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ABSTRACT
Background
Releases of Wolbachia (wMel)-infected Aedes aegypti mosquitoes significantly reduced the incidence of virologically confirmed dengue in a previous cluster randomised trial in Yogyakarta City, Indonesia. Following the trial, wMel releases were extended to the untreated control areas, to achieve city-wide coverage of Wolbachia.
Objective
In this predefined analysis, we evaluated the impact of the wMel deployments in Yogyakarta on dengue hemorrhagic fever (DHF) case notifications and on the frequency of perifocal insecticide spraying by public health teams.
Methods
Monthly counts of DHF cases notified to the Yogyakarta District Health Office between January 2006 and May 2022 were modelled as a function of time-varying local wMel treatment status (fully- and partially-treated vs untreated, and by quintile of wMel prevalence). The frequency of insecticide fogging in wMel-treated and untreated areas was analysed using negative binomial regression.
Results
Notified DHF incidence was 83% lower in fully treated vs untreated periods (IRR 0.17 [95% CI 0.14, 0.20]), and 78% lower in areas with 80–100% wMel prevalence compared to areas with 0–20% wMel (IRR 0.23 [0.17, 0.30]). A similar intervention effect was observed at 60–80% wMel prevalence as at 80–100% prevalence (76% vs 78% efficacy, respectively). Pre-intervention, insecticide fogging occurred at similar frequencies in areas later randomised to wMel-treated and untreated arms of the trial. After wMel deployment, fogging occurred significantly less frequently in treated areas (IRR 0.17 [0.10, 0.30]).
Conclusions
Deployments of wMel-infected Aedes aegypti mosquitoes resulted in an 83% reduction in the application of perifocal insecticide spraying, consistent with lower dengue case notifications in wMel-treated areas. These results show that the Wolbachia intervention effect demonstrated previously in a cluster randomised trial was also measurable from routine surveillance data.
Responsible Editor
Stig Wall
Responsible Editor
Stig Wall
Acknowledgment
We are grateful to all the World Mosquito Program staff in Yogyakarta and in WMP Global who contributed to this study and to the people of Yogyakarta for their cooperation and support. We acknowledge the collaboration of the Yogyakarta District Health Office in supporting this work. We acknowledge the support of Jai Denton in data visualisation.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Author contributions
All authors reviewed and agreed upon the final manuscript. CI contributed to study conceptualisation, investigation, data collection, and revision of the final manuscript. SKT contributed to study conceptualisation, analysis, writing of the original draft, and revision of the final manuscript. UK, MRA and R contributed to investigation and data collection. WT contributed to study conceptualisation, investigation and data collection. RAA contributed to study conceptualisation and investigation. SMD and NPJ contributed to analysis and revision of the final manuscript. AU contributed to study conceptualisation, funding acquisition, project administration and revision of the final manuscript. CPS contributed to study conceptualisation and revision of the final manuscript. KLA contributed to study conceptualisation, analysis, writing of the original draft, and revision of the final manuscript.
Ethics and consent
The AWED trial was conducted in accordance with the International Council for Harmonisation guidelines for Good Clinical Practice and was approved by the human research ethics committees at Universitas Gadjah Mada and Monash University.
Paper context
A cluster randomised trial of Wolbachia-infected mosquito releases previously demonstrated the efficacy of this innovative method for dengue control in Yogyakarta, Indonesia. In this predefined secondary analysis of that trial, we show that the efficacy of Wolbachia was measurable also from time-series analysis of routine dengue surveillance data and that the intervention substantially reduced the frequency of insecticide fogging by public health teams. This highlights the broader benefits of applying Wolbachia for dengue control.
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/16549716.2023.2166650