Public health impact of the spread of Anopheles stephensi in the WHO Eastern Mediterranean Region countries in Horn of Africa and Yemen: need for integrated vector surveillance and control.

BACKGROUND: Anopheles stephensi is an efficient vector of both Plasmodium falciparum and Plasmodium vivax in South Asia and the Middle East. The spread of An. stephensi to countries within the Horn of Africa threatens progress in malaria control in this region as well as the rest of sub-Saharan Africa. METHODS: The available malaria data and the timeline for the detection of An. stephensi was reviewed to analyse the role of An. stephensi in malaria transmission in Horn of Africa of the Eastern Mediterranean Region (EMR) in Djibouti, Somalia, Sudan and Yemen. RESULTS: Malaria incidence in Horn of Africa of EMR and Yemen, increased from 41.6 in 2015 to 61.5 cases per 1000 in 2020. The four countries from this region, Djibouti, Somalia, Sudan and Yemen had reported the detection of An. stephensi as of 2021. In Djibouti City, following its detection in 2012, the estimated incidence increased from 2.5 cases per 1000 in 2013 to 97.6 cases per 1000 in 2020. However, its contribution to malaria transmission in other major cities and in other countries, is unclear because of other factors, quality of the urban malaria data, human mobility, uncertainty about the actual arrival time of An. stephensi and poor entomological surveillance. CONCLUSIONS: While An. stephensi may explain a resurgence of malaria in Djibouti, further investigations are needed to understand its interpretation trends in urban malaria across the greater region. More investment for multisectoral approach and integrated surveillance and control should target all vectors particularly malaria and dengue vectors to guide interventions in urban areas.

Confirmation of the presence of Anopheles stephensi among internally displaced people's camps and host communities in Aden city, Yemen.

BACKGROUND: Declines in global malaria cases and deaths since the millennium are currently challenged by multiple factors including funding limitations, limits of, and resistance to vector control tools, and also recent spread of the invasive vector species, Anopheles stephensi-especially into novel urban settings where malaria rates are typically low. Coupled with general increases in urbanization and escalations in the number of conflicts creating rapid and unplanned population displacement into temporary shelter camps within host urban areas, particularly in the Middle East and sub-Saharan Africa, increased urban malaria is a major threat to control and elimination. METHODS: Entomological monitoring surveys (targeting Aedes aegypti) of water containers across urban areas hosting internally displaced people (IDP) communities in Aden city, Yemen, were performed by The MENTOR Initiative, a non-governmental organisation. As part of these surveys in 2021 23 larvae collected and raised to adults were morphologically identified as An. stephensi. Twelve of the samples were sent to Liverpool School of Tropical Medicine for independent morphological assessment and genetic analysis by sequencing the ribosomal ITS2 region and the mitochondrial COI gene. RESULTS: All twelve samples were confirmed morphologically and by sequence comparison of the single ITS2 and COI haplotype detected to the NCBI BLAST database as An. stephensi. Phylogenetic analysis with comparable COI sequences indicated close relationship to haplotypes found in Djibouti and Ethiopia. CONCLUSION: The study results confirm the presence of An. stephensi in Yemen. Confirmation of the species in multiple urban communities hosting thousands of IDPs living in temporary shelters with widescale dependency on open water containers is of particular concern due to the vulnerability of the population and abundance of favourable breeding sites for the vector. Proactive monitoring and targeted integrated vector management are required to limit impacts in this area of typically low malaria transmission, and to prevent further the spread of An. stephensi within the region.