A study conducted by Fiocruz, the universities of Yale, Stanford, Johns Hopkins, São Paulo (USP) and Monash University (Australia), by the World Mosquito Program (WMP) and the Municipal Health Department of the City of Campo Grande and the State Health Department of Mato Grosso do Sul presents a detailed analysis of the mass release of Aedes aegypti mosquitoes with Wolbachia bacteria as a dengue fever control strategy in Campo Grande (MS). The results indicate a 63.2% reduction in cases, in 2024, in areas where Wolbachia reached stable levels in the mosquito population, after the intervention carried out between 2020 and 2023.

With the participation of Fiocruz Mato Grosso do Sul and Fiocruz Minas, the research will be published in the February 2026 issue of The Lancet Regional Health - Americas, and evaluated the intervention as a public policy funded and coordinated by the Brazilian Ministry of Health, marking the first scientific analysis of this type of program nationally.

The release of mosquitoes with Wolbachia was done continuously for three years, covering six major urban areas with over 100 million insects released. The technique involves introducing the Wolbachia bacterium (common in around 60% of insects) into the mosquito Aedes aegypti. The bacterium prevents viruses from multiplying inside the mosquito, diminishing its ability to transmit diseases. In 2024, Campo Grande had an average prevalence of 86.4% of the bacteria in mosquitoes and 89% of the monitored areas reached a prevalence equal to or greater than the 60% threshold, considered an indicator of stability. Entomological monitoring used 1,677 ovitraps (mosquito egg traps) spread throughout the city, which enabled the monitoring of Wolbachia monthly progress.

Analysis of the historical series of dengue fever cases (2008-2024) shows that, after the intervention, the city no longer recorded outbreaks as severe as those observed in the pre-Wolbachia period. Before implementation, annual cases often exceeded 4,700 records. After the release of bacteria-infected mosquitoes, the city registered 410 cases in 2021, 8,045 in 2022, 11,406 in 2023 and 605 until September 2024. The study also shows an even relation between the prevalence of Wolbachia and the drop in disease cases: the higher the percentage of bacteria-infected mosquitoes, the lower the number of dengue fever cases.

The article highlights that the strategy is integrated into regular health surveillance actions, makes no use of chemicals and transitions into autonomous maintenance of the mosquito population over time. He also emphasizes that Wolbachia is added to other prevention initiatives, such as eradicating breeding sites and vaccination, comprising a set of measures to reduce the transmission of arboviruses.

The implementation of the Wolbachia Method in Brazil is the subject of an episode of the Fiotec Apoia series, available on the institution's YouTube channel.

Fiocruz Mato Grosso do Sul played a key role in the local conduction of the study, coordinating scientific production and epidemiological monitoring. The Secretariat of the Campo Grande Municipal Health Department was directly involved in the territorial logistics and operationalization of the strategy, ensuring continuity of field activities.

The State Department of Health supported the initiative by providing the building for the installation and maintenance of the mosquito production plant and providing two vehicles with fuel for the releases, in addition to three technicians for the project.

The study shows that the intervention is technically feasible, has consistent community adherence and epidemiological impact, characteristics that could support its expansion to other municipalities. In a national scenario with high transmission of arboviruses, these findings contribute to expanding evidence-based policies and developing integrated approaches to dengue fever surveillance and control.

The analysis also reinforces the importance of coordinated actions between research institutions, health systems and the community, contributing to the advancement of sustainable arbovirus control strategies in Brazil.

Source: Agência Fiocruz de Notícias (AFN).