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‘Revolutionary’ trial used mosquitoes infected with bacteria to eradicate dengue fever


Photo of Aedes aegypti mosquitoes infected with Wolbachia bacteria, taken at the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil on October 2, 2014.

A picture of Aedes aegypti mosquitoes infected with Wolbachia bacteria, taken at the Oswaldo Cruz Foundation in Rio de Janeiro, Brazil, on October 2, 2014.
Photo: Christophe Simon / AFP (Getty Images)

An unconventional ploy to tackle dengue fever in Indonesia appears to have gone incredibly well.

In a new study published this week, scientists report that cases of dengue fever, a deadly disease transmitted by mosquitoes, dramatically decreased in areas where they introduced mosquitoes intentionally infected with bacteria called Wolbachia. Bacteria are thought to avoid mosquitoes to get dengue fever in the first place. These results are the strongest evidence to date that Wolbachia can help eradicate dengue and other nasty infections spread by mosquitoes.

Over the past decades, dengue has become one of the most common infections in the world. Also known as shattering fever for the debilitating pain it can cause, the viral illness is valued infect up to 400 million people worldwide and make 100 million people sick every year. It can also rarely turn into a life-threatening infection that causes severe internal bleeding, called hemorrhagic fever.

Dengue’s track record has long made it an attractive target for research. In 2016, the very first the dengue vaccine has been approved, called Dengvaxia. But the vaccine is only moderately effective and not recommended for people who have never had dengue fever before, as this may increase the risk of serious illness if the person experiences dengue for the first time after vaccination (for people who have had dengue fever before, the vaccine helps to prevent serious). So there is still a need for better anti-dengue measures.

In recent years, some scientists have been working on another strategy, taken from nature itself. Many insects often carry Wolbachia, bacteria that need to live inside cells to survive. Wolbachiainteractions with its hosts can be incredibly complex and often symbiotic, to the point that the insects depend on them for their survival. Some mosquitoes, in particular Aedes aegypti, the main vector of dengue, are generally not carriers Wolbachia. But when they do, the bacteria render infected male mosquitoes unable to successfully breed with uninfected female mosquitoes; at the same time, the infection is transmitted to offspring. This knowledge led scientists to create a technical where the eggs of infected male mosquