Simulation of hydrology and population dynamics of Anopheles mosquitoes around the Koka Reservoir in Ethiopia

Abstract

This thesis applies the HYDRology, Entomology and MAlaria Transmission Simulator (HYDREMATS) to the environment around a water resources reservoir in Ethiopia. HYDREMATS was modified to simulate the local hydrology and the mosquito population dynamics influenced by the reservoir system. The hydrology component of HYDREMATS including a representation of the groundwater was coupled with a reservoir model to describe the spatiotemporal variability of the groundwater table, and the variability in shoreline locations. The entomology component was modified to match the relatively humid environment. HYDREMATS was applied to two villages around the Koka Reservoir in Ethiopia, one adjacent to the reservoir, Ejersa, and the other located 12 km away from it, Gudedo. Meteorological data were collected from July 2011 to February 2013. Entomological data collection started in July 2012 and continued until February 2013. Adult mosquitoes were sampled from the two field sites and classified at the genus level, i.e., Anopheles or Culex. Because of their geographical proximity, the climatology in Ejersa and the climatology in Gudedo were comparable; however, entomological conditions in the two villages were distinct. Ejersa experienced an enhanced and prolonged mosquito season. HYDREMATS was able to simulate the hydrology and the population dynamics of Anopheles mosquitoes at both sites for the period, from January 2012 to February 2013. The model applied to Ejersa simulated a large mosquito population and a prolonged mosquito breeding season because of the existence of the reservoir, in agreement with observations. Especially, a large mosquito population in the post-rainy season was sustained in the simulation due to a large shoreline breeding area. The model applied to Gudedo simulated smaller mosquito population, but it failed to reproduce observed adult mosquito population dynamics correctly. However, the simulated adult mosquito population dynamics in Gudedo resembled those of the observed larvae samples. Further model calibration and validation will be conducted as more data become available. This study demonstrates that HYDREMATS can serve as an effective tool to simulate local hydrology and mosquito population dynamics at a reservoir environment, given hydrological and entomological parameters specified for the given field site.