Tropical Malaria Does Not Mean Hot Environments

Abstract

If global warming progresses, many consider that malaria in presently malaria-endemic areas will become more serious, with increasing development rates of the vector mosquito and malaria parasites. However, the correlation coefficients between the monthly malaria cases and the monthly mean of daily maximum temperature were negative, showing that the number of malaria cases in tropical areas of Africa decreases during the season when temperature was higher than normal. Moreover, an analysis of temperature and development rate using a thermodynamic model showed that the estimated intrinsic optimum temperatures for the development of the malaria parasites, Plasmodium falciparum and P. vivax, in the adult mosquito stage and that of the vector mosquito Anopheles gambiae s.s. were all approximately 23-24 degrees C. Here, the intrinsic optimum temperature is defined in the thermodynamic model as the temperature at which it is assumed that there are no or negligible adverse effects for development. Therefore, this study indicates that the development of malaria parasites in their mosquito hosts and the development of their vector mosquitoes are inhibited at temperatures higher than 23-24 degrees C. If global warming progresses further, the present center of malarial endemicity in sub-Saharan Africa will move to an area with an optimum temperature for both the vector and the parasite, migrating to avoid the hot environment.

Malaria ecology and climate change

“…• C in the case of P. vivax [13]. Additionally, while high temperatures speed up mosquito development and increase frequency of blood feeding, they also reduce mosquito survival [14], further introducing complexity into the relationship between temperature and malaria transmission.…”

“…The Malaria Ecology Index could thus be constructed using the following equation for development rate r to completion of sporogony, calibrated from observated data in the literature [13]: r = 0.06044 Results presented below are all robust to using this other version of the index, likely because mean monthly temperatures at national level rarely reach those upper temperature thresholds for Plasmodium physiology.…”

“…The maps shows percentage growth rates of the Malaria Ecology Index in places with nonzero index values before 2010. The top map uses the basic MEI equation, and the bottom map constructs the MEI using the sporogony function that incorporates the adverse effects of high temperatures on parasite development [13]. The growth rates are positive in nearly the entire world, emphasizing the pernicious effect that climate change will have on the ecology of malaria.…”

Development and reproduction of five Tetranychus species (Acari: Tetranychidae): Do they all have the potential to become major pests?

“…The non-linear thermodynamics model describes the developmental rate over a wider range of temperatures and allows for estimating the optimum temperatures for development. The equation of the non-linear thermodynamics [Sharpe-Schoolfield-Ikemoto (SSI)] model can be expressed as follows (Ikemoto 2005(Ikemoto , 2008Shi et al 2011): (Ikemoto 2005) and it is expressed as follows:…”

Temperature-dependent development and reproductive traits of Tetranychus macfarlanei (Acari: Tetranychidae)

“…On the other hand, the non-linear thermodynamics model describes the developmental rate over a wide range of temperatures and estimates of optimum temperatures for development. The equation of the non-linear thermodynamics (Sharpe-Schoolfield-Ikemoto [SSI]) model can be expressed as follows (Ikemoto 2005(Ikemoto , 2008Shi et al 2011):…”