Brive in France Tests Sterile Insect Technique Using X-Ray Irradiation to Control Tiger Mosquitoes, Preliminary Results Show Nearly 60% Sterility Rate in Mosquito Eggs

The city of Brive-la-Gaillarde in the Nouvelle-Aquitaine region of France is using the Sterile Insect Technique (SIT) to control tiger mosquitoes. Since May 2025, the city has been working with the Montpellier-based company Terratis, releasing male mosquitoes that have been treated with X-ray irradiation and rendered incapable of reproduction, in order to reduce the tiger mosquito population.

The core of this method is to allow sterile males to mate with wild females, causing the females to lay eggs that cannot hatch. Although it may appear that mosquitoes are still being released in active mosquito areas, the released individuals are males, which do not bite humans.

As of October 31, 2025, Brive has deployed nearly 11 million sterile male mosquitoes across 58 release points covering more than 100 hectares, with a weekly release volume of approximately 400,000. Scientific monitoring is conducted through 37 oviposition traps installed in protected zones, buffer zones, and control zones, with weekly counts of mosquito eggs and assessments of sterility rates.

Terratis reports that first-year results show that in areas with the highest tiger mosquito density, the peak mosquito population was suppressed as early as June; after one year of implementation, the egg sterility rate approached 60%. The company believes that the effects of this type of technology will become apparent gradually, and the releases carried out before the end of October 2025 will also reduce the number of hatchable mosquito eggs in the spring of 2026.

Based on the preliminary results, the city of Brive has decided to continue the project, with the goal of achieving a 90% control indicator in residential areas by 2026. Full results are expected to be published in October.

The town of Sainte-Eulalie in the Gironde department of France also partnered with Terratis in July of this year to implement the same Sterile Insect Technique for tiger mosquito control. Local scientific monitoring is still ongoing, and the relevant results will be further announced at the end of the season.