Abstract:
BACKGROUND : Knowledge of vector ecology is important in understanding the transmission dynamics of vector
borne disease. In this study, we determined the distribution and diversity of mosquitoes along the major nomadic
livestock movement routes (LMR) in the traditional pastoral ecozone of northeastern Kenya. We focused on the
vectors of Rift Valley fever virus (RVFv) with the aim of understanding their ecology and how they can potentially
influence the circulation of RVFv.
METHODS : Mosquito surveys were conducted during the short and long rainy seasons from November 2012 to
August 2014 using CO2-baited CDC light traps at seven sites selected for their proximity to stopover points that
provide pasture, water and night bomas (where animals spend nights). We compared mosquito abundance and
diversity across the sites, which were located in three ecological zones (IV, V and VI), based on the classification
system of agro-ecological zones in Kenya.
RESULTS : Over 31,000 mosquitoes were trapped comprising 21 species belonging to 6 genera. Overall mosquito
abundance varied significantly by ecological zones and sites. Mansonia species (Ma. uniformis and Ma. africana)
were predominant (n = 12,181, 38.3 %). This was followed by the primary RVF vectors, Ae. ochraceus and Ae.
mcintoshi comprising 17.9 and 14.98 %, respectively, of the total captures and represented across all sites and
ecological zones. The Shannon diversity index ranged from 0.8 to 2.4 with significant zone, site and seasonal
variations. There was also significant species richness of RVF vector across ecological zones.
CONCLUSION : Our findings highlight differential occurrence of RVFv vectors across ecological zones and sampling
sites, which may be important in determining areas at risk of emergence and circulation of RVFv. Moreover, the
vector distribution map along LMR generated in this study will guide potential interventions for control of the
disease, including strategic vaccination for livestock.
