Insecticide resistance in Anopheles stephensi in Somali Region, eastern Ethiopia

Yared, Solomon; Gebressielasie, Araya; Damodaran, Lambodhar; Bonnell, Victoria; López, Karen; Janies, Daniel; Carter, Tamar E.

doi:10.1186/s12936-020-03252-2

Cited by 63 publications

(53 citation statements)

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“…Widespread pyrethroid resistance in An. stephensi has been reported from Asia [ 19 ] and resistance has also been reported in Ethiopia [ 20 ]. However, to combat and control this invasive vector, a fuller understanding of insecticide resistance profiles is necessary.…”

Section: Discussionmentioning

confidence: 99%

An update on the distribution, bionomics, and insecticide susceptibility of Anopheles stephensi in Ethiopia, 2018–2020

Balkew¹,

Mumba²,

Yohannes³

et al. 2021

Malar J

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Background Anopheles stephensi, an invasive malaria vector, was first detected in Africa nearly 10 years ago. After the initial finding in Djibouti, it has subsequently been found in Ethiopia, Sudan and Somalia. To better inform policies and vector control decisions, it is important to understand the distribution, bionomics, insecticide susceptibility, and transmission potential of An. stephensi. These aspects were studied as part of routine entomological monitoring in Ethiopia between 2018 and 2020. Methods Adult mosquitoes were collected using human landing collections, pyrethrum spray catches, CDC light traps, animal-baited tent traps, resting boxes, and manual aspiration from animal shelters. Larvae were collected using hand-held dippers. The source of blood in blood-fed mosquitoes and the presence of sporozoites was assessed through enzyme-linked immunosorbent assays (ELISA). Insecticide susceptibility was assessed for pyrethroids, organophosphates and carbamates. Results Adult An. stephensi were collected with aspiration, black resting boxes, and animal-baited traps collecting the highest numbers of mosquitoes. Although sampling efforts were geographically widespread, An. stephensi larvae were collected in urban and rural sites in eastern Ethiopia, but An. stephensi larvae were not found in western Ethiopian sites. Blood-meal analysis revealed a high proportion of blood meals that were taken from goats, and only a small proportion from humans. Plasmodium vivax was detected in wild-collected An. stephensi. High levels of insecticide resistance were detected to pyrethroids, carbamates and organophosphates. Pre-exposure to piperonyl butoxide increased susceptibility to pyrethroids. Larvae were found to be susceptible to temephos. Conclusions Understanding the bionomics, insecticide susceptibility and distribution of An. stephensi will improve the quality of a national response in Ethiopia and provide additional information on populations of this invasive species in Africa. Further work is needed to understand the role that An. stephensi will have in Plasmodium transmission and malaria case incidence. While additional data are being collected, national programmes can use the available data to formulate and operationalize national strategies against the threat of An. stephensi.

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Section: Discussionmentioning

confidence: 99%

An update on the distribution, bionomics, and insecticide susceptibility of Anopheles stephensi in Ethiopia, 2018–2020

Balkew¹,

Mumba²,

Yohannes³

et al. 2021

Malar J

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“…stephensi mosquito distribution into major cities in Africa, where large malaria outbreaks could occur among growing resident populations susceptible to the disease ( 14 ). Furthermore, a high level of resistance among mosquitoes to all insecticide families (e.g., organochlorates, pyrethroids, carbamates, and organophosphates) has been described in Djibouti and Ethiopia ( 8 , 15 ). In semiarid regions such as the Republic of Djibouti, residents often store water in plastic drums that act as breeding sites for An.…”

Section: Discussionmentioning

confidence: 99%

Role of Anopheles stephensi Mosquitoes in Malaria Outbreak, Djibouti, 2019

Santi¹,

Khaireh²,

Chiniard³

et al. 2021

Emerg. Infect. Dis.

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T he Republic of Djibouti, bordered by Eritrea, Ethiopia, and Somalia, is a semiarid country in the Horn of Africa. The population comprises <900,000 persons, 70% of whom live in Djibouti, the capital city. Before 2013, malaria was hypoendemic to the country, with low levels of transmission in periruban and rural areas during December-May. Localized outbreaks occurred regularly, possibly caused by migration from surrounding countries. Most cases were caused by infection with Plasmodium falciparum (>80%) or P. vivax. Before 2013, researchers considered the Anopheles arabiensis mosquito to be the primary vector (1).The incidence of malaria had drastically decreased in the country since 2008; by 2012, this transmission level was compatible with preelimination goals (2,3). In 2013, an autochthonous outbreak of malaria occurred in Djibouti; fi eld entomologic investigations identifi ed An. stephensi mosquitoes as a new malaria vector (4). This species, a known vector of urban malaria in India and the Arabian Peninsula, has changed the epidemiologic profi le of malaria in Djibouti (5). In 2018, malaria incidence increased to 25,319 confi rmed cases (64% caused by P. falciparum and 36% by P. vivax) and >100,000 suspected cases (Appendix Figure 1, https://wwwnc.cdc.gov/EID/ article/27/6/20-4557-App1.pdf).The French Armed Forces (FAF) have served in Djibouti for decades. Service members and their families (≈2,700 persons) live in the capital. Despite malaria prevention and treatment measures described elsewhere (6), an outbreak among French military personnel occurred in February 2019; failure of early artemisinin combined therapy was documented in 1 patient. The StudyWe collated FAF epidemiologic surveillance data on malaria cases among service members in Djibouti during 1993Djibouti during -2019; the 2019 data included cases among family members. We defi ned a malaria case as an illness resulting in a positive result on a rapid diagnostic test or thin blood smear.We conducted the fi eld investigation in the capital during February 28-March 22, 2019. We obtained a dried blood spot on fi lter paper from each patient and stored the samples in a sealed plastic pouch until processing. We extracted DNA from the samples and

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“…stephensi . Also, there is evidence of diverse insecticide resistance mechanisms among Anopheles species [ 15 – 17 ]. Given these differences, vector control approaches are in the process of being modified to account for the presence of An.…”

Section: Introductionmentioning

confidence: 99%

Genetic diversity of Anopheles stephensi in Ethiopia provides insight into patterns of spread

et al. 2021

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Background 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. 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. Methods 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. 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. Results Six 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. Conclusion We 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 Abstract

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Insecticide resistance in Anopheles stephensi in Somali Region, eastern Ethiopia

Cited by 63 publications

References 30 publications

An update on the distribution, bionomics, and insecticide susceptibility of Anopheles stephensi in Ethiopia, 2018–2020

An update on the distribution, bionomics, and insecticide susceptibility of Anopheles stephensi in Ethiopia, 2018–2020

Role of Anopheles stephensi Mosquitoes in Malaria Outbreak, Djibouti, 2019

Genetic diversity of Anopheles stephensi in Ethiopia provides insight into patterns of spread

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