An investigation of malaria vector populations in Turkana, Kenya to understand the potential impact of insecticide-treated nets.

The malaria ecology of northern Kenya differs significantly from the rest of the country. Transmission is highly seasonal and intense, despite the arid environment and low population density. The region faces several threats to malaria control including identification of significant P. vivax infection and an emerging invasive vector species, An. stephensi. Our understanding of malaria in Turkana has evolved significantly in the last 5 years, from being considered low risk and epidemic-prone to being classified as one of the highest transmission areas in the country. Turkana County implemented its first mass bednet distribution in late 2024. Prior to this campaign, we established a surveillance program to understand mosquito density, vector species diversity, host preference and contribution to malaria transmission. We captured mosquitoes in traps baited with CO2 and human odors in rural and peri-urban areas, indoors and outdoors, over 1 year. Twenty-percent of female anophelines were captured outdoors but the proportion infected with P. falciparum was higher in outdoor collections. An. coluzzii, a vector commonly found in West Africa, was the second most abundant species and had the highest P. falciparum infection rates. These data will be useful in predicting the impact of ITN distribution in this unique context.