The role of Agricultural Chemicals on Malaria Vectors’ Fitness in a Rice Agro-Ecosystem in Kenya

Abstract

Control of African malaria vectors continue to depend on insecticides through Indoor residual sprays or Insecticide treated nets but insecticide-resistance is a hindrance to its excellence. An improved knowledge of mosquito ecology could inform better vector control measures. This study intended to establish any negative effects of agrochemicals on malaria vector ‘fitness’ in rice agro ecosystems in Mwea irrigation scheme. Four agro-chemicals in paddy and simulated field experiments were evaluated for their effects on vector ‘fitness’. Pupae were sampled in agro-chemical exposed paddies and mosquito eggs incubated in simulated conditions of different agrochemical combinations. Vector ‘fitness’ was defined as longevity and size of emergent Anopheles mosquitoes. The mean longevity of agrochemical exposed Anopheles mosquitoes was 6.5 days in the paddy experiment and 7.1 days in the simulated experiments. Respective controls had a mean life span of 18 days in the paddy and 15 days for simulated experiment. Comparison for differences in these life spans on paired t- tests gave statistically significant results (P = 0.003) for the paddy trial, and for simulated experiment (P =.000). These results were taken to suggests that agrochemical exposed mosquitoes suffer reduced longevity compared to their non agrochemical exposed controls in both trials. This finding could indicate that agrochemicals can be a passive integrated vector control tool.

Keywords: Agrochemicals, Longevity, Size, Anopheles Spp