First report of African malaria vector Anopheles gambiae (Diptera: Culicidae) from Ethiopia

Abstract

Introduction: Reports of different researches conducted in Ethiopia consistently implicated An. arabiensis as the primary vector and An. pharoensis, An. funestus and An. nili as secondary vectors. These facts prevailed until today as the vectorial roles of the rest of Anopheles are not yet well known due to several limitations. This indicates that there is a need to identify other potential or suspected Anopheles species. The aims of this study were to determine Anopheline mosquito fauna, abundance and characterize mosquito breeding habitats in selected study sites in Ethiopia.
Materials and methods: A longitudinal study design with purposive and multi-stage sampling technique was conducted in Southern Nations Nationalities Peoples Region of Ethiopia. The study was carried out in Jolie and Gogete study sites from Meskan and Sodo districts, respectively. A total of 4,118 third and fourth instars larvae of Anopheles mosquitoes were collected. Morover, a total of 4,461 indoor adult female Anopheles were caught from both study sites. Identifications of Anopheles species were done using morphological keys under a compound microscope and polymerase chain reaction test for sibling species detection.
Results: Of the 4,118 samples collected ten Anopheles species from Jolie study site and eleven from Gogete study site were identified. Tewenty sever percent of the Anopheles larvae were collected from marshy breeding site. In both study sites the predominant Anopheles species was An. gambiae s.l. which is accountable for malaria transmission. Seasonal variations (between dry and wet season) statistically significant differences (P=0.001) in Jolie and in Gogete (P=0.001) study sites were observed in Anopheles larval collection. . In Jolie and Gogete study sites An. gambiae s.l. was found to be the predominant species making up 64% and 64%, respectively. Statistically significant differences were observed in mean adult An. gambiae s.l. (P=0.002) and An. pharoensis (P=0.001) collection among the study sites. Besides, statistically significant (P=0.001) variations between wet and dry seasons were observed in the number of adult An. gambiae s.l. populations in both study sites. Of 239 An. gambiae s.l. analyzed by PCR, 94.1% were identified as An. arabiensis and 5.9% were identified as An. gambiae.

Conclusion: In the present study An. gambiae was reported for the first time in Ethiopia indicating the presence of the highly efficient vector in Ethiopia, thus establishing appropriate control strategy for this species might be necessary. The breeding habitats of Anopheles mosquitoes in the study sites particularly in the dry season were due to anthropogenic activities rather than environmental factors that require larval control.