Biology subjects

Yared, S.

Publications and source records attributed to Yared, S..

7 recordsLinked to original sources

bioRxiv2025

Genetic surveillance of Plasmodium-Anopheles compatibility markers during Anopheles stephensi associated malaria outbreak

Despite previous decline of malaria in Ethiopia, an outbreak in Dire Dawa in 2022 implicated invasive vector An. stephensi as responsible. The transmission of Plasmodium by invasive An. stephensi raises questions about the molecular basis of compatibility, and the origin of the Plasmodium being transmitted. The Plasmodium P47 gene is a parasite-vector interaction gene in Anopheles, and along with corresponding mosquito P47 receptor (P47Rec), can be critical in establishment of Plasmodium infections in anophelines. Here, we analyzed P47 and P47Rec sequences to determine the origin of Plasmodium detected in An. stephensi during the outbreak and evaluate markers of compatibility. Analysis of geographically informative SNPs in Pfs47 revealed that these P. falciparum exhibit the African haplotype. We also identified a single amino acid change in P47Rec within these An. stephensi, which could act as a marker for the propensity of An. stephensi populations to outbreaks. Together, we provide the basis for further study to deepen the understanding of invasive An. stephensi -African Plasmodium interactions to better control transmission of malaria and prevent further outbreaks.

evolutionary biology↗

bioRxiv2025

Anopheles stephensi larval habitat superproductivity and its relevance for larval source management in Africa

The invasion of Africa by Anopheles stephensi poses a significant threat to malaria elimination. As An. stephensi exploits a wide array of urban artificial larval habitats, it may be less impacted by rainfall variability compared to other native Anopheles species. We empirically investigated this assumption by quantifying the seasonal transition of an established population from eastern Ethiopia between rainy and dry periods. Monthly larval surveys generated evidence of significant heterogeneity between seasons in the type of habitat and their productivity. As the dry season progressed, An. stephensi productivity significantly concentrated in large water reservoirs (for drinking and construction) to a point in which up to 77% of all larvae originated from 23% of the sites. Such superproductive sites were primarily water cisterns used for residential or construction purposes. A two-patch metapopulation model of An. stephensi linked to rainfall data recreated the seasonal larval dynamics observed in the field and predicted that larval control targeted on superproducer water reservoirs, when implemented at coverages higher than 60%, may lead to An. stephensi elimination. Our findings highlight the role of environmental variability in regulating An. stephensi populations and open the window for the deployment of control strategies that exploit major mosquito population bottlenecks.

ecology↗

bioRxiv2024

Insecticide resistance and population structure of the invasive malaria vector, Anopheles stephensi, from Fiq, Ethiopia

Anopheles stephensi invasion in Ethiopia poses a risk of increased malaria disease burden in the region. Thus, understanding the insecticide resistance profile and population structure of the recently detected An. stephensi population in Fiq, Ethiopia, is critical to inform vector control to stop the spread of this invasive malaria species in the country. Following entomological surveillance for An. stephensi in Fiq, Somali region, Ethiopia, we confirmed the presence of An. stephensi morphologically and molecularly in Fiq. Characterization of larval habitats and insecticide susceptibility tests revealed that Fiq An. stephensi is most often found in artificial containers and is resistant to most adult insecticides tested (organophosphates, carbamates, pyrethroids) except for pirimiphos-methyl and PBO-pyrethroids. However, the immature larval stage was susceptible to temephos. Further comparative genomic analyses with previous An. stephensi populations from Ethiopia using 1,704 biallelic SNPs revealed genetic relatedness between Fiq An. stephensi and east-central Ethiopia An. stephensi populations, particularly Jigjiga An. stephensi. Our findings of the insecticide resistance profile, coupled with the likely source population of Fiq An. stephensi, can inform vector control strategies against this malaria vector in Fiq and Jigjiga to limit further spread out of these two locations to other parts of the country and continent.

evolutionary biology↗

bioRxiv2023

Building the vector in? Construction practices contribute to the invasion and persistence of Anopheles stephensi in Jigjiga, Ethiopia

Anopheles stephensi is a major vector of malaria in Asia and the Arabian Peninsula, and its recent invasion into Africa poses a significant threat to malaria control and elimination efforts on the continent. The mosquito is well-adapted to urban environments, and its presence in Africa could potentially lead to an increase in malaria transmission in cities. Most of the knowledge about An. stephensi ecology in Africa has been generated from studies conducted during the rainy season, when vectors are most abundant. Here, we provide evidence from the peak of the dry season in the city of Jigjiga, Ethiopia, and report the finding of An. stephensi immature stages infesting predominantly water reservoirs made to support construction operations (in construction sites or associated with brick manufacturing businesses). Political and economic changes in Ethiopia (and particularly the Somali Region) have fueled an unprecedented construction boom since 2018 that, in our opinion, has been instrumental in the establishment, persistence and propagation of An. stephensi via the year-round availability of perennial larval habitats associated with construction. We argue that larval source management during the dry season may provide a unique opportunity for focused control of An. stephensi in Jigjiga and similar areas.

