Cross-Mating Compatibility and Competitiveness among Aedes albopictus Strains from Distinct Geographic Origins - Implications for Future Application of SIT Programs in the South West Indian Ocean Islands

Abstract

The production of large numbers of males needed for a sustainable sterile insect technique (SIT) control program requires significant developmental and operational costs. This may constitute a significant economic barrier to the installation of large scale rearing facilities in countries that are undergoing a transition from being largely dependent on insecticide use to be in a position to integrate the SIT against Aedes albopictus. Alternative options available for those countries could be to rely on outsourcing of sterile males from a foreign supplier, or for one centralised facility to produce mosquitoes for several countries, thus increasing the efficiency of the mass-rearing effort. However, demonstration of strain compatibility is a prerequisite for the export of mosquitoes for transborder SIT applications. Here, we compared mating compatibility among Ae. albopictus populations originating from three islands of the South Western Indian Ocean, and assessed both insemination rates and egg fertility in all possible cross-mating combinations. Furthermore, competitiveness between irradiated and non-irradiated males from the three studied strains, and the subsequent effect on female fertility were also examined. Although morphometric analysis of wing shapes suggested phenoptypic differences between Ae. albopictus strains, perfect reproductive compatibility between them was observed. Furthermore, irradiated males from the different islands demonstrated similar levels of competitiveness and induced sterility when confronted with fertile males from any of the other island populations tested. In conclusion, despite the evidence of inter-strain differences based on male wing morphology, collectively, our results provide a new set of expectations for the use of a single candidate strain of mass-reared sterile males for area-wide scale application of SIT against Ae. albopictus populations in different islands across the South Western Indian Ocean. Cross-mating competitiveness tests such as those applied here are necessary to assess the quality of mass reared strains for the trans-border application of sterile male release programs.

Concerns about the feasibility of using “precision guided sterile males” to control insects

“…The latter figure was however obtained in the field 2 and the same strain had a competitiveness of 100% against various field strains under semi-field conditions 3 which are more realistic than “fly vials”. Similarly, a competitiveness of 72–100% was observed for irradiated male Aedes albopictus under semi-field conditions 4 and of 40–80% in another study 5 . These data contradict their claim that “these results suggest that pgSIT has greater potential to eliminate local Ae.…”

Demonstration of resistance to satyrization behavior in Aedes aegypti from La Réunion island

“…When considering a regional approach for Aedes control using the SIT, compatibility of strains as well as species may be important as it would allow strains to be imported for release from nearby countries where they can be more easily reared and/or irradiated. Damiens et al [18] demonstrated that male Ae. albopictus from Mauritius and Seychelles islands, about 50-200 km away from La Réunion island, were compatible and could successfully inseminate female Ae.…”

Sexual Competitiveness and Induced Egg Sterility by Aedes aegypti and Aedes albopictus Gamma-Irradiated Males: A Laboratory and Field Study in Mexico

“…albopictus at differing ratios of fertile males:irradiated males in both laboratory and field-cage conditions. The study was performed on the Mexican populations of these mosquitoes as irradiated male mating competitiveness can differ between insect populations, so the findings from one region may differ quantitatively or qualitatively from those in geographically distant regions [ 11 , 22 ]. As such, the results of the present study will serve to estimate the minimum required release ratio of sterile males to wild males that could suppress the natural populations of these vectors in a dengue-endemic region of southern Mexico.…”