How Wolbachia Stops Dengue In Its Tracks

Scientists have shown that infecting mosquitoes with Wolbachia bacteria prevents them from carrying dengue and lowers disease incidence by 77 percent.

AsianScientist (Jun. 17, 2021) – For the first time, scientists have conclusively shown through a randomized controlled trial that deliberately loading mosquitoes with a virus-blocking microbe can protect them—and humans—against dengue infection. Their findings were described in The New England Journal of Medicine.

Considered by the World Health Organization as one of the top ten threats to global health, the mosquito-borne dengue virus infects an estimated 390 million people annually—with Southeast Asia racking up the greatest number of deaths attributed to dengue.

Dengue’s wide reach can be credited to its carrier, the ever-present Aedes aegypti mosquito. With their insatiable taste for human blood, these hardy pests thrive in warm, tropical climates and prefer to breed in stagnant water found in and around our homes. However, efforts to control A. aegypti through insecticides or environmental management methods have so far been ineffective worldwide.

With the help of a surprisingly common bacteria called Wolbachia, researchers from the World Mosquito Program (WMP) are converting these very carriers into weapons against the virus. As viruses like dengue cannot reproduce on their own, they need to infiltrate the cells of carriers like A. aegypti to proliferate and spread.

But when Wolbachia stakes its claim on the mosquito, the dengue virus is left with little resources to hijack for its survival. Once established, the bacteria doesn’t budge, spreading quickly throughout the mosquito population and making all the local insects dengue-free within a few months.

Led by Gadjah Mada University Professor Adi Utarini, WMP’s Yogyakarta chapter released Wolbachia-infected mosquitoes into selected clusters as part of a randomized controlled trial—the gold standard for evaluating the effectiveness of interventions.

For the trial, the team divided a 26 km2 area in Yogyakarta into 24 clusters. In half of these clusters, the team discretely placed containers of Wolbachia-carrying mosquito eggs in residential properties every two weeks for up to seven months. Incredibly, not only did the incidence of dengue fever drop by 77 percent in the treated clusters, but so did the number of dengue patients requiring hospitalization by 86 percent.

While the method previously worked in smaller pilot studies in Australia, the project in Yogyakarta represents the first large-scale trial to compare dengue incidence in clusters with and without Wolbachia-infected mosquitoes.

Similar to how clinical trials test the therapy along with a placebo, running the randomized controlled trial conclusively proved the bacteria’s ability to stop dengue in its tracks. Besides dengue, Wolbachia may soon similarly protect against other viruses carried by A. aegypti—including yellow fever, chikungunya and Zika.

“Together with the results of the trial reported here, these data suggest that when [Wolbachia] is established at high prevalence in local A. aegypti populations, reductions in the incidence of dengue follow,” wrote the authors. “The approach of Wolbachia…represents a novel product class for the control of dengue.”

The article can be found at: Utarini et al. (2021) Efficacy of Wolbachia-infected mosquito deployments for the control of dengue.


Source: World Mosquito Program. Photo: Pexels.
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