02313     2200265   4500001002100000005001500021035002000036007000300056008003900059082001500098084001500113245010300128260003200231300000600263650002100269700002100290700002500311700002200336700002300358700002000381700001900401700002300420700002300443520158100466INLIS00000000001919120240911125055  a0010-0924000270ta240911                |          | |    aARTVET2371  aARTVET2371  aGenomic analysis of bluetongue virus  episystems in Australia and Indonesia /cCadhla Firth1,2*  bFirth et al. Vet Res,c2017  a9 4aGenomic analysis0 aKim R. Blasdell10 aRachel Amos?Ritchie30 aIndrawati Sendow40 aKalpana Agnihotri50 aDavid B. Boyle30 aPeter Daniels30 aPeter D. Kirkland60 aPeter J. Walker3,7  aThe distribution of bluetongue viruses (BTV) in Australia is represented by two distinct and interconnected epidemio?
logical systems (episystems)—one distributed primarily in the north and one in the east. The northern episystem is 
characterised by substantially greater antigenic diversity than the eastern episystem; yet the forces that act to limit the 
diversity present in the east remain unclear. Previous work has indicated that the northern episystem is linked to that 
of island South East Asia and Melanesia, and that BTV present in Indonesia, Papua New Guinea and East Timor, may act 
as source populations for new serotypes and genotypes of BTV to enter Australia’s north. In this study, the genomes 
of 49 bluetongue viruses from the eastern episystem and 13 from Indonesia were sequenced and analysed along 
with 27 previously published genome sequences from the northern Australian episystem. The results of this analysis 
confirm that the Australian BTV population has its origins in the South East Asian/Melanesian episystem, and that 
incursions into northern Australia occur with some regularity. In addition, the presence of limited genetic diversity 
in the eastern episystem relative to that found in the north supports the presence of substantial, but not complete, 
barriers to gene flow between the northern and eastern Australian episystems. Genetic bottlenecks between each 
successive episystem are evident, and appear to be responsible for the reduction in BTV genetic diversity observed in 
the north to south–east direction.