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Unformatted text preview: F ORUM Tropical Malaria Does Not Mean Hot Environments TAKAYA IKEMOTO 1 Department of Microbiology, Teikyo University School of Medicine, Tokyo 173-8605, Japan J. Med. Entomol. 45(6): 963Ð969 (2008) 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 coefÞcients 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 ' 23Ð24 8 C. Here, the intrinsic optimum temperature is deÞned 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 23Ð24 8 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. KEY WORDS Anopheles gambiae , Plasmodium falciparum , intrinsic optimum temperature, Africa, malaria Global warming is a serious problem considering its consequences, such as a rise in the incidence and spread of diseases like malaria. As global warming progresses, there is concern for increased transmission of some tropical diseases and potential for their ex- pansion into temperate regions (Sutherst 1993). Moreover, many consider that malaria in presently malaria-endemic areas will become more serious with increasing developmental rates of vector mosquitoes and malaria parasites (Lindsay and Birley 1996, Massad and Forattini 1998, Craig et al. 1999, Pascual et al. 2006). These predictions are mostly based on the change of global temperature and the present distri- bution of malaria parasites and their vector mosqui- toes. Predictive studies based on biological responses of parasites and vector to warming are rarely per- formed. Here, I attempt to analyze the correlation between the seasonal number of malaria cases in some districts of tropical Africa and the seasonal ßuctuation of tem- perature there. Moreover, the intrinsic optimum tem- peratures (T F ) for the development of the malaria parasites and the vector mosquito are estimated by using a thermodynamic model, which is able to exhibit the minimum effects on enzyme inactivation in rela- tion to development of ectotherms at low and high...
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- Fall '10
- Parasitology, intrinsic optimum temperature