Vector control: the OpTIS project has entered its operational phase

The OpTIS project (Operationalisation of the Sterile Insect Technique against Aedes vectors of disease in Réunion)* has entered its operational phase, with the first releases of treated sterile male mosquitoes in Langevin, Réunion.

Before this project, IRD and CIRAD had already implemented two flagship projects in this field. Since 2009, IRD has led a feasibility study followed by the launch of a pilot SIT trial in Sainte-Marie (Réunion) targeting Aedes albopictus. This pilot trial, conducted from July 2021 to July 2022, achieved an induced sterility rate of more than 60%. From 2016 to 2021, CIRAD coordinated the REVOLINC research project in partnership with IRD and with funding from the European Research Council (ERC), which led to a pilot trial of “boosted SIT” against Aedes aegypti in Saint-Joseph in 2021. By the end of the trial, this population had been reduced by 91%, with a smaller reduction in Aedes albopictus densities.

The OpTIS project, jointly led by these two institutes with support from the Saint-Joseph municipality, aims to assess the effectiveness and social acceptability of “boosted SIT”, this time targeting the main vector of dengue in Réunion, Aedes albopictus. In this boosted version, SIT is strengthened by the use of a larvicide, pyriproxyfen, a third-generation biocide used at very low concentrations (ten times lower than the WHO’s recommended dose in drinking water) and in a targeted manner in both space and time.

The OpTIS project has several objectives: 

• To overcome the biological limitations of SIT linked to the influx of fertile females into the control area and/or density-dependent mortality of larvae in breeding sites;
• To reduce the cost of producing sterile male mosquitoes, making industrial-scale production more feasible;
• To assess public perception and acceptance of this innovative vector control technology;
• To define new integrated strategies for vector control and epidemic risk prevention/reduction, combining this tool with conventional SIT and the elimination of breeding sites, in a targeted manner in both space and time, leading to a significant reduction in insecticide use;
• To transfer the technology to a local start-up in order to ensure long-term use of this method, if its effectiveness, safety and acceptability are confirmed.

The OpTIS project in Saint-Joseph is thus a large-scale trial to suppress Aedes albopictus using boosted SIT under operational conditions. In addition to entomological and environmental indicators, it will take account of epidemiological indicators of dengue and chikungunya virus transmission, as well as psychometric indicators (measuring perceived exposure to mosquitoes and the acceptability of boosted SIT). The first survey on public perception and serological prevalence was conducted with support from IPSOS in July and August 2025.

In accordance with a prefectoral order (issued on 4 April 2025), the trials will run for 18 months and consist of two phases:

1. First, releases over 6 months across 60 hectares, from August 2025 to February 2026, at a rate of 1 000 treated sterile males/hectare/week;
2. Then, releases over 12 months across 175 hectares, from March 2026 to February 2027, still at a rate of 1 000 treated sterile males/hectare/week