Invasive Anopheles stephensi in Ghana: Sampling Tools and Vector Population Dynamics

Project summary
Title: Invasive Anopheles stephensi in Ghana: Sampling Tools and Vector Population Dynamics
Anopheles stephensi, an invasive mosquito species originating from Southeast Asia and the Arabian Peninsula,
has been expanding its spread in Africa over the past decade. It was first detection in Djibouti, the Horn of Africa,
in 2012, and this event was associated with an outbreak of urban malaria. The vector has later been found in
Ethiopia in 2016 and 2018, Sudan in 2016, Somalia in 2019, Nigeria in 2020 and Kenya in 2023. The most recent
discovery of Anopheles stephensi was made in Ghana in March 2023. The discovery of An. stephensi in Ghana
is concerning due to significant knowledge gaps on the extent of spread, densities in sentinel sites and the
bionomics of An. stephensi. It has been observed that the larval ecology of An. stephensi in Ghana differs
substantially from what has been reported in the Indian subcontinent and in East Africa. Consequently, there is
a pressing need for increased research efforts to gain a deeper understanding of the larval ecology and
bionomics of this invasive species in Ghana. Moreover, the most efficient surveillance tool for An. stephensi and
other native urban African mosquito vectors have not been systematically evaluated. Data on the spread,
bionomics and sampling tools for An. stephensi is very important for making informed decisions regarding
effective interventions for An. stephensi control and elimination in Ghana. The central objective of this application
is to compare sampling tools for invasive An. stephensi and native malaria vectors, and determine the
extent of spread, densities and characterize the bionomics of An. stephensi in Ghana. The long-term goal
is to develop evidence-based sampling tools for systematic An. stephensi surveillance to enable sensitive
detection of invasion events, track the spread, and facilitate the evaluation of intervention measures. To achieve
this objective, two specific aims have been designed. In aim 1, we will systematically evaluate sampling methods
for An. stephensi and other native malaria vectors in heterogeneous urban environments. This aim will provide
data on the extent of the spread of An. stephensi and the efficient sampling tools for An. stephensi. This data
will give a better understanding of the gaps in protection, optimizing present strategies and supplemental
strategies needed to mitigate invasions. In aim 2, we will determine the extent of An. stephensi spread and
population dynamics of malaria vectors in sentinel sites in Ghana. Data from this will provide a better
understanding of the extent of spread and the mechanisms that regulate An. stephensi breeding and productivity.
Overall, data from these aims will increase our understanding of the most appropriate sampling methods for the
surveillance, the extent of spread and factors that regulate An. stephensi and native vector populations in urban
cities in Ghana. It will also provide evidence for the most efficient intervention strategies that may be particularly
effective against these invasive species.

Grant Number: 5R03AI186018-02
NIH Institute/Center: NIH
Principal Investigator: YAW AFRANE