Anopheles arabiensis oviposition site selection in response to habitat persistence and associated physicochemical parameters, bacteria and volatile profiles.

Abstract

A better understanding of the oviposition behaviour of malaria vectors might facilitate development of new vector control tools. However, factors that guide aquatic habitat selection of gravid females is poorly understood. This study explored the relative attractiveness of similar artificial ponds (0.8 m2 ) aged at varying length prior to opening in such a way that wild Anopheles arabiensis could choose between ponds that were freshly set up, 4 or 17 days old to lay eggs. Physicochemical parameters, bacterial profile and volatile organic compounds emitted from ponds were investigated over 3 experimental rounds. Fresh ponds contained on average twice as many An. arabiensis instar larvae (mean: 50, 95% confidence interval (CI): 29–85) as the ponds that had aged 4 days (mean: 24, 95% CI: 14–42) and 17 days (mean: 20, 95% CI: 12–34). Fresh ponds were associated with significantly higher turbidity combined with higher water temperature, higher nitrite levels and lower pH and chlorophyll level than the older ponds. Round by round analyses suggested that bacteria communities differed between age groups and 4-heptanone, 2-ethylhexanal and an isomer of octenal, were exclusively detected from the fresh ponds. These characteristics may be useful for developing attract and kill strategies for malaria vector control.