Sequence-based identification of Anopheles species in eastern Ethiopia

Shantoy Hansel,Karen Lopez,Daniel Janies,Solomon Yared,Tamar E. Carter

doi:10.1186/s12936-019-2768-0

Shantoy Hansel, Karen Lopez + Show 3 more

Open Access

https://doi.org/10.1186/s12936-019-2768-0

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Abstract

BackgroundThe recent finding of a typically non-African Anopheles species in eastern Ethiopia emphasizes the need for detailed species identification and characterization for effective malaria vector surveillance. Molecular approaches increase the accuracy and interoperability of vector surveillance data. To develop effective molecular assays for Anopheles identification, it is important to evaluate different genetic loci for the ability to characterize species and population level variation. Here the utility of the internal transcribed spacer 2 (ITS2) and cytochrome oxidase I (COI) loci for detection of Anopheles species from understudied regions of eastern Ethiopia was investigated.MethodsAdult mosquitoes were collected from the Harewe locality (east) and Meki (east central) Ethiopia. PCR and Sanger sequencing were performed for portions of the ITS2 and COI loci. Both NCBI’s Basic Local Alignment Search tool (BLAST) and phylogenetic analysis using a maximum-likelihood approach were performed to identify species of Anopheles specimens.ResultsTwo species from the east Ethiopian collection, Anopheles arabiensis and Anopheles pretoriensis were identified. Analyses of ITS2 locus resulted in delineation of both species. In contrast, analysis of COI locus could not be used to delineate An. arabiensis from other taxa in Anopheles gambiae complex, but could distinguish An. pretoriensis sequences from sister taxa.ConclusionThe lack of clarity from COI sequence analysis highlights potential challenges of species identification within species complexes. These results provide supporting data for the development of molecular assays for delineation of Anopheles in east Ethiopia.

Highlights

The recent finding of a typically non-African Anopheles species in eastern Ethiopia emphasizes the need for detailed species identification and characterization for effective malaria vector surveillance
All Anopheles gambiae complex specimens from this collection in Ethiopia were identical for internal transcribed spacer 2 (ITS2) sequences
When the consensus ITS2 sequence from Ethiopia were searched against National Center for Biotechnology Information (NCBI) with Basic Local Alignment Search tool (BLAST), specimens from Ethiopia formed High-scoring Segment Pairs (HSP) with ~ 99% identity for Anopheles arabiensis

Summary

Introduction

The recent finding of a typically non-African Anopheles species in eastern Ethiopia emphasizes the need for detailed species identification and characterization for effective malaria vector surveillance. To develop effective molecular assays for Anopheles identification, it is important to evaluate different genetic loci for the ability to characterize species and population level variation. While strides to control the transmission of malaria likely contributed to the reduction in overall mortality and incidence over the last several decades [2], continued understanding of the mosquito vector populations are needed for improved targeted interventions [3]. A recent study revealed the presence of Anopheles stephensi, a malaria vector species typically only seen east of the Red Sea [4]. Due to the global variation of Anopheles species and populations, it is vital to evaluate techniques specific to east Ethiopia to identify various Anopheles species [3, 5]. Morphological identification can be tedious when processing many specimens and comes with risk for misidentification of species not previously encountered

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Conclusion