Journal Article

The long-term persistence of the wMel strain in Rio de Janeiro is threatened by poor integrated vector management and bacterium fitness cost on Aedes aegypti

Lima, José Bento Pereira, Villela, Daniel Antunes Maciel, Dias, Luciana, Maciel-de-Freitas, Rafael, Brito, Luiz Paulo, Pavan, Márcio Galvão, Hoffmann, Ary, Cruz, Oswaldo Gonçalves, Garcia, Gabriela Azambuja, Martins, Ademir Jesus, Gnonhoue, Franck Jeannot, Corrêa-Antônio, Jessica, Padilha, Karine Pedreira, Wallau, Gabriel Luz, Corbel, Vincent, de Oliveira, Felipe

2025

Overview

New tools and methods are currently under evaluation by the World Health Organization for preventing arbovirus transmission, such as dengue, Zika, and chikungunya. One promising approach involves deploying Aedes aegypti with the endosymbiotic bacterium Wolbachia pipientis to disrupt arbovirus transmission within endemic urban environments. The release program of mosquitoes with the Wolbachia ’s w Mel strain started in August 2017 in 6.88% of the city area of Rio de Janeiro, where 13.1% of the city’s population live (~890,000 inhabitants). The deployment of Wolbachia w Mel strain in Rio finished in December 2019 with a suboptimal 32% introgression of w Mel strain, which coincided with a 38% and 10% reduction of dengue and chikungunya, respectively. We conducted an independent evaluation during 20 consecutive months to evaluate whether the w Mel distribution and frequency would expand or retract. More than 50,000 mosquitoes were sampled in 12 neighborhoods with estimated 500,000 inhabitants, of which 39.2% were Ae. aegypti . In total, 7,613 of 19,427 collected Ae. aegypti were screened individually for w Mel. Climate, environmental and insecticide application data was used to model the spatiotemporal introgression of w Mel. The routine insecticide rotation adopted by the Brazilian Ministry of Health caused the crash of both w Mel-infected and -uninfected populations shortly after an increase in coverage with spinosad. However, the w Mel-uninfected mosquitoes recovered soon to levels even higher than before, whereas the w Mel-infected failed to recover after the population crash. The well documented fitness cost of w Mel in egg hatching leads to the absence of an egg bank necessary to recover after adult population was disrupted. Finally, we observed the mtDNA haplotype associated with released Wolbachia at a frequency of ~25% in field-caught uninfected mosquitoes. The reason underlying the poor introgression of Wolbachia w Mel strain is multifold. The adoption of an effective larvicide that crashed both w Mel-infected and -uninfected populations, the absence of an egg bank due to high fitness cost of egg hatching in the w Mel-infected mosquitoes, a suboptimal Wolbachia invasion before the intervention, and Wolbachia loss synergically contributed to the lower invasion and, by corollary, modest epidemiological outcome in Rio de Janeiro. Our results highlight the need to plan and implement technical guidance on Integrated Vector Management in Brazil prior and during the nationwide release of Wolbachia -infected mosquitoes to optimize dengue mitigation efforts while ensuring the judicious use of resources.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Aedes - microbiology / Aedes - virology / Animals / Biology and Life Sciences / Brazil / Dengue - prevention & control / Dengue - transmission / Female / Genetic Fitness / Humans / Medicine and Health Sciences / Mosquito Control - methods / Mosquito Vectors - microbiology / Mosquito Vectors - virology / People and places / Pest Control, Biological - methods / Wolbachia - genetics / Wolbachia - physiology