Strategic Approach, Advances, and Challenges in the Development and Application of the SIT for Area-Wide Control of Aedes albopictus Mosquitoes in Reunion Island

Abstract

The global expansion of Aedes albopictus, together with the absence of specific treatment and vaccines for most of the arboviruses it transmits, has stimulated the development of more sustainable and ecologically acceptable methods for control of disease transmission through the suppression of natural vector populations. The sterile insect technique (SIT) is rapidly evolving as an additional tool for mosquito control, offering an efficient and more environment-friendly alternative to the use of insecticides. Following the devastating chikungunya outbreak, which affected 38% of the population on Reunion Island (a French overseas territory in the southwest of the Indian Ocean), there has been strong interest and political will to develop effective alternatives to the existing vector control strategies. Over the past 10 years, the French Research and Development Institute (IRD) has established an SIT feasibility program against Ae. albopictus on Reunion Island in collaboration with national and international partners. This program aimed to determine whether the SIT based on the release of radiation-sterilized males is scientifically and technically feasible, and socially acceptable as part of a control strategy targeting the local Ae. albopictus population. This paper provides a review of a multi-year and a particularly broad scoping process of establishing the scientific and technological feasibility of the SIT against Ae. albopictus on Reunion Island. It also draws attention to some prerequisites of the decision-making process, through awareness campaigns to enhance public understanding and support, social adoption, and regulatory validation of the SIT pilot tests.

Keywords: Aedes albopictus; feasibility study; irradiation; sterile insect technique.

Figure 1

Strategic plan for developing and applying the sterile insect technique (SIT) against Aedes albopictus on Reunion Island. Legend. This figure summarizes the short, medium, and long-term SIT development plans. The strategic framework contains the necessary steps that should be taken to determine the overall strength of evidence (establish lines of evidence and knowledge gaps) needed when developing or applying SIT approaches for vector control [41]. The proposed strategy has been a continuous process of step-wise decision-making in response to scientific progress and technological development. The planned strategic option of SIT application against Ae. albopictus in Reunion Island focuses on suppression, rather than eradication [31], which is an almost unattainable goal.

Figure 2

Aerial view of the two field sites: (A) Duparc and (B) Bois Rouge for SIT pilot testing in Reunion Island. Yellow and red circles indicate the positions of individual ovitraps and BG sentinel traps, respectively, while green circles show the parcels where both ovitraps and BG sentinel traps were deployed for Aedes albopictus population monitoring.

Figure 3

Dose-response curves of the sterility and mating competitiveness of sterile Aedes albopictus males from laboratory reared colony. Legend. The dose-sterility tests (unpublished data) were performed in laboratory cages while the mating competitiveness experiments were conducted in field cages. In all studies, mass-reared males were sterilized by X-ray radiation at 35Gy. Equal numbers of wild males, wild females, and mass-reared males were used in dose-sterility tests, whereas the competitiveness assays [54] tested the relationship between varying ratios of sterile to wild males and egg sterility (Re-drawn from [54]).

Figure 4

Index of overall social support of different mosquito control technologies.