Imagine a way to fight dengue fever that doesn't involve spraying chemicals or just telling people to avoid bites. In Singapore, scientists tried something new: they released millions of male mosquitoes infected with a harmless bacteria called Wolbachia. When these males mate with wild female mosquitoes, the eggs don't hatch. Over time, this can shrink the local mosquito population. The trial involved over 720,000 people across 15 neighborhoods. Some areas got the special mosquito releases; others didn't. The results were striking. In the areas with the releases, the number of adult female mosquitoes—the ones that bite and spread dengue—dropped sharply. More importantly, far fewer people got sick. In those areas, only 6% of people tested for dengue-like symptoms actually had the virus, compared to 21% in the areas without the mosquito releases. The protection was strong and lasted. For people exposed to these mosquitoes for 3 to 12 months or more, their odds of getting a confirmed dengue infection were reduced by 71% to 72%. This trial shows that using these 'sterile' male mosquitoes can be a powerful tool to suppress mosquito populations and protect people from dengue.
Can releasing special male mosquitoes stop dengue? A trial in Singapore shows promising results.
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Releasing sterile, bacteria-infected male mosquitoes cut dengue infections by over 70% in a large Singapore trial. What this means for you:
Releasing sterile, bacteria-infected male mosquitoes cut dengue infections by over 70% in a large Singapore trial. View Original Abstract ↓
BACKGROUND: Wild-type female mosquitoes that mate with male mosquitoes that have been infected with the AlbB strain of bacteria produce nonviable offspring owing to cytoplasmic incompatibility. Repeated releases of wolbachia-infected males can potentially suppress wild-type mosquito populations and reduce the risk of dengue virus infection.
METHODS: We conducted a trial involving the release of male mosquitoes infected with the AlbB strain of wolbachia bacteria for the control of dengue in Singapore, a tropical city-state. In this cluster-randomized trial with test-negative controls, we divided 15 geographic population clusters into two groups: 8 clusters received deployments of male wolbachia-infected mosquitoes (intervention clusters) and 7 clusters received no deployments (control clusters). The primary end point was the diagnosis of symptomatic dengue virus infection of any severity caused by any serotype of the virus, as measured by the odds ratio for the distribution of wolbachia exposure among laboratory-confirmed reported dengue cases as compared with test-negative controls.
RESULTS: A total of 393,236 residents lived in the intervention clusters, and 331,192 lived in the control clusters. Adult wild-type populations were suppressed across the intervention clusters. The baseline average abundance of the mosquitoes (number of adult female mosquitoes trapped divided by number of traps) was 0.18 and 0.19 in the intervention and control clusters, respectively; from 3 months after the initiation of the intervention until the end of the 24-month trial period, the average abundance was 0.041 and 0.277, respectively. In the intention-to-treat analysis at 6 months or more, the percentage of residents in the intervention clusters who were dengue-positive was lower than that in the control clusters (354 of 5722 tests [6%] vs. 1519 of 7080 tests [21%]). The protective efficacy of the intervention, calculated as (1 - odds ratio) × 100, ranged from 71 to 72% with 3 to 12 months or more of wolbachia mosquito exposure, as represented by odds ratios of 0.28 to 0.29.
CONCLUSIONS: Release of sterile wolbachia-infected male mosquitoes reduced vector populations and the risk of dengue infection in Singapore. (Funded by the Singapore Ministry of Finance and others; ClinicalTrials.gov number, NCT05505682.).