Comparing different approaches of modelling the effects of temperature and rainfall on malaria transmission in high and low transmission settings
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Background
Malaria transmission is primarily limited to tropical regions where environmental conditions are conducive for the development of Plasmodium parasites and Anopheles mosquitoes. Adequate rainfall provides breeding sites, while suitable temperatures facilitate mosquito life-cycles and parasite development. Evaluating the efficacy of vector control interventions, such as insecticide treated nets and indoor residual spraying, is crucial to determine their effectiveness in reducing malaria transmission. In this context, mathemati-cal modeling offers a valuable framework for understanding the impacts of these meteorological factors on malaria transmission and evaluating the efficacy of vector control interventions.
Methods
We develop a vector-host compartmental mathematical model to compare three published approaches to incorporating weather influences on malaria transmission. The first approach examines mosquito biting behavior and mortality rates in larval and adult stages. The second focuses on temperature effects on mosquito life-cycle characteristics during aquatic stages. The third considers how temperature and rainfall influence adult mosquito behavior, environmental carrying capacity, and survival during aquatic stages. The model is simulated with varying intervention efficacy for vector control to identify differences in predicted malaria incidence, prevalence, cases averted, and transmission dynamics.
Results
Simulation results for the same initial conditions and no vector control, indicate that prevalence stabilizes around 500 cases per 1000 for all modelling approaches. Increasing vector control efficacy significantly reduces prevalence for all approaches, with the first approach showing the most considerable reduction and the longest delay to the start of the transmission season. While malaria incidence peaks are highest for the second approach, more cases are averted when the first approach is adopted, followed by the second, then the third.
Conclusion
Adopting an approach that accounts for how rainfall influences mosquito environmental capacity and the temperature regulation of parasite development, but excludes aquatic stage development, limits the number of mosquitoes available to transmit the disease. Investigating temperature regulation of mosquito development and survival provides a detailed and reliable description of mosquito population dynamics but projects higher peaks in malaria incidence. In contrast, the approach that examines how temperature influences the biting rates, larval mortality, and adult mosquito mortality projects lower peaks but also demonstrates significant reductions in incidence and prevalence as vector control efficacy improves. While this approach offers a simplified model of the dynamics, they may underestimate actual mosquito population trends, thereby impacting the effectiveness of modeled interventions.
