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Updated: Sep 12, 2026
Maintaining Aedes aegypti Mosquitoes Infected with Wolbachia
Published on: August 14, 2017
Impact of Wolbachia-mediated incompatible and sterile insect techniques on dengue incidence: a large-scale cluster
Chia-Chen Chang1, Jue Tao Lim2, Chee Seng Chong3
1Environmental Health Institute, National Environment Agency, Singapore; Department of Biological Sciences, National University of Singapore, Singapore.
Background:
Wild-type female Aedes aegypti which mate with Wolbachia-infected male Aedes aegypti (Wolbachia-Aedes) produce non-viable eggs due to cytoplasmic incompatibility. Sustained releases of Wolbachia-infected male Aedes aegypti can suppress wild-type mosquito populations, but robust evidence of its efficacy in reducing dengue incidence is needed.
Methods:
We conducted a large-scale cluster-randomised controlled trial involving releases of male wAlbB-infected Ae. aegypti mosquitoes (wAlbB-SG) for dengue control in Singapore. Mosquitoes were irradiated to sterilise potential residual females. Fifteen clusters were randomised: 8 clusters received deployments of male wAlbB-SG infected Ae. aegypti (intervention clusters, n = 393,236) and 7 clusters received no deployments (control clusters, n = 331,192). All clusters practised baseline vector control measures. We assessed the protective efficacy of Wolbachia-Aedes to reduce dengue incidence using a differences-in-differences framework. The trial was registered with ClinicalTrials.gov (Identifier: NCT05505682) on 2022-08-18.
Findings:
In the pre-intervention period, dengue incidence per 100,000 was similar across control (18.63) and intervention (18.14) arms. During the intervention period, reported dengue incidence was 11.31 and 36.57 cases per 100,000 residents in intervention and control arms, respectively. Six months after releases began, intervention clusters showed reductions in total dengue incidence, ranging from 27.6% (95% CI: -35.4% to 61.3%) to 83.8% (95% CI: 50.4%-94.7%). This protective effect varied across time, with some attenuation observed during the 2023 inter-epidemic period. We estimated that 2351 cases (95% CI: 1968-2735) were averted over the period of the trial, relative to 1037 dengue cases reported in the intervention arm. Reductions in epidemiologically-linked dengue incidence were greater, ranging from 60.9% (95% CI: 21.3%-80.6%) to 99.8% (95% CI: 99.2%-99.9%).
Interpretation:
Our results demonstrate the high efficacy of Wolbachia-Aedes in reducing dengue incidence.
Funding:
Ministry of Finance, Singapore.
