Mosquito larval habitats in a semiarid ecosystem in Eritrea: impact of larval habitat management on Anopheles arabiensis population.

This study investigated the impact of larval management and the temporal variation in larval productivity in Eritrea, a semiarid ecosystem. Results of this study show that mosquito breeding persists throughout the year mainly in stream bed pools. Anopheles arabiensis production in the ephemeral natural aquatic habitats such the streambed pools was high throughout the year and negatively associated with rainfall (r = -0.288, P = 0.047). High densities of An. arabiensis larvae were also recorded from canals and drainage channels at wells and communal water supply points. The numerous water supply locations and wells help sustain malaria transmission by serving as sources of anophelines where people aggregate. There was a strong association between larval production and adult emergent densities (r = 0.365, P = 0.011). The results of this study further show that implementation of larval control strategies in the study villages significantly reduced vector productivity as measured by both larval (F = 24.919, df = 1,178, P < 0.001) and adult An. arabiensis densities (F = 3.052, df = 1,119, P = 0.014) in the treated sites over the 24-month study period. The results of this semiarid larval management model suggests that 1) larval management backed by habitat identification, mapping, and surveillance is a feasible tactic for managing malaria vectors, 2) a special focus in such semiarid ecosystems should be targeted to the highly productive larval habitats along stream beds and others of periodic importance derived from human activities, and 3) public information and sensitization of communities to participate in controlling the pre-adult stages of anopheline mosquitoes is central for success.