Bluetongue virus vector potential of selected Culicoides species in southern Australia

Summary

​Bluetongue virus (BTV) can cause catastrophic losses in sheep and goat populations. It is endemic in cattle across much of northern and eastern Australia with this distribution leaving the temperate zones free of virus. In 2006, the European livestock industry experienced a massive BTV outbreak occurring in previously free zones. To asses the risk of BTV outbreak in temperate zones of Australia, we have sampled Culicoides in various environments but focusing in cattle and sheep Victorian farms. The Culicoides distribution and taxonomy was updated, highlighting new cryptic species and minor incursions of specimens from neighbouring states. With a novel baiting method and molecular blood meal analysis, the feeding behaviour of endemic species was found oriented towards marsupials and birds but do not exclude bites on cattle and sheep. Quantitative PCRs run on C. austropalpalis individuals experimentally challenged against BTV serotype 1 did not find any viral RNA replication. The risk analysis performed for the main Culicoides species shows a low or null risk. The evidence of cryptic species has limited the analysis depth for these groups. However our data have restricted the gap in the knowledge hampering the understanding and capacities in mitigation for BTV incursion.