Fighting the tiger beetle, a bacterium reduces reproductive capacity by 90 percent

Italian researchers have made a breakthrough in the fight against the tiger mosquito, with a new method reducing its reproductive capacity by up to 90 percent. The approach involves releasing genetically modified male mosquitoes infected with the bacterium Wolbachia, which renders them incompatible with wild female mosquitoes. This technique was tested on a large scale for the first time in Europe through a pilot campaign conducted at the Enea Research Centre in Casaccia near Rome. The project involved the release of approximately 1.6 million specially engineered male mosquitoes, designed to lower the fertility rate of the species without harming the environment. The experiment, carried out in collaboration between Enea, Google LLC, and Sapienza University of Rome, aimed to develop a sustainable alternative to chemical insecticides used to control the tiger mosquito (Aedes albopictus). This species is known not only for being a nuisance during summer months but also for transmitting diseases such as dengue, chikungunya, and Zika, which have increasingly affected parts of Europe. By introducing these modified males into the population, the scientists were able to significantly reduce the number of viable eggs produced by wild females, effectively curbing the mosquito population over time. At the heart of this strategy lies the Wolbachia bacterium, which is commonly found in many insect species. When present in both male and female mosquitoes, Wolbachia enables successful reproduction. However, when the bacterium is introduced into male mosquitoes, it causes the females they mate with to become sterile. Researchers at Enea replaced the native Wolbachia strain in tiger mosquitoes with one typically found in common mosquitoes. This change created a biological mechanism that ensures the majority of offspring produced by wild females are infertile, thus reducing the overall mosquito population sustainably. Google played a key role in scaling up the production of these modified mosquitoes. The company developed methods to multiply the population of tiger mosquitoes carrying the Wolbachia bacteria, selected only the male individuals, and arranged their transport via air from Miami, United States, to the release site in Casaccia. This logistical effort allowed for the controlled distribution of millions of mosquitoes within the designated area. The pilot program took place over a period of five months, from late July to late October 2025, within a 53-hectare area on the grounds of the Enea Research Centre in Casaccia. During this time, around 1.6 million incompatible male mosquitoes were released. The research continues into the current year, with ongoing monitoring and evaluation of the results. According to Maurizio Calvitti, a researcher at Enea’s Sustainable Agri-Food Systems Division, the Casaccia centre serves as a prototype for future mosquito control strategies that could be implemented in other regions facing similar challenges. Sapienza University of Rome contributed to the project by validating the effectiveness of the technique and monitoring areas that were not treated with the method. Their involvement ensured that the data collected was reliable and comparable, allowing researchers to assess the impact of the intervention accurately. The university's expertise in studying disease-carrying insects helped refine the methodology and improve the precision of the results obtained. The success of this pilot program has raised interest among public health officials and environmental experts looking for long-term solutions to mosquito-borne illnesses. Unlike traditional insecticides, which can harm non-target species and lead to resistance over time, this biological method offers a more targeted and environmentally friendly approach. Scientists emphasize that while the technique is currently focused on tiger mosquitoes, it could potentially be adapted to combat other mosquito species responsible for spreading diseases in different parts of the world. Researchers continue to analyze the data gathered from the pilot study, aiming to understand the long-term effects of the method on mosquito populations and the surrounding ecosystem. They are also exploring ways to optimize the process, including improving the efficiency of mosquito breeding and transportation. As the findings emerge, they will inform future strategies for controlling mosquito populations in urban and rural settings alike.