Influence of climate on malaria transmission depends on daily temperature variation

TLDR

Malaria transmission is strongly influenced by environmental temperature, yet most studies rely on mean temperatures and extrapolate from unrealistic laboratory conditions, leaving biological drivers poorly quantified. The study aims to demonstrate that daily temperature fluctuations influence parasite infection, development rates, and mosquito biology, and to show that incorporating these effects into predictive models is essential for optimizing control and adaptation strategies under future climates. The authors use empirical data to show that daily temperature fluctuations affect parasite infection, development rates, and key mosquito biological traits that determine malaria transmission intensity. The study finds that temperature fluctuations accelerate processes at low mean temperatures but slow them at high means, and that at transmission extremes fluctuations enable transmission at lower means while potentially blocking it at higher means.

Abstract

Malaria transmission is strongly influenced by environmental temperature, but the biological drivers remain poorly quantified. Most studies analyzing malaria–temperature relations, including those investigating malaria risk and the possible impacts of climate change, are based solely on mean temperatures and extrapolate from functions determined under unrealistic laboratory conditions. Here, we present empirical evidence to show that, in addition to mean temperatures, daily fluctuations in temperature affect parasite infection, the rate of parasite development, and the essential elements of mosquito biology that combine to determine malaria transmission intensity. In general, we find that, compared with rates at equivalent constant mean temperatures, temperature fluctuation around low mean temperatures acts to speed up rate processes, whereas fluctuation around high mean temperatures acts to slow processes down. At the extremes (conditions representative of the fringes of malaria transmission, where range expansions or contractions will occur), fluctuation makes transmission possible at lower mean temperatures than currently predicted and can potentially block transmission at higher mean temperatures. If we are to optimize control efforts and develop appropriate adaptation or mitigation strategies for future climates, we need to incorporate into predictive models the effects of daily temperature variation and how that variation is altered by climate change.