Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 121 (Suppl. 1) 2026
Research Articles
Wolbachia introgression in Rio de Janeiro remains at sub-optimal levels 30 months after its decline: challenges in the sustainability of wMel interventions for dengue control
1Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Mosquitos Transmissores de Hematozoários, Rio de Janeiro, RJ, Brasil
2Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Biologia de Tripanosomatídeos, Rio de Janeiro, RJ, Brasil
3Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Biologia, Controle e Vigilância de Insetos Vetores, Rio de Janeiro, RJ, Brasil
4University of Montpellier, Centre National de la Recherche Scientifique, Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs Écologie Génétique Évolution et Contrôle, Montpellier, France
5Fundação Oswaldo Cruz-Fiocruz, Instituto Aggeu Magalhães, Departamento de Entomologia e Bioinformática, Recife, PE, Brasil
6Bernhard Nocht Institute for Tropical Medicine, Department of Entomology and Arbovirology, Hamburg, Germany
7Universidade Federal de Santa Maria, Santa Maria, RS, Brasil
8The University of Melbourne, Bio21 Institute, School of BioSciences, Pest and Environmental Adaptation Research Group, Melbourne, Australia
9Fundação Oswaldo Cruz-Fiocruz, Programa de Computação Científica, Rio de Janeiro, RJ, Brasil
DOI: 10.1590/0074-02760250212
ABSTRACT
BACKGROUND The deployment of the Wolbachia wMel strain is currently underway in multiple dengue-endemic municipalities across Brazil. The efficacy of this strategy in Rio de Janeiro remains uncertain, primarily due to the difficulty in sustaining high wMel prevalence in regions previously subjected to large-scale releases. A key contributing factor was the routine rotation of insecticides within the framework of Integrated Vector Management (IVM), which led to the use of the larvicide Spinosad for Aedes control in urban areas. This compound was associated with a precipitous decline in Aedes aegypti mosquitoes, regardless of the wMel infection status. While wMel-uninfected population recovered within weeks, wMel-infected population remained at low levels likely due to the fitness costs imposed by wMel on egg viability.
OBJECTIVES and METHODS Evaluate the updated frequency of Wolbachia wMel strain in neighborhoods that received deployments. Fort that, we assessed the long-term persistence of wMel following its demographic collapse, by performing mosquito sampling across 12 neighbourhoods in Rio de Janeiro, 30 months after mosquito populations crashed.
FINDINGS Our findings reveal that wMel introgression remains suboptimal, with a mean frequency of 9.87% across the sampled areas. Only two neighbourhoods exhibited wMel frequencies exceeding 15%, likely reflecting ongoing localised releases.
MAIN CONCLUSIONS The reduced prevalence underscores the challenges of achieving self-sustaining wMel establishment in complex urban environments and highlight critical considerations for the implementation of Wolbachia-based dengue control programs in endemic regions.
key words:
Aedes aegypti
Wolbachia
wMel
arboviruses control
dengue
insecticide resistance
integrative vector management
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Financial support: CNPq (312282/2022-2, 307209/2023-7), FAPERJ (E-26/211.159/2019, E-26/204.108/2024, E26/2001.844/2017, E-26/210.335/2022, E-26/210.537/2024).
KPP, GAG and RTF contributed equally to this work.
+ Corresponding author: freitas@ioc.fiocruz.br | 
https://orcid.org/0000-0002-2198-6492
Received 15 August 2025
Accepted 05 May 2026
HOW TO CITE
Padilha KP, Garcia GA, Teles-de-Freitas R, Gnonhoue FJ, David MR, Corrêa-Antônio J, et al. Wolbachia introgression in Rio de Janeiro remains at sub-optimal levels 30 months after its decline: challenges in the sustainability of wMel interventions for dengue control. Mem Inst Oswaldo Cruz. 2026; 121: e210212.
Handling editor: Adeilton Alves Brandão | https://orcid.org/0000-0001-5877-607X
