Geographical distribution of Anopheles stephensi in eastern Ethiopia

Abstract

Background: The recent detection of the South Asian malaria vector Anopheles stephensi in Ethiopia and other regions in the Horn of Africa has raised concerns about its potential impact on malaria transmission. We report here the findings of a survey for this species in eastern Ethiopia using both morphological and molecular methods for species identification.

Methods: Adult and larval/pupal collections were conducted at ten sites in eastern Ethiopia and Anopheles specimens were identified using standard morphological keys and genetic analysis.

Results: In total, 2231 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 c oxidase subunit 1 (cox1) 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.

Conclusions: Our 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.

Keywords: Anopheles stephensi; Ethiopia; Horn of Africa; Malaria.

Fig. 1

Map of study sites in Ethiopia

Fig. 2

Examples of breeding sites where An. stephensi larvae and pupae were found: a water tank trucks; b construction water storage reservoirs; c discarded tires; d buckets; e steel drums; f water tanks; g temporary water storage reservoirs; h birkas