Genetic characterization of Aedes aegypti (Diptera: Culicidae) in Sri Lanka based on COI gene.

BACKGROUND & OBJECTIVES: Aedes aegypti is the most prominent vector for dengue virus worldwide. Accurate identification of the species and understanding its colonization pattern are essential prerequisites in vector control. Thus, the present study was aimed to genetically characterize Ae. aegypti mosquitoes collected from different regions of Sri Lanka based on mitochondrial COI gene. METHODS: Thirty-three Ae. aegypti larval samples were collected from 19 districts. A 735bp region of the mitochondrial COI gene was amplified and analyzed for genetic diversity indices. Phylogenetic trees were constructed using Sri Lankan samples and also including mosquito samples reported from other parts of the world. RESULTS: High genetic diversity was observed within the samples analysed (gene diversity: 0.949; average number of nucleotide differences: 6.371). There were 20 haplotypes presented within the 19 localities investigated. The phylogenetic tree derived two main clades. However, no distinguishable clustering pattern was observed in the phylogenetic tree except for the districts in the northern corner indicating extensive admixing among different populations. When samples from other countries were included in the phylogenetic tree, Anuradhapura, and Mannar samples were clustered together with samples from India, Venezuela, USA, Portugal and Cambodia while Rathnapura was clustered with Bolivia and France. INTERPRETATION & CONCLUSION: Our results suggest that Sri Lanka has undergone multiple invasions of Ae. aegypti from various parts of the world over an extensive period. Further, the mosquito control campaigns had not caused a significant effect on the Ae. aegypti populations which is existing in mutation-drift equilibrium.