Impact of Dryland Salinity on Population Dynamics of Vector Mosquitoes (Diptera: Culicidae) of Ross River Virus in Inland Areas of Southwestern Western Australia

Clearing of native vegetation for agriculture since European settlement has left 1.047 million ha of southwestern Australia affected by a severe form of environmental degradation called dryland salinity, characterized by secondary soil salinization and waterlogging. This area may expand by a further 1.7-3.4 million ha if current trends continue. Detailed investigations of seasonal of adult and larval mosquito population dynamics were undertaken in the region to test the hypothesis that the development of dryland salinity and waterlogging in inland southwestern Australia has led to a succession of mosquito species and increased Ross River virus (family Togaviridae, genus Alphavirus, RRV) transmission risk. Aedes (Ochlerotatus) camptorhynchus (Thomson) made up >90% of adult mosquito collections in saline regions. Nonmetric multidimensional scaling and generalized estimating equations modeling demonstrated that it was strongly associated with increasing severity of dryland salinity. This article describes the first detailed investigation of the mosquito fauna of inland southwestern Australia, and it is the first description of the influence of secondary soil salinity on mosquito population dynamics. Despite the dominant presence of Ae. camptorhynchus, RRV disease incidence is not currently a significant population health priority in areas affected by dryland salinity. Potential limiting factors include local climatic impacts on the seasonal mosquito population dynamics, vertebrate host distribution and feeding behavior of Ae. camptorhynchus, and the scarce and uneven distribution of the human population in the region.