Large-scale deployment and establishment ofWolbachiainto theAedes aegyptipopulation in Rio de Janeiro, Brazil

Abstract

Traditional methods of vector control have proven insufficient to reduce the alarming incidence of Dengue, Zika and chikungunya in endemic countries. The bacterium symbiont Wolbachia has emerged as an efficient pathogen-blocking and self-dispersing agent that reduces the vectorial potential of Aedes aegypti populations and potentially impairs arboviral disease transmission. In this work, we report the results of a large-scale Wolbachia intervention in Ilha do Governador, Rio de Janeiro, Brazil. wMel-infected adults were released across residential areas between August 2017 and March 2020. Over 131 weeks, including release and post-release phases, we monitored the wMel prevalence in field specimens, and analyzed introgression profiles of two assigned intervention areas, RJ1 and RJ2. Our results revealed that wMel successfully invaded both areas, reaching overall infection rates of 50-70% in RJ1, and 30-60% in RJ2 by the end of the monitoring period. At the neighborhood-level, wMel introgression was heterogeneous in both RJ1 and RJ2, with some profiles sustaining a consistent increase in infection rates and others failing to elicit the same. Correlation analysis revealed a weak overall association between RJ1 and RJ2 (r = 0.2849, P = 0.0236), and an association at a higher degree when comparing different deployment strategies, vehicle or backpack-assisted, within RJ1 (r = 0.4676, P < 0.0001) or RJ2 (r = 0.6263, P < 0.0001). The frequency knockdown resistance (kdr) alleles in wMel-infected specimens from both areas was consistently high over this study. Altogether, these findings corroborate that wMel can be successfully deployed at large-scale as part of vector control intervention strategies, and provide the basis for imminent disease impact studies in Southeastern Brazil.

A decade of stability for wMel Wolbachia in natural Aedes aegypti populations

“…Releases of wMel-infected Ae. aegypti have now been carried out in several dengue-endemic cities including Yogyakarta, Indonesia [18] and Rio de Janeiro [19,20] and Niterói [21,22], Brazil. Quasiexperimental and/or randomized controlled trials show that wMel releases have reduced dengue incidence by >69% [8,22,23], with reductions in chikungunya and Zika transmission also apparent in some locations [22].…”

“…Long-term monitoring shows that wMel has persisted in Ae. aegypti populations at high frequencies for many years [16,17,21], though in some locations the infection has remained at an intermediate frequency or dropped out, requiring supplemental releases [19,20,22]. wMel frequencies can also fluctuate seasonally, likely due to high temperatures experienced in larval habitats [24,25].…”