Mosquito life-history responses to vector control measures and their implications for malaria transmission risk
Half of the world's population is at risk of malaria. In 2012, there were >200 million cases and 627,000 malaria deaths. Since 2000, malaria mortality rates have been reduced by 45% globally in large part due to the upscaling of control measures targeted at mosquito vectors (Anopheles species), primarily long-lasting insecticide-treated bed-nets (LLINs) and indoor residual spraying (IRS).
Inevitably, mosquito populations exhibit evolutionary responses to these control measures, most notably the emergence of mosquitoes that are physiologically resistant to insecticides. However, theory leads us to predict additional subtle yet perhaps profoundly important evolutionary changes could occur in populations subject to such stringent control measures.
For example, selection arising from control measures could generate shifts in the behaviour or life-history of mosquito vectors in ways that could also influence, and most notably, help suppress transmission. Disease ecologists have only recently started to investigate these alternative responses, with the greatest focus being on mosquito behavioural changes that could reduce control effectiveness.
However, there is good evidence from other insect systems that population-wide increases in the extrinsic mortality rate of a similar magnitude as to those generated by vector control can induce a shift in life-history by altering the trade-off between investment in early reproduction versus long-term survival. If a similar phenomenon occurs in malaria mosquitoes it could substantially alter their ability to transmit parasites.
Almost nothing is known about life-history responses of malaria vectors to control measures and their implication for malaria transmission risk.
The overall goal of this project is to fill this critically important knowledge gap by investigating the evolutionary life-history adaptations of African
malaria-carrying mosquitoes to vector control, and associated impacts on their ability to transmit the disease.
To achieve this, the project will include ecological, evolutionary and molecular analyses of mosquito adaptations to increased adult mortality risk, as expected to arise from current levels of LLIN/IRS usage in transmission settings. Such information will be vital to predict the sustainability of current control measures and guide the implementation of future control strategies.
First published: 22 August 2014