MARC

Ross River virus (RRV) is the most common mosquito arbovirus affecting humans in Australia. Approximately 5000 human cases are reported annually. The transmission cycle of RRV is complex, with at least a dozen mosquito vectors and a diverse but poorly understood reservoir host community that may include macropods, humans, possums and birds. These factors, combined with the circulation of multiple RRV strains of varying virulence, make outbreak prediction and the formation of public health mitigation strategies difficult. Research priorities include:

• The phylogeny and spatiotemporal importance of RRV variants.
• The genetic and environmental determinants of vector competence.
• Transmission pathways of RRV in urban, peri-urban and rural habitats.
• Development of novel surveillance technologies and predictive models to better understand transmission dynamics and pre-empt outbreaks.
• Development of novel disease and mosquito control strategies.

Globally, urban development is concentrated along the world’s coasts yet urban planning guidelines often overlook the problems that human encroachment on or near coastal mosquito habitat may cause. Developments near breeding sites (e.g. coastal marshes and mangrove swamps) will create potentially unbearable mosquito (and/or biting midge) biting burdens for residents unless effective measures are taken. This also has public health implications where the species in question include competent disease vectors. Research priorities include:

• The effectiveness of vegetation barriers and open-space buffer zones in reducing biting pressure in residential developments close to aquatic habitats.
• Improved water sensitive urban design (WSUD), such as swales and bioretention basins, to eliminate mosquito breeding or facilitate mosquito control while improving the quality of storm water discharge.
• Community perceptions of nuisance, the cost-benefit of implementing protective measures against biting insects and the willingness of residents to implement those measures.

Southeast Queensland is threatened by two invasive mosquito vectors: Aedes aegypti and Aedes albopictus. Aedes aegypti, the primary dengue vector, was present in Brisbane into the 1950s. It is not entirely clear why the population disappeared, but it may re-establish from North Queensland or from various remnant pockets in the South East. Incursions from overseas also threaten the establishment of exotic, insecticide-resistant variants in Australia. Aedes albopictus is not on mainland Australia but it is highly invasive and present throughout the Torres Strait islands. The movement of eggs from the Torres Strait to the mainland in shipping containers or personal effects, and the species subsequent establishment in urban areas, remains a tremendous risk. Mainland Australia requires effective mosquito surveillance programs both in and outside of first ports of entry to reduce establishment risks. Research priorities include:

• Innovative adult and larval surveillance strategies.
• Effectiveness of current mitigation strategies in ports of entry and approved arrangement facilities.
• Evaluation of alternative control tools at ports or as part of elimination plans.
• The use of population genetics to understand incursion pathways and the risks of Aedes aegypti expansion within Queensland.
• Insecticide resistance monitoring and management.
• The role of drought and human behaviour e.g. the mass installation of rainwater tanks and hoarding of water) in the maintenance of urban Aedes mosquitoes.

Mosquito management programs in Southeast Queensland emphasise larval control in breeding sites with the use of target-specific compounds such as Bacillus thuringiensis israelensis (Bti) and S-methoprene, but there are also situations where adult management is appropriate. Vegetation barrier or harbourage treatments may be effective where residential zones are adjacent to breeding sites that are inaccessible for larval control, but their efficacy requires evaluation. The volatile pyrethroids (i.e. metofluthrin or transfluthrin) may have indoor and outdoor applications against mosquitoes or biting midges. Research priorities include:

• Efficacy of new formulations of thermal fogs and ultra-low volume sprays against mosquitoes and biting midges.
• Trials of the repellency of spatial volatiles (e.g., metofluthrin and transfluthrin) against mosquitoes indoors and outdoors.
• The effectiveness of vegetation barriers and residential harbourage spraying in reducing biting insect pressure in residential developments.

Two freshwater mosquito species implicated in the transmission of Ross River virus (RRV) are Culex annulirostris and Aedes procax. Larvae of the former occur in a number of habitat types including temporary grass-dominated pools and permanent freshwater ponds, often on private land. The latter’s habitat is poorly described. Local governments require a greater understanding of the role that these species play in RRV transmission, their most productive habitats and the effective management of these sites. Research priorities include:

• The ecology, biology and habitat associations of Culex annulirostris and Aedes procax.
• Impact of land use and land cover change on species distributions.
• Effectiveness of biological (e.g. Bacillus thuringiensis israelensis) and chemical control strategies (e.g. S-methoprene).
• The implementation of improved water sensitive urban design (WSUD) and urban planning strategies to eliminate mosquito breeding.

Aedes vigilax is the most pestiferous mosquito in Southeast Queensland, particularly near the saltmarsh pools and mangrove swamps where they thrive. They are persistent biters, can disperse for long distances (>5km) and are suspected vectors of Ross River and Barmah Forest viruses. Their great dispersal capacity makes them a concern for new housing developments near coastal habitat. Research priorities include:

• Magnitude and frequency of dispersal of Aedes vigilax from coastal breeding sites to adjacent human developments.
• Determination of the spatial and environmental factors influencing the efficacy and persistence of Bacillus thuringiensis israelensis applications to control larval populations.
• Development of novel adult control and surveillance strategies, including investigations into the sugar-feeding behaviours of Aedes vigilax.
• Use of emerging technology (e.g. unmanned aerial vehicles) in larval control and identification, classification and mapping of mosquito breeding habitat.
• The impact of sea level rise and mangrove transgression into saltmarsh environments on the ecology and biology of Aedes vigilax.
• Environmental management strategies, e.g. runnelling and open marsh water management (OMWM), to reduce mosquito productivity while minimising environmental impacts.