Pilot trial using mass field-releases of sterile males produced with the incompatible and sterile insect techniques as part of integrated Aedes aegypti control in Mexico

Abstract

BackgroundThe combination ofWolbachia-based incompatible insect technique (IIT) and radiation-based sterile insect technique (SIT) can be used for population suppression ofAedes aegypti. Our main objective was to evaluate whether open-field mass-releases ofwAlbB-infectedAe.aegyptimales, as part of an Integrated Vector Management (IVM) plan led by the Mexican Ministry of Health, could suppress natural populations ofAe.aegyptiin urbanized settings in south Mexico.Methodology/Principal findingsWe implemented a controlled before-and-after quasi-experimental study in two suburban localities of Yucatan (Mexico): San Pedro Chimay (SPC), which received IIT-SIT, and San Antonio Tahdzibichén used as control. Release ofwAlbBAe.aegyptimales at SPC extended for 6 months (July-December 2019), covering the period of higherAe.aegyptiabundance. Entomological indicators included egg hatching rates and outdoor/indoor adult females collected at the release and control sites. Approximately 1,270,000 lab-producedwAlbB-infectedAe.aegyptimales were released in the 50-ha treatment area (2,000wAlbBAe.aegyptimales per hectare twice a week in two different release days, totaling 200,000 male mosquitoes per week). The efficacy of IIT-SIT in suppressing indoor femaleAe.aegyptidensity (quantified from a generalized linear mixed model showing a statistically significant reduction in treatment versus control areas) was 90.9% a month after initiation of the suppression phase, 47.7% two months after (when number of released males was reduced in 50% to match local abundance), 61.4% four months after (when initial number of released males was re-established), 88.4% five months after and 89.4% at six months after the initiation of the suppression phase. A proportional, but lower, reduction in outdoor femaleAe.aegyptiwas also quantified (range, 50.0–75.2% suppression).Conclusions/SignificanceOur study, the first open-field pilot implementation ofWolbachiaIIT-SIT in Mexico and Latin-America, confirms that inundative male releases can significantly reduce natural populations ofAe.aegypti. More importantly, we present successful pilot results of the integration ofWolbachiaIIT-SIT within a IVM plan implemented by Ministry of Health personnel.