Serological Biomarkers for Monitoring Human-Vector Contact by Invasive Anopheles stephensi in Africa

Project Summary Serological Biomarkers for Monitoring Human-Vector Contact by Invasive Anopheles stephensi in Africa Anopheles stephensi was historically considered a major malaria vector in urban environments in Southeast Asia, the Middle East and the Arabian Peninsula. Since its first detection in Djibouti in 2012, the distribution of this vector species has expanded to Ethiopia, Sudan and Somalia in the Horn of Africa, and Nigeria in west Africa. Establishment and spread of An. stephensi in Africa pose major challenges for malaria control and elimination in fast-growing urban Africa because An. stephensi is a confirmed vector for local African Plasmodium falciparum and P. vivax strains and is resistant to multiple classes of synthetic insecticides. Accordingly, the World Health Organization recently established an initiative to take concerted actions to stop the spread of An. stephensi by improving surveillance and control of this species in Africa. However, the commonly- used mosquito surveillance methods such as CDC light traps, human landing catches and larval dipping methods lack the necessary sensitivity in urban settings due to environmental light pollution and low vector abundance. However, sensitive surveillance of An. stephensi is critical to its early detection and control. Recently, serological methods for monitoring human-vector contact by measuring antibody response to mosquito salivary proteins have been developed. However, the available serological method is based on well-conserved proteins and cannot be used to differentiate An. stephensi exposure from those of native Anopheles species. The objective of this R21 application is to develop serological biomarkers that can distinguish exposure to invasive An. stephensi from the native African malaria vector species using novel peptide microarray technology. Two aims are proposed: 1) identify salivary peptides that distinguish the exposure of invasive An. stephensi from the native African malaria vector species, An. arabiensis, using novel peptide microarray technology; and 2) evaluate candidate salivary peptides using human plasma from field sites with contrasting An. stephensi distribution in Ethiopia. The new tool from this project can be used to measure human-vector contact with the invasive An. stephensi, and thus help assess the role of An. stephensi in malaria transmission. Serological biomarkers have the potential to be utilized in domesticated animals, the main blood source for An. stephensi mosquitoes. This could enhance the detection sensitivity of invasive An. stephensi mosquitoes, thereby facilitating the surveillance and control of An. stephensi populations in Africa.