The effect of climate on the distribution of the dengue fever vector, Aedes aegypti, in Ecuador

Background/Question/Methods

Climate change is projected to increase the prevalence of mosquito-borne disease epidemics by expanding the geographic range of mosquitoes.  Dengue fever (DF), a virus transmitted to humans by the Aedes aegypti mosquito, is one of the most significant and rapidly spreading vector-borne viruses.  With no vaccine currently available, an estimated 2.5 billion people in over 100 countries are at risk for DF, yet few studies have empirically modeled the effect of climate on the distribution of A. aegypti on a fine scale.  The objective of this research was to develop a climate-driven, geographical model of the distribution of A. aegypti in Ecuador to test the hypothesis that projected changes in climate will increase the potential range of the mosquito.  Using GIS, raster grids of climate (1x1 km) were developed from meteorological data from over 100 weather stations provided by the National Meteorological and Hydrological Institute of Ecuador (1982–2005).  The historical presence or absence of A. aegypti was mapped based on quarterly entomological surveys provided by the Ecuadorian Ministry of Health (2000 – 2005).  Using FORTRAN, I determined the optimal climatic gradient space of A. aegypti in Ecuador by estimating the relative and absolute abundance of the mosquito along dual temperature and precipitation gradients. 

Results/Conclusions

Preliminary results indicated that A. aegypti distribution in Ecuador was limited by temperature more than by precipitation. A. aegypti was found predominantly in the hottest regions (mean temperature >25^○C), but was distributed across a wide range of precipitation.  The future distribution of A. aegypti in Ecuador will be projected using the A2 and B2 climate change scenarios from ECHAM4 and HADAM3 in the PRECIS regional climate simulation model (25 x 25 km).  This critical research will aid in the development of a geographical model of disease transmission that will allow public health policy makers to anticipate and mitigate future DF epidemics. Since DF is transmitted primarily by one mosquito species, the methods and results of this analysis will be globally relevant.