ecology↗

bioRxiv2021

Tracking of Anopheles stephensi in Ethiopia using mitochondrial DNA reveals pattern of spread

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. The mode and history of introduction is important for predicting the likelihood of continued introduction and future spread. Analysis of An. stephensi genetic diversity and population structure can provide insight into the history of the mosquito in the HOA. We investigated genetic diversity of An. stephensi in eastern Ethiopia where detection suggests a range expansion to this region to understand the history of this invasive population. We sequenced the cytochrome oxidase subunit I (COI) and cytochrome B gene (CytB) in 187 An. stephensi collected from 10 sites in Ethiopia in 2018. Phylogenetic analyses using a maximum-likelihood approach and minimum spanning network were conducted for Ethiopian sequences. Molecular identification of bloodmeal sources was also performed using universal vertebrate CytB sequencing. Six COI-CytB haplotypes were observed based on five segregating sites, 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. In the phylogenetic and network analysis, we observed population differentiation based on the distribution of the haplotypes across the northeastern and central sites (Erer Gota, Dire Dawa, and Awash Sebat Kilo) compared to the southeastern sites and evidence of a South Asian origin of the HOA An. stephensi lineages. The presence of the putative South Asian haplotype of origin at sites closest to Ethiopias northeastern borders support route of introductions into Ethiopia from the northeast. Finally, molecular bloodmeal analysis revealed evidence of feeding on bovines, goats, dogs, and humans, as well as evidence of multiple (mixed) blood meals. In conclusion, we find support for the hypothesis for the recent expansion of An. stephensi into southeastern Ethiopia with multiple introductions. 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 potential for livestock movement to play a role in vector spread in this region.

ecology↗

bioRxiv2020

Comparison of the knockdown resistance locus (kdr) in Anopheles stephensi, An. arabiensis, and Culex pipiens s.l. suggests differing mechanisms of pyrethroid resistance in east Ethiopia

The malaria vector, Anopheles stephensi, which is typically restricted to South Asia and the Middle East, was recently detected in the Horn of Africa. Controlling the spread of this vector could involve integrated vector control that considers the status of insecticide resistance of multiple vector species in the region. Previous reports indicate that the knockdown resistance mutations (kdr) in the voltage-gated sodium channel (vgsc) are absent in both pyrethroid resistant and sensitive variants of An. stephensi in east Ethiopia but similar information on other vector species in the same areas is limited. In this study, kdr and the neighboring intron was analyzed in An. stephensi, An. arabiensis, and Culex pipiens s. l. collected in east Ethiopia between 2016 and 2017. Sequence analysis revealed that all of Cx. pipiens s.l. (n = 42) and 71.6% of the An. arabiensis (n=67) carried kdr L1014F known to confer target-site pyrethroid resistance. Intronic variation was only observed in An. stephensi (segregating sites = 6, haplotypes = 3) previously shown to have no kdr mutations. In addition, no evidence of non-neutral evolutionary processes was detected at the An. stephensi kdr intron which further supports target-site mechanism not being a major resistance mechanism in this An. stephensi population. Overall, these results suggest differences in evolved mechanisms of pyrethroid/DDT resistance in populations of vector species from the same region. Variation in insecticide resistance mechanisms in East Ethiopian mosquito vectors highlight possible species or population specific biological factors and distinct environmental exposures that shape their evolution.

evolutionary biology↗

bioRxiv2019

Geographical distribution of Anopheles stephensi in eastern Ethiopia

BackgroundThe recent detection of the South Asian malaria vector An. stephensi in Ethiopia and other regions in the Horn of Africa has raised concerns about its potential impact on malaria transmission. We report here findings of survey for this species in eastern Ethiopia using both morphological and molecular methods for species identification.\n\nMethodsAdult and larval/pupal collections were conducted at ten sites in eastern Ethiopia and Anopheles specimens species were determined using standard morphological keys and genetic analysis.\n\nResultsIn total, 2,231 morphologically identified An. stephensi were collected. A molecular approach incorporating both PCR endpoint assay and sequencing of portions of the internal transcribed spacer 2 (ITS2) and cytochrome oxidase I (COI) loci confirmed the identity of the An. stephensi in most cases (119/124 of the morphologically identified An. stephensi confirmed molecularly). Additionally, we observed Aedes aegypti larvae and pupae at many of the An. stephensi larval habitats.\n\nConclusionsOur findings show that An. stephensi is widely distributed in eastern Ethiopia and highlight the need for further surveillance in the southern, western and northern parts of the country and throughout the Horn of Africa.

ecology↗