Vectorial Capacity of Invasive Anopheles stephensi in Ethiopia

About This Grant

Project Summary Project title: Vectorial Capacity of Invasive Anopheles stephensi in Ethiopia Anopheles stephensi is a major malaria vector in urban environments in South Asia, the Middle East, and the Arabian Peninsula. Since its first detection in Djibouti in 2012, it has spread to Ethiopia, Sudan, Eritrea, Somalia, Kenya, Ghana, Niger and Nigeria in Africa. Unlike the native African malaria vectors such as An. gambiae and An. arabiensis, which are not well-adapted to urban settings, An. stephensi thrives in dense urban environments. Although the invasion of Anopheles stephensi has been regarded as a major threat to malaria control and elimination efforts in Africa, its precise role in sustaining and amplifying malaria transmission on the continent remains poorly understood. Currently, the estimation of geographic areas suitable for An. stephensi vector survival based on climatic conditions is used to assess the malaria risk posed by An. stephensi invasion. This is insufficient because malaria transmission depends not only on the vector’s presence but also on other biological traits such as vector competence, survivorship and human feeding rate. The central objective of this project is to examine vector competence of invasive An. stephensi for local Plasmodium falciparum and P. vivax, and determine its malaria vectorial capacity under field conditions in Ethiopia, thereby providing a more accurate assessment of the malaria risk associated with the invasion of An. stephensi. The project has two aims: 1) Determine the vector competence of invasive An. stephensi for local isolates of P. falciparum and P. vivax, as well as association between mosquito immunity gene polymorphisms and vector competence; and 2) Examine the survivorship, human feeding rate and malaria vectorial capacity of An. stephensi under field conditions in Ethiopia. This research will directly address the current debate regarding the role of invasive An. stephensi in malaria transmission in Africa and provide essential information on the malaria risks associated with its spread. Quantifying the transmission risk posed by An. stephensi is critical for determining whether existing malaria control strategies require modification to effectively manage this emerging urban vector in Africa. If An. stephensi is confirmed to be an efficient malaria vector in Africa, malaria control programs will need to explicitly incorporate this species into the planning and consider its unique ecology and the distinct characteristics of urban malaria transmission. This will likely require strategies that go beyond the conventional bednet-based approaches designed for rural settings, such as targeted larval source management and integrating vector control into urban planning and infrastructure development.