Geographic distribution and evolution of Sindbis virus in Australia.

Abstract

The molecular epidemiology and evolution of Sindbis (SIN) virus in Australia was examined. Several SIN virus strains isolated from other countries were also included in the analysis. Two regions of the virus genome were sequenced including a 418 bp region of the E2 gene and a 484 bp region containing part of the junction region and the 5h end of the C gene. Analysis of the nucleotide and deduced amino acid sequence data from 40 SIN virus isolates clearly separated the Paleoarctic/ Ethiopian and Oriental/Australian genetic types of SIN virus. Examination of the Australian strains showed a temporal rather than geographic relationship. This is consistent with the virus having migratory birds as the major vertebrate host, as it allows for movement of virus over vast areas of the continent over a relatively short period of time. The results suggest that the virus is being periodically redistributed over the continent from an enzootic focus of evolving SIN virus. However, SIN virus strains isolated from mosquitoes collected in the south-west of Australia appear to represent a new SIN virus lineage, which is distinct from the Paleoarctic/Ethiopian and Oriental/Australian lineages. Given the widespread geographic dispersal of the Paleoarctic/ Ethiopian and Oriental/Australian lineages, it is surprising that the South-west genetic type is so restricted in its area of circulation. Nucleotide sequence data from the C gene of the prototype strain of the alphavirus Whataroa were also determined. This virus was found to be genetically distinct from the SIN virus isolates included in the present study ; however, it is clearly SIN-like and appears to have evolved from a SIN-like ancestral virus.

Evolutionary Relationships and Systematics of the Alphaviruses

“…Unrooted phylogenetic tree of Alphavirus species generated from complete structural polyprotein amino acid sequences by using the neighbor-joining program (61). Virus abbreviations are found in Table 1 (37,54). Host mobility presumably limits virus diversity by preventing geographic isolation and allopatric divergence and by favoring competitive exclusion of closely related viruses that are mixed over large geographic ranges.…”

Isolation of Japanese encephalitis virus from mosquitoes (Diptera: Culicidae) collected in the Western Province of Papua New Guinea, 1997-1998.

“…34,35 Nucleotide sequence analysis of the E2 and C genes of an isolate of a 1966 isolate of SIN virus from northern PNG was shown to be more closely related to the Oriental/ Australasian genotype of SIN virus than to the Paleoarctic/ Ethiopian genotype. 36 If nucleotide sequence analysis reveals the strain of SIN virus circulating in transmission cycles in PNG is similarly related to the Oriental/Australasian genotype, it is unlikely to pose a risk for people living in PNG.…”

Isolation and Phylogenetic Analysis of Sindbis Viruses from Mosquitoes in Germany

“…Birds of the orders Passeriformes and Anseriformes are counted among the main hosts of the virus and have been shown to be responsible for the geographic distribution of SINV and the possible introduction of SINV to so-far-uninfested areas (5). Phylogenetic analysis of the nucleotide sequence data of several SINV strains demonstrated two distinct genetic lineages (paleoarctic/Ethiopian and oriental/Australian) (7,14). It was not known if SINV circulates in Germany, and therefore, the natural vectors of SINV and the geographic distribution of SINV in its vectors have remained unknown as well.…”