BTV-12 has been previously reported from South Africa, Kenya, Japan and Taiwan.…”