Regional comparison of mosquito bloodmeals in South Australia: implications for Ross River virus ecology

Ross River virus (RRV) is responsible for the most notifications of human arboviral infection in Australia. Seroprevalence and experimental infection studies have implicated macropods (e.g., kangaroos) as the major reservoir hosts. However, transmission ecology varies spatially, and infections in urban areas have prompted the question of what animals serve as reservoirs in regions where macropods are scarce. In South Australia (SA), human infection rates for RRV vary greatly by region as do vector and reservoir abundance. We hypothesized that mosquito abundance and feeding patterns would vary among ecoregions of SA and could help explain divergent human case rates. To test our hypothesis, we amplified and sequenced a 457 base pair region of the cytochrome B segment of mitochondrial DNA from blood fed mosquitoes collected in three main ecoregions of SA and identified sequences using a BLAST search in NCBI. Domestic livestock made up the vast majority of bloodmeals from the region with the highest human infection rate. Livestock are generally not considered to be important reservoir hosts for RRV, but our results suggest they may have a role in transmission ecology in some places. Surprisingly, none of the 199 bloodmeal samples were identified as macropod in origin. In the context of these findings, we consider the possible RRV vectors and reservoir hosts in these regions and propose that diverse spatial and temporal transmission ecologies occur in SA, depending on vector and reservoir availability.