Ecological succession and its impact on malaria vectors and their predators in borrow pits in western Ethiopia

Abstract

Soil pits excavated for home construction are important larval habitats for malaria vectors in certain parts of Africa. Borrow pits in diverse stages of ecological succession in a maize-farming region of Western Ethiopia were surveyed to assess the relationships between stage of succession and the structure and composition of invertebrate and plant communities, with particular attention to Anopheles gambiae s.l. and An. coustani, the primary local malaria vectors. An array of 82 borrow pits was identified in a multi-lobed drainage basin in the community of Woktola. Each pit was evaluated on its physical features and by faunal and floral surveys during August, 2011, at the height of the longer rainy season (kiremt). Anopheles gambiae s.l. and An. coustani were the sole immature anophelines collected, often coexisting with Culex spp. Sedges were the most common plants within these pits, and included Cyperus elegantulus, C. flavescens, C. erectus and C. assimilis. The legume Smithia abyssinica, Nile grass (Acroceras macrum), cutgrass (Leersia hexandra), clover (Trifolium spp.), and the edible herb Centella asiatica, were also common in these habitats. No plant species in particular was strongly and consistently predictive of the presence or absence of mosquito immatures, particularly with regard to An. coustani.

Larval habitats of Anopheles gambiae senso lato (Diptera-Culicidae) in Anger Gute resettlement villages, western Ethiopia

“…The negative effect of vegetation cover on the mosquito larval abundance is consistent with prior observations in Ethiopia [16,31,32,34] and elsewhere in Africa [34,37]. The works of [34,37] evident that deforestation and cultivation of natural swamps created conditions favorable for An.…”

“…breeds in sunlit rain water pools that were free of vegetation during the wet season [31,32] and in residual pools along drainage systems in dry season [16,19,22,23]. The mosquito larvae preferred vegetation free rain pools that were located along footways and roads than elsewhere in the study setting due to the influence of fast growing standing vegetation and associated fauna that might act as larval predators [32,33] However, in dry season, mosquito breeding sites are limited to drainage areas such as streams, rivers and lakes due to lack of rain water and the impact of desiccation. But after onset of rain, the streams will increase and most larval habitats located along streams will be submerged by overflow of the stream water and succession of flora and fauna in the drainage areas [23,32].…”

Geographically extensive larval surveys reveal an unexpected scarcity of primary vector mosquitoes in a region of persistent malaria transmission in western Zambia

“…Signi cantly higher abundance in permanently waterlogged dambo habitats across both seasons re ects the recognised preference of An. coustani s.s. for more established water bodies [57]. The species displays a preference for natural vegetated water bodies and an aversion to temporary, non-vegetated pools elsewhere [58], and this is supported by its ubiquitous presence in vegetated habitats [19] across Barotseland in this study.…”

Differential contribution of Anopheles coustani and Anopheles arabiensis to the transmission of Plasmodium falciparum and Plasmodium vivax in two neighbouring villages of Madagascar

“…to An. coustani in breeding sites by increasing vegetation cover, was also demonstrated for borrow pits in Ethiopia [33]. Through the analysis of the Anopheles vector feeding behaviour, only An.…”