Factors influencing differential larval habitat productivity of Anopheles gambiae complex mosquitoes in a western Kenyan village

Abstract

Background & objectives: The study was undertaken to characterize factors influencing differential productivityof Anopheles gambiae complex mosquitoes at larval habitats in a rural village in western Kenya.Methods: Longitudinal larval sampling was done using an area sampler for 3 months. Emerged adults wereidentified to species level morphologically using taxonomic keys and to sub-species by polymerase chain reaction(PCR). Nutrient content was analyzed using persulphate oxidation method. Water pH was measured using anOrion pH/conductivity meter. Turbidity was measured using a Hach 2100A turbidity meter. Algal count densitywas estimated using a sedge-wick rafter cell.Results: A total 3367 larvae were harvested. Out of 500 adults subjected to PCR analysis 358 (71.6%) wereAnopheles gambiae s.s., 127 (25.4%) An. arabiensis while PCR amplification failed for 15 (3%) specimens.Rainwater pools were the most productive habitat type. There was a positive association between algal densityand larval density (p<0). Total nitrogen, water pH and turbidity were positively correlated with larval density(p<0.01) and pH was negatively associated with larval density.Conclusion: Results indicate water nutrient and algal content in larval habitats of An. gambiae play crucial,dual roles in the resource ecology of these mosquitoes. Overall, the findings of this study support the notion thatanti-larval source reduction measures aimed at manipulating physicochemical variables in larval habitats toeliminate larval production have a chance of succeeding in an integrated vector control program.

Keywords

• Anopheles gambiae
• larval productivity
• nutrients
• rainwater pools