Distribution and diversity of the vectors of Rift Valley fever along the livestock movement routes in the northeastern and coastal regions of Kenya.

Samwel O Arum,David P Tchouassi,Tobias Landmann,Christopher W Weldon,Benedict Orindi,Rosemary Sang,Hippolyte D Affognon

doi:10.1186/s13071-015-0907-1

Samwel O Arum, David P Tchouassi + Show 5 more

Open Access

https://doi.org/10.1186/s13071-015-0907-1

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Abstract

BackgroundKnowledge 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.MethodsMosquito 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.ResultsOver 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.ConclusionOur 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.

Highlights

Knowledge of vector ecology is important in understanding the transmission dynamics of vector borne disease
Abundance of primary and secondary vectors of Rift Valley fever (RVF) in diverse ecological zones and sites A total of 31,727 mosquitoes comprising 21 species belonging to 6 genera were captured from the 7 sampling sites (Table 1)
The highest number of mosquitoes was trapped in Mangai in ecological zone IV (n = 10,740) while the lowest occurred in Haney in ecological zone VI (n = 282)

Summary

Introduction

Knowledge of vector ecology is important in understanding the transmission dynamics of vector borne disease. 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. Rift Valley fever (RVF) is a viral disease that mainly affects livestock and humans, many other mammalian species have been shown to be susceptible [1,2,3]. The infected eggs can enter diapause in dry dambos for long periods and hatch into infectious mosquitoes during periods of extended rainfall This may result in transmission of the virus to nearby animals and human beings when the vectors seek blood meals. Once primary transmission of the virus has taken place, secondary vectors belonging to the genera Culex, Anopheles and Mansonia, which take over flooded grounds for breeding, contribute to the amplification of the virus due to their ubiquitous biting patterns, resulting in outbreaks [4, 15,16,17]

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