BT is endemic in India, particularly in the South and BTV strains belonging to twelve BTV-serotypes (BTV-1, 2, 3, 4, 5, 9, 10, 12, 16, 21, 23 and 24) have been isolated since 2001. A pentavalent inactivated BTV vaccine containing serotypes 1, 2, 10, 16 and 23, is currently being used in the South. This study focusses on the isolation and the typing of BTV strains from Southern India, 2014-15, then generation of full length sequence data, primarily for BTV genome Seg-2 to provide molecular epidemiology information concerning the strains circulating in the region. Suspected field outbreaks of BTV from Telangana, Andhra Pradesh, Karnataka and Tamil Nadu states in Southern India during 2014-2015 were attended to collect well documented blood and necropsy clinical samples from mixed population of small ruminants and cattle. Of the 447 field samples (EDTA blood, spleen, lymph node and saliva), 236 gave positive results for BTV RNA by serogroup-specific real-time RT-PCR targeting Seg-9 and Seg-10 for 2014 and 2015 samples respectively. A total of 141 BTV virus isolations were made from 141 serogroup-specific qRT-PCR positive samples, by infecting KC and BHK cells. The isolated 63 BTVs were serotyped by qRT-PCR assay targeting Seg-2 of the BTV-1 to BTV-24, BTV-26, BTV-27 and BTV-29, confirming the current co-circulation of 7 BTV serotypes, including BTV-1, BTV-2, BTV-4, BTV-5, BTV-9, BTV-10 and BTV-12 in 62 BTV isolates. Dual and triple BTV co-infections with these serotypes were detected in 22 and 4 BTV isolates, respectively. None of the serotypes present in the pentavalent vaccine were identified in any of the 22 BTV isolates from vaccinated animals, suggesting that the vaccine was indeed effective against the homologous serotype field strains. Among the 7 serotypes identified by Seg-2 based ORF sequence analysis of 46 BTV isolates (BTV-1, BTV-2, BTV-4, BTV-5, BTV-9, BTV-10 and BTV-12), 4 serotypes BTV-1, BTV-2, BTV-4 and BTV-9, belonged to eastern topotypes, whereas 3 serotypes, BTV-5, BTV-10 and BTV-12 were identified as western topotypes. For 4 BTV isolates, the serotype detected by qRT-PCR was different of that detected by NGS. The full genome sequencing and analyses is still ongoing in Glasgow. This data will assist in understand the epidemiology of the BT in India and implementation of effective BTV control to ensure the use of appropriate BTV serotype and strains in the available BT vaccine in India.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:754407 |
| Date | January 2018 |
| Creators | Yadav, Sarita |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/30807/ |
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