Geographical distribution of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and genetic diversity of invading population of Ae. albopictus in the Republic of the Congo [version 3; referees: 3 approved]

Background: The arbovirus vector, Aedes albopictus, originating from Asia, has recently invaded African countries, including the Republic of the Congo, where it was associated with a chikungunya outbreak. Up until now, little was known about its distribution in relation to the native Aedes aegypti and how the invasion will modify the epidemiology of arboviral diseases. Here, we assessed the current distribution of Ae. albopictus and Ae. aegypti in the Republic of the Congo and explored the genetic diversity of the invading species, Ae. albopictus. Methods: Immature stages of Aedes were collected in nine locations in the Republic of the Congo in 2017 following a north-south transect and reared to adult stage. Adults were morphologically identified, counted and grouped according to species and location. Genetic diversity of Ae. albopictus was assessed by analyzing the cytochrome oxidase I (COI) gene. Results: Ae. albopictus and Ae. aegypti were found together across the country in all the locations investigated. The invasive species is predominant over the native species in all locations except Brazzaville, suggesting that Ae. albopictus is displacing Ae. aegypti across Congo. When comparing the species distributions across the two largest cities, Brazzaville and Pointe Noire, Ae. albopictus was more prevalent than Ae. aegypti in the suburbs whereas the opposite situation was reported in the city centre. Mitochondrial DNA analysis revealed very low genetic diversity of Ae. albopictus with only three haplotypes recorded across the country supporting the recent introduction of this species in the Republic of the Congo. Phylogenetic tree analysis revealed that Ae. albopictus from Congo originated from other tropical Asian countries such as China, likely as a result of increasing trade links. Conclusion: These findings are important for the implementation of vector control strategies and can serve as a foundation for further research on these vectors in the country.