281 - Genetic Structure and Evidence of Introgression in Saudi Arabian Aedes aegypti Populations

Abstract: The Aedes aegypti (Linnaeus, 1762) mosquito is a primary vector for several arboviruses, including dengue, chikungunya, and Zika, and is now established globally. This species includes two genetically distinct forms: an ancestral African form (Aedes aegypti formosus), which is prevalent throughout Africa, and a domestic form (Aedes aegypti aegypti) that has spread across the tropics and subtropics. In Saudi Arabia, A. aegypti was first documented in the southwestern region in 1956, with prior studies aligning Saudi populations with the global domestic lineage. However, recent findings suggest a more complex genetic structure, potentially due to gene flow from African populations into local Saudi populations.

This study aimed to characterize the genetic differentiation and evidence of introgression in Saudi A. aegypti populations by analyzing samples from two key regions (west and south) using a 25K SNP genotyping platform. Results revealed two distinct genetic clusters, corresponding to the sampled regions, with signs of introgression from African A. aegypti formosus into southern populations, particularly in Jazan and surrounding areas. A focused genomic scan of the Jazan Mountain population highlighted unique SNP distributions, identifying nearly 1,400 differentiated SNPs, suggesting significant genetic variation influenced by geographic and environmental factors.

These findings underscore the unique genetic diversity of A. aegypti in Saudi Arabia and may have important implications for understanding local transmission dynamics and vector control efforts, given the potential for genetic traits that influence vector competence to be introduced via introgression from African populations.