Temporal distribution and spatial pattern of abundance of the Rift Valley fever and West Nile fever vectors in Barkedji, Senegal

Abstract

The temporal distribution and spatial pattern of abundance of mosquito vectors of Rift Valley fever (RVf) and West Nile fever (WNf) were studied during the 2005 and 2006 rainy seasons at Barkedji, Senegal. Mosquitoes were collected every two weeks with CDC light traps with dry ice at 79 sites including temporary ponds, barren, shrubby savannah, wooded savannah, steppes, and villages at different distances (between 0 and 600 m) from the nearest pond. The temporal distributions of these vectors varied between 2005 and 2006 and were positively correlated with rainfall for Aedes (Aedimorphus) vexans Patton, with rainfall after a lag time of one month for Culex (Culex) poicilipes (Theobald) and Culex (Culex) neavei Theobald. All the vectors had their highest abundances and parity rates between September and November. The highest vector abundances were observed in the barren and temporary ponds. The distance of trap location to the nearest ponds was negatively correlated to the abundance of the vectors. Taking into account the linear regression equations, it was predicted that mosquitoes would not disperse and be collected by the light trap, up to 1,500 m to the nearest ponds. The implications of these findings in the epidemiology and control of RVF and WNF at Barkedji are discussed.