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

BACKGROUND & OBJECTIVES The study was undertaken to characterize factors influencing differential productivity of 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 were identified 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 an Orion pH/conductivity meter. Turbidity was measured using a Hach 2100A turbidity meter. Algal count density was 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%) were Anopheles 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 density and 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 that anti-larval source reduction measures aimed at manipulating physicochemical variables in larval habitats to eliminate larval production have a chance of succeeding in an integrated vector control program.