VECTOR BIOLOGY AND GENOMICS OF ANOPHELES IN SOUTHERN AND CENTRAL AFRICA
Embargo until
2021-05-01
Date
2018-12-18
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Publisher
Johns Hopkins University
Abstract
Nchelenge District in Zambia has high malaria transmission despite intensive malaria control. The primary mosquito species contributing to transmission is Anopheles funestus s.s., a species for which genetic and genomic data is lacking compared to other important vectors. To investigate the population dynamics of An. funestus that contribute to transmission and to eventually prepare a suitable set of genetic markers for future study, it was necessary to improve the existing baseline of genomic information. 43 field specimens of An. funestus were gathered from sites in central and southern Africa. Illumina shotgun sequencing was conducted and the first 43 complete high-quality An. funestus complete mitogenomes were assembled. The full-length mitogenome yielded a set of 567 polymorphic sites from which population genetics markers may be developed. Analyses conducted on the full set of 43 mitogenomes from three countries illuminated phylogenetic relationships and a complex demographic history.
To investigate outdoor transmission in Nchelenge, which may partially explain the refractoriness of transmission to standard indoor-based malaria interventions, Centers for Disease Control light traps (CDC LTs) were set outdoors in August of 2016. The anophelines collected were more diverse than seen from primarily indoor collections in Nchelenge. Sequencing, phylogenetics, and morphology revealed more than 12 phylogenetic groups of anophelines, some of which appear to be competent for malaria parasites. Approximately 1% of outdoor-collected An. funestus were parasite-positive, which calls for further investigation of the involvement of these vectors in outdoor transmission.
The outdoor CDC LTs were set with three different schemes, including traps baited with a synthetic human odorant blend (BG-LureĀ®). Models indicated that the neither the abundance nor the species diversity of female anophelines differed between traps placed outdoors near humans, animals or baited with synthetic attractant. Instead, for both the number of anophelines caught per trap as well as the number of species present in a trap, the best predictors were site (whether traps were lakeside or inland) and the numbers of people sleeping under or without bednets. Together, these studies represent significant steps forward in understanding the entomological drivers of malaria transmission in Nchelenge.
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Keywords
vector biology, malaria