Breakthrough dengue-prevention strategy passes huge trial

Infecting mosquitoes with a specific species of bacteria can shield them from dengue viruses, and as the bacteria spread to more mosquitoes, fewer and fewer can transmit dengue to humans.

Developed by the nonprofit World Mosquito Program (WMP), this breakthrough strategy to prevent dengue fever just passed a large clinical trial in Yogyakarta, Indonesia, The Atlantic reported. The trial showed how infecting mosquitoes with Wolbachia bacteria could reduce the incidence of dengue fever by about 77% in treated regions of the city, according to a report published Thursday (June 10) in The New England Journal of Medicine.

“That provides the gold standard of evidence that Wolbachia is a highly effective intervention against dengue,” Oliver Brady, a dengue expert at the London School of Hygiene and Tropical Medicine, who was not involved in the study, told The Atlantic. “It has the potential to revolutionize mosquito control.”

For the trial, the team divided a 10-square-mile (26 square kilometer) area of Yogyakarta into 24 clusters and released containers of bacteria-laden mosquito eggs into half of the clusters, Science Magazine reported. They added more eggs to the clusters every two weeks for 18 to 28 weeks. Ten months following the start of the releases, after the bacteria began spreading to local mosquito populations, the prevalence of bacteria in mosquitoes in the 12 treated clusters ramped up to 80% or higher.

The bacteria itself is a species called Wolbachia pipientis, which scientists have known naturally infects many insects and can block dengue viruses from replicating, The Atlantic reported. However, the bacteria doesn’t usually infect Aedes aegypti mosquitoes, the main transmitters of dengue. It took about a decade of work, but scientists finally figured out how to get a specific strain of the bacteria, called wMel, to survive and multiply in A. aegypti eggs. Once born, the resulting mosquitoes still carry the bacteria.

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As Wolbachia bacteria rapidly spread among mosquitoes, the rate of new dengue fever cases plummeted among Yogyakarta residents, the trial organizers found. The team had recruited study participants and monitored them for new cases of fever; of those with fevers, only 2.3% tested positive for dengue virus in treated clusters, as compared with 9.4% of those from control areas, Science reported. That represents a 77% reduction in infections. 

In addition, the treatment was also linked to an 86% reduction in hospitalizations for dengue fever. “That’s really the big thing,” Cameron Simmons, an infectious disease researcher at Monash University, Melbourne, and an investigator with WMP, which conducted the new study, told Science. “It’s the weight of hospitalization … that really stretches health systems.”

The trial conductors are now releasing more mosquitoes into densely populated regions of Yogyakarta that weren’t included in the trial. If they can cover their targeted areas by 2022, as planned, their efforts should prevent 10,000 dengue infections each year, Katherine Anders of the WMP told The Atlantic.

Read more about the trial in The Atlantic and Science.

Originally published on Live Science.

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