Insecticide resistance and population structure of the invasive malaria vector, Anopheles stephensi, from Fiq, Ethiopia

Anopheles stephensi invasion in Ethiopia poses a risk of increased malaria disease burden in the region. Thus, understanding the insecticide resistance profile and population structure of the recently detected An. stephensi population in Fiq, Ethiopia, is critical to inform vector control to stop the spread of this invasive malaria species in the country. Following entomological surveillance for An. stephensi in Fiq, Somali region, Ethiopia, we confirmed the presence of An. stephensi morphologically and molecularly in Fiq. Characterization of larval habitats and insecticide susceptibility tests revealed that Fiq An. stephensi is most often found in artificial containers and is resistant to most adult insecticides tested (organophosphates, carbamates, pyrethroids) except for pirimiphos-methyl and PBO-pyrethroids. However, the immature larval stage was susceptible to temephos. Further comparative genomic analyses with previous An. stephensi populations from Ethiopia using 1704 biallelic SNPs revealed genetic relatedness between Fiq An. stephensi and east-central Ethiopia An. stephensi populations, particularly Jigjiga An. stephensi. Our findings of the insecticide resistance profile, coupled with the likely source population of Fiq An. stephensi, can inform vector control strategies against this malaria vector in Fiq and Jigjiga to limit further spread out of these two locations to other parts of the country and continent.