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 the development of new vector control tools. However, the factors that guide the aquatic habitat selection of gravid females are poorly understood. The present study explored the relative attractiveness of similar artificial ponds (0.8 m ) aged at varying lengths prior to opening in such a way that wild Anopheles arabiensis could choose between ponds that were freshly set up, or were aged 4 or 17 days old, to lay eggs. Physicochemical parameters, bacterial profile and volatile organic compounds emitted from ponds were investigated over three 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 a significantly higher turbidity combined with higher water temperature, higher nitrite levels and a lower pH and chlorophyll level than the older ponds. Round by round analyses suggested that bacteria communities differed between age groups and also that 4-heptanone, 2-ethylhexanal and an isomer of octenal were exclusively detected from the fresh ponds. These characteristics may be useful with respect to developing attract and kill strategies for malaria vector control.

Controlling mosquitoes with semiochemicals: a review

“…A nonanoic acid (16%), tetradecanoic acid (83%) and methyl tetradecanoate (1%) blend was found to stimulate oviposition, whereas hexadecenoic acid methyl ester deterred oviposition [53]. The importance of bacterial profiles in combination with physiochemical properties and semiochemicals for oviposition site selections was demonstrated by Eneh et al [54] in a study showing that on average twice as many An. arabiensis instar larvae were found in freshwater ponds when compared to aged ponds (4-days-old).…”

Using sibship reconstructions to understand the relationship between larval habitat productivity and oviposition behaviour in Kenyan Anopheles arabiensis

“…However, the uptake of this intervention is impeded by the management effort required [10] and the lack of knowledge of aquatic habitats that are the most preferred for egg laying, which would allow a more spatially-targeted approach. The oviposition behaviour of Anopheles mosquitoes, and specifically the preference of particular aquatic habitats for egg-laying, has been studied in order to better target LSM and to develop novel attract and kill strategies for vector control [11, 12]. Habitat preferences are frequently inferred from the abundance of early instar larvae in a habitat [13].…”

“…Habitat preferences are frequently inferred from the abundance of early instar larvae in a habitat [13]. This relies on the assumption that higher early instar larval density results from a greater number of gravid females selecting the site for oviposition [11, 12]. However, to date only indirect tests of this assumption exists [14].…”

Testing a pyriproxyfen auto-dissemination station attractive to gravid Anopheles gambiae sensu stricto for the development of novel attract-and-kill strategies for malaria vector control

“…Gravid females were released inside an experimental hut and assuming a random dispersal out through the open eaves, it is reasonable to assume, that a proportion of gravid females leaving the hut through the eave facing away from the bait-station went straight to the next open pond to lay eggs. To efficiently use a limited number of bait-stations in the natural field environment that is characterized with numerous aquatic habitats (18,22), the attractiveness of bait-stations might be improved through innovative release technologies and formulation of more attractive chemical blends (47,(49)(50)(51).…”