Genomic analysis of bluetongue virus episystems in Australia and Indonesia

Abstract

The distribution of bluetongue viruses (BTV) in Australia is represented by two distinct and interconnected epidemiological 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.Electronic supplementary materialThe online version of this article (10.1186/s13567-017-0488-4) contains supplementary material, which is available to authorized users.

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

“…Additionally, the majority of BTV serotypes appear to be exclusively concentrated in the far northern regions of the Northern Territory and Western Australia, with a more limited group of serotypes periodically entering Northern Queensland (BTV‐1, ‐2, ‐15, ‐16, ‐21) with only BTV‐1 and ‐21 being consistently isolated in greater Queensland and further south in New South Wales, over a prolonged time period (Firth et al . ).…”

“…This is believed to be primarily due to the major sheep grazing areas existing in the south of the country where there is very limited and/or sporadic overlap with the known range of the most widespread BTV competent vector in Australia, Culicoides brevitarsis (St.George 1985;Standfast et al 1992). Additionally, the majority of BTV serotypes appear to be exclusively concentrated in the far northern regions of the Northern Territory and Western Australia, with a more limited group of serotypes periodically entering Northern Queensland (BTV-1, -2, -15, -16, -21) with only BTV-1 and -21 being consistently isolated in greater Queensland and further south in New South Wales, over a prolonged time period (Firth et al 2017).…”

Ecological Dynamics Impacting Bluetongue Virus Transmission in North America

“…Bluetongue virus (BTV) is the etiologic agent of bluetongue (BT), an economically important arboviral disease of wild and domestic ruminants that is transmitted by various species of Culicoides midges (4-7). The expansion of Culicoides-transmitted arboviral diseases (BT, epizootic hemorrhagic disease [EHDV], Schmallenberg) on essentially every continent confirms that these diseases constitute a growing threat to ruminant communities (8)(9)(10)(11)(12)(13). They also have substantial economic consequences.…”

“…Novel BTV serotypes have also recently been identified in historically enzootic countries or regions including the southeastern United States (US), South America, Israel, and Australia, reflecting diverse means for spread of these viruses between regions (13,(19)(20)(21)(22). Despite the link of climate change to recent incursions of BTV in Europe and expansion of geographic range in North America, there is limited information on how factors related to the ecology of BTV's vertebrate and invertebrate hosts might impact the evolution, distribution, and transmission dynamics of BTV (1,23,24).…”

The serologic investigation and viral isolation of bluetongue virus in Shangri‐La in Southwest China

“…All isolates were identified as the same strain, and one of the isolates (named YN/2017) was sequenced completely. Interestingly, the genome of BTV strain YN/2017 was almost identical to those of three Indonesia BTV‐21 strains (D151, RIVS‐66 and RIVS‐60; Table ) isolated in West Java during 1989 to 1990 (Firth et al, ). However, it was clearly different from the domestic strain 5149E, which was isolated in southern China in 2015 and was the first completely sequenced BTV‐21 strain in China (Qin et al, ).…”