Comparing three approaches to modelling the effects of temperature and rainfall on malaria incidence in different climatic regions

Malaria transmission is primarily limited to tropical regions where environmental conditions are conducive for the survival of Plasmodium parasites and Anopheles mosquitoes. Adequate rainfall provides breeding sites, while suitable temperatures facilitate vector mosquito life-cycles and parasite development. Evaluating the efficacy of vector control interventions is crucial to determine their effectiveness in reducing malaria transmission. The aim of this study was to explore how these factors affect transmission dynamics at varying levels of vector control efficacy. We developed a vector-host compartmental mathematical model to compare three published approaches to incorporating weather influences on malaria transmission. The first approach examines mosquito biting behaviour and mortality rates in larval and adult stages. The second focuses on temper- ature effects on mosquito life-cycle characteristics throughout the aquatic and adult stages. The third considers how temperature and rainfall influence adult mosquito behaviour, environmental carrying capacity, and survival during the aquatic stages. Model simulations were conducted at different annual vector con- trol coverage levels, to identify variations in transmission patterns and seasonal variability in daily and annual incidence across three climate regions. The first approach indicates sustained seasonal transmission, with lower cases per 1,000 in tropical regions compared to semi-arid and sub-tropical regions, even with enhanced vector control reducing cases. The second approach projects extended seasonal peaks in malaria transmission in tropical and semi- arid regions, driven by prolonged warm periods, while sub-tropical regions show lower incidence due to cooler temperatures limiting mosquito survival. In con- trast, the third approach projects multiple irregular peaks, with transmission ceasing in winter across all regions. Simulations indicate that climatic events like heatwaves or flood- ing, can trigger mosquito population surges and malaria outbreaks, even in areas previously free of malaria, despite strong vector control efforts. However, the results demonstrate that sustained and effective vector control, particularly in regions with moderate temperatures, can substantially reduce malaria inci- dence. Effective malaria control requires incorporating weather predictions into intervention plans, and enhancing current vector control strategies with supple- mentary measures like larval source management. Accurate timing and targeting of these interventions, based on transmission season projections, are crucial for maintaining robust control as weather conditions evolve and to prepare for future challenges.