Mosquito vectors of ross river virus, a simulation model of thermal mortality and development in a tidal urban saltmarsh environment in Southwest Western Australia
Date of Award
Edith Cowan University
Doctor of Philosophy
School of Medical and Health Sciences
This research synthesizes and extends the large body of work on the distribution, ecology, and physiology of the three mosquito vectors of Ross River virus, Culex annulirostris Skuse, Aedes vigilax (Skuse) and Aedes camptorhynchus (Thomson), using mathematical modelling and simulation methods. Computational techniques developed for malaria vector development and physiological research of other mosquito-borne disease vectors have been adapted and applied to a temperate saltmarsh environment located in the Swan River catchment in Southwest Western Australia.
The simulation has two compartments, a hydrological compartment which predicts water-body height and water temperature using a one-layer energy budget model developed for small scale shallow-water bodies and modifies it to minimise error attributable to parametrisation of latent heat flux. Real world performance was assessed against on-site field measurement for water depth and temperature, and against three other methods for estimation of water temperature; the original unmodified energy balance model, estimation of water temperature based on air temperature and waterbody volume, and by using air-temperature as a direct proxy for water temperature.
The second compartment models mosquito development from egg through larval and adult stages, using a series of equations. Species-specific physiological parameter values were applied from the large body of laboratory and field studies for these three mosquito species. The main driver of mosquito development examined was thermal development. The simulation model accurately predicts hourly shallow-water body temperature, and the timing and relative magnitude of mosquito population peaks for the three species across seasons and years. The main limitations identified were due to insufficient studies on the thermal development and mortality limits, particularly for the two Aedes species. The model is sensitive to the minimum egg-hatching temperature thresholds and maximum temperature mortality limits at adult and larval stages.
A range of climate change projection datasets were used as inputs to the final simulation model to examine possible effects of sea-level and air temperature changes from 2030 to 2070, under two Representative Concentration Pathways, RCP 4.5, and RCP 8.5. It is expected that populations of both Aedes species will increase in magnitude, mainly driven by increased sea-level height and the resultant increased frequency of tidal inundation of the saltmarsh. All three species will have extended active seasons due mainly to increased air-temperature under climate change scenarios. Of the climate change variables used in the analysis, the rate of sea-level rise, coupled with the rate of sedimentation or accretion at the wetland surface had a significant effect on the magnitude of change to species population numbers.
This simulation algorithm can be a useful tool in mosquito management programs and is also able to be adapted to invertebrates with aquatic stages in a wide range of environmental and climatic regions, both across Australia and internationally, particularly those with larval stages in large natural water bodies such as ephemeral fresh water sites, and shallow tidal locations.
Access to this thesis is embargoed until 7th November 2024.
Staples, K. (2023). Mosquito vectors of ross river virus, a simulation model of thermal mortality and development in a tidal urban saltmarsh environment in Southwest Western Australia. Edith Cowan University. https://doi.org/10.25958/ry27-6q68