Hydrological and climatological determinants of African anopheline habitat
Within the semi-arid Sahel zone of Africa, serious malaria epidemics arise as a result of the annual wet season. We are studying the environmental determinants of malaria outbreak occurrence in this region with the aid of numerical modeling techniques. We are involved in an inter-disciplinary study to investigate the dependence of mosquito breeding and infection rates on factors such as surface water pooling which is the result of various hydroclimatological variables. In a unique approach, individual mosquitoes in a small study area in Niger will be modeled numerically in a simulation coupled with a small-scale hydrology model. Model input will include satellite-acquired remotely sensed data for vegetation, soil moisture and topography. With results validated by field investigations, variation in mosquito abundance and infection rates will be simulated. This numerical modeling tool will shed light on dynamics of outbreak occurrence and will help the targeting of intervention efforts.
The figure below shows three years of weekly malaria prevalence data. This is data obtained from the Niger ministry of health, and spans the entire country. Superimposed on this curve is GPCP average monthly precipitation data for the period 1979-2004, showing the strong response of malaria cases to the mosquito population explosion that inevitably follows extended pool persistence which mosquitoes use to breed. The peak of the malaria prevalence coincides with the end of the rainy season, most likely because mosquito populations can continue to grow up to this point.