Evidence of Habitat Structuring Aedes albopictus Populations in Réunion Island

Abstract

Arbovirus vector dynamics and spread are influenced by climatic, environmental and geographic factors. Major Chikungunya and Dengue fever outbreaks occurring the last 10 years have coincided with the expansion of the mosquito vector Aedes albopictus to nearly all the continents. We characterized the ecological (larval development sites, population dynamics, insemination and daily survival rates) and genetic (diversity, gene flow, population structure) features of two Aedes albopictus populations from distinct environments (rural and urban) on Réunion Island, in the South-West Indian Ocean. Microsatellite analysis suggests population sub-structuring Ae. albopictus populations. Two genetic clusters were identified that were significantly linked to natural versus urban habitats with a mixed population in both areas. Ae. albopictus individuals prefer urban areas for mating and immature development, where hosts and containers that serve as larval development sites are readily available and support high population densities, whereas natural environments appear to serve as reservoirs for the mosquito. The objective of our research was to study the movements the mosquito Aedes albopictus. This mosquito transmits more than 20 viruses to humans throughout the world and is the vector of the recent major epidemics of Dengue and Chikungunya on Reunion Island and the Indian Ocean Region and is, therefore, of great interest for human health. We set out to determine whether reservoirs of populations could be found in natural environments and whether or not these populations are capable of re-colonising urban areas. Until now, only limited data has been available on the population dynamics of Aedes albopictus in this part of the world, information critical for guiding vector control strategies and predicting or preventing epidemics. We chose two areas where a serious CHIKV epidemic occurred. We then used genetic markers and ecological data to estimate patterns of gene flow and behaviour. We were able to demonstrate that populations were structured with limited gene flow despite observing migration. We found that Ae. albopictus preferred urban areas for mating and to lay their eggs because of the availability of hosts and permanent containers that favoured higher mosquito densities. We also show, however, that natural environments are reservoirs for re-colonisation of urban areas.