Abstract
BackgroundThe recent detection of the South Asian malaria vector Anopheles stephensi in the Horn of Africa (HOA) raises concerns about the impact of this mosquito on malaria transmission in the region. Analysis of An. stephensi genetic diversity and population structure can provide insight into the history of the mosquito in the HOA to improve predictions of future spread. We investigated the genetic diversity of An. stephensi in eastern Ethiopia, where detection suggests a range expansion into this region, in order to understand the history of this invasive population.MethodsWe sequenced the cytochrome oxidase subunit I (COI) and cytochrome B gene (CytB) in 187 An. stephensi collected from 10 sites in Ethiopia in 2018. Population genetic, phylogenetic, and minimum spanning network analyses were conducted for Ethiopian sequences. Molecular identification of blood meal sources was also performed using universal vertebrate CytB sequencing.ResultsSix An. stephensi COI-CytB haplotypes were observed, with the highest number of haplotypes in the northeastern sites (Semera, Bati, and Gewana towns) relative to the southeastern sites (Kebridehar, Godey, and Degehabur) in eastern Ethiopia. We observed population differentiation, with the highest differentiation between the northeastern sites compared to central sites (Erer Gota, Dire Dawa, and Awash Sebat Kilo) and the southeastern sites. Phylogenetic and network analysis revealed that the HOA An. stephensi are more genetically similar to An. stephensi from southern Asia than from the Arabian Peninsula. Finally, molecular blood meal analysis revealed evidence of feeding on cows, goats, dogs, and humans, as well as evidence of multiple (mixed) blood meals.ConclusionWe show that An. stephensi is genetically diverse in Ethiopia and with evidence of geographical structure. Variation in the level of diversity supports the hypothesis for a more recent introduction of An. stephensi into southeastern Ethiopia relative to the northeastern region. We also find evidence that supports the hypothesis that HOA An. stephensi populations originate from South Asia rather than the Arabian Peninsula. The evidence of both zoophagic and anthropophagic feeding support the need for additional investigation into the potential for livestock movement to play a role in vector spread in this region.Graphical
Highlights
The recent detection of the South Asian malaria vector Anopheles stephensi in the Horn of Africa (HOA) raises concerns about the impact of this mosquito on malaria transmission in the region
In 2012, an urban malaria vector mosquito, Anopheles stephensi, which is common in South Asia, was detected in the HOA for the first time in Djibouti [9, 10], and in 2016 in eastern Ethiopia [11]
There is evidence that the HOA An. stephensi can transmit the local strains of P. falciparum and P. vivax in Djibouti [10] and Ethiopia [14], validating concern for the role An. stephensi may play in increasing malaria transmission
Summary
The recent detection of the South Asian malaria vector Anopheles stephensi in the Horn of Africa (HOA) raises concerns about the impact of this mosquito on malaria transmission in the region. In 2012, an urban malaria vector mosquito, Anopheles stephensi, which is common in South Asia, was detected in the HOA for the first time in Djibouti [9, 10], and in 2016 in eastern Ethiopia [11] This species range was believed to be limited to South Asia and the Middle East, including the eastern Arabian Peninsula [12]. There is evidence that the HOA An. stephensi can transmit the local strains of P. falciparum and P. vivax in Djibouti [10] and Ethiopia [14], validating concern for the role An. stephensi may play in increasing malaria transmission
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