The impact of large-scale release of <i>Wolbachia</i> mosquitoes on dengue incidence in Campo Grande, Brazil: an ecological study.

Abstract

<h4>Background</h4>The introduction of the <i>w</i>Mel strain of <i>Wolbachia</i> into <i>Aedes aegypti</i> mosquitoes significantly reduces dengue virus transmission. We evaluated the impact of large-scale releases of <i>Wolbachia</i>-infected <i>Ae. aegypti</i> on dengue incidence in Campo Grande, a large urban city in the Central-West region of Brazil, in the first deployment of <i>Wolbachia</i> as an official dengue-control strategy by the Brazilian federal government.<h4>Methods</h4>Mosquitoes infected with <i>w</i>Mel <i>Wolbachia</i> were released in geographically phased deployments throughout Campo Grande from December 2020 through December 2023. An ovitrap surveillance network monitored <i>Wolbachia</i> prevalence in local <i>Ae. aegypti</i> populations during and after releases. Mixed-effects negative binomial regression was used to evaluate neighborhood-level monthly notified dengue incidence (2008-2024) as a function of monthly <i>w</i>Mel exposure status, comparing fully treated (<i>w</i>Mel prevalence stably ≥60%) and partially treated (ongoing releases or <i>w</i>Mel <60%) with untreated periods, accounting for seasonal variation.<h4>Findings</h4>More than 100 million <i>Wolbachia</i>-infected mosquitoes were released, achieving a post-intervention mean <i>Wolbachia</i> prevalence of 86.4% (95% CI 84.0-88.9), with 89% of intervention areas reaching stable <i>Wolbachia</i> levels ≥60%. Stable establishment of <i>w</i>Mel at ≥60% prevalence was associated with a 63.2% (95% CI 51.9-71.9) reduction in dengue incidence.<h4>Interpretation</h4>Our results demonstrate successful large-scale <i>Wolbachia</i> establishment in <i>Ae. aegypti</i> populations and a substantial epidemiological impact on dengue incidence in an urban Brazilian setting. This study provides robust evidence supporting <i>Wolbachia</i> deployment as an effective, sustainable public health intervention and validates its implementation as a federal government-supported dengue control strategy in Brazil.<h4>Funding</h4>This work was supported by the Brazilian Ministry of Health and the Oswaldo Cruz Foundation.