The potential for environmental management to contribute to malaria vector control in western Niger

Abstract

This thesis investigated the potential for environmental management techniques to contribute to malaria vector control in Niger, with a case study on Banizoumbou village in western Niger. Numerical modeling was used to simulate habitat modifications in the form of leveling a topographic depression, ploughing the land surface to enhance infiltration and providing barriers to surface runoff on hillslopes. The hydrologic model described by Bomblies et al. (2008) was used for the modeling investigation, calibrated using environmental observations obtained in Banizoumbou for the years 2005, 2006 and 2007. The modeling investigation showed that leveling of topographic depressions could reduce the persistence time of a pool to less than the time needed for establishment of mosquito breeding, approximately 7 days. Increasing the surface soil permeability by ploughing also reduced the persistence time of the pool but was not as effective as leveling. Therefore leveling is the recommended intervention for pools of a small to intermediate size, while ploughing would be recommended for large pools where leveling would require too much work to implement. Interception of hillslope runoff using a barrier was demonstrated to be the most effective way to prevent a pool from becoming breeding habitat. However, this method has the most risk of creating unintended downstream impacts and therefore must be used with extreme caution. A field trial was also undertaken during July to September 2007 in Banizoumbou to investigate the efficacy of neem seeds as a larvicide and to reduce adult emergence from breeding pools.

(cont.) The neem field trial showed that twice-weekly applications of neem seed powder to known breeding habitats of Anopheles larvae in 2007 resulted in 49% fewer adult female Anopheles gambiae s.L mosquitoes in Banizoumbou compared with previous captures under similar environmental conditions and with similar habitat characteristics in 2005 and 2006. The results of the neem field trial suggest that neem seeds could provide an appropriate, sustainable larvicide for the malaria vector An. gambiae s.I. in the Sahel region of Niger and adjacent areas having similar environmental characteristics and vector dynamics.