Are the sterile insect technique and the incompatible insect techniques effective in reducing Aedes mosquito populations?

BackgroundThe control of Aedes aegypti and Aedes albopictus mosquitoes, the main vectors of dengue, chikungunya and Zika viruses, presents several challenges. The difficulties encountered in acquiring funding, implementing measures, obtaining community participation, acceptability and effectiveness, and the problem of insecticide resistance demonstrate the need to develop and optimise innovative vector control strategies. The sterile insect technique (SIT), the incompatible insect technique (IIT) and a combination of both (SIT-IIT) show promise. Numerous trials are being carried out worldwide to obtain evidence of their effectiveness before implementing them in large-scale, integrated vector-control strategies. The main objective of our study is to build an analytical framework for the identification and standardisation of appropriate entomological indicators that could be used to compare the relative effectiveness of the SIT, IIT and SIT-IIT methods in reducing Aedes vector populations. MethodsWe reviewed the available scientific literature to compare the characteristics, methodologies, effectiveness indicators and results of various trials with the aim of standardising and comparing the indicators used in the trials, such as reductions in the egg hatch rate and in the adult populations. ResultsSeventeen trials, either published in peer-reviewed journals or posted as preprints, were selected. We found wide variation among them in experimental design, field implementation and the methods of calculating the indicators. Although limited by the amount of available published data, our results suggest that a reduction in egg hatching greater than 45% results in up to 60% fewer females, greater than 60% results in over 80% fewer females, and greater than 70% results in over 90% fewer females. Therefore, the quality of implementation, assessed on the basis of egg hatch reduction, is statistically associated with effectiveness, assessed on the basis of the reduction in Aedes females. ConclusionWe present results suggesting that, when implemented effectively, the incompatible and sterile insect techniques are substantially effective in reducing Aedes mosquito populations. Furthermore, these techniques are species specific, non-insecticidal and environmentally friendly. However, it has yet to be shown that they can be scaled up as cost-effective operational tools for vector control and that they substantially reduce arbovirus transmission.