Anopheline Larval Habitats Seasonality and Species Distribution: A Prerequisite for Effective Targeted Larval Habitats Control Programmes

Abstract

BackgroundLarval control is of paramount importance in the reduction of malaria vector abundance and subsequent disease transmission reduction. Understanding larval habitat succession and its ecology in different land use managements and cropping systems can give an insight for effective larval source management practices. This study investigated larval habitat succession and ecological parameters which influence larval abundance in malaria epidemic prone areas of western Kenya.Methods and FindingsA total of 51 aquatic habitats positive for anopheline larvae were surveyed and visited once a week for a period of 85 weeks in succession. Habitats were selected and identified. Mosquito larval species, physico-chemical parameters, habitat size, grass cover, crop cycle and distance to nearest house were recorded. Polymerase chain reaction revealed that An. gambiae s.l was the most dominant vector species comprised of An.gambiae s.s (77.60%) and An.arabiensis (18.34%), the remaining 4.06% had no amplification by polymerase chain reaction. Physico-chemical parameters and habitat size significantly influenced abundance of An. gambiae s.s (P = 0.024) and An. arabiensis (P = 0.002) larvae. Further, larval species abundance was influenced by crop cycle (P≤0.001), grass cover (P≤0.001), while distance to nearest houses significantly influenced the abundance of mosquito species larvae (r = 0.920;P≤0.001). The number of predator species influenced mosquito larval abundance in different habitat types. Crop weeding significantly influenced with the abundance of An.gambiae s.l (P≤0.001) when preceded with fertilizer application. Significantly higher anopheline larval abundance was recorded in habitats in pasture compared to farmland (P = 0.002). When habitat stability and habitat types were considered, hoof print were the most productive followed by disused goldmines.ConclusionThese findings suggest that implementation of effective larval control programme should be targeted with larval habitats succession information when larval habitats are fewer and manageable. Crop cycles and distance from habitats to household should be considered as effective information in planning larval control.

Response of Anopheles gambiae s.l. (Diptera: Culicidae) to larval habitat age in western Kenya highlands

“…A recent study at the same site demonstrated that cropping cycle (land preparation, crop weeding and plant flowering) influenced larval abundance [23]. As the cropping cycle progresses at this study site, the farmers have a practice of not clearing the drainage ditches in their farms and small pools of stagnant water become suitable breeding habitats for malaria vectors.…”

Landscape Movements of Anopheles gambiae Malaria Vector Mosquitoes in Rural Gambia

“…In landscapes with extensive or widely scattered breeding sites, it will therefore be a considerable challenge to reduce mosquito numbers solely by larval control sufficiently to lower transmission and indeed this was the conclusion from such an attempt in central Gambia [23]. However, if breeding sites are localised, larval control within such a cordon sanitaire [58] may be a useful component of integrated malaria control [59]–[61]. Consideration of local geography and probability of An.gambiae dispersal into control areas is required to help inform such decisions.…”

Effect of Deforestation and Land Use Changes on Mosquito Productivity and Development in Western Kenya Highlands: Implication for Malaria Risk

“…In the current study, higher productivity of An. gambiae was associated with algae (23, 24). Our results are consistent with previous findings in lowland and highland areas in western Kenya in which occurrence of An.…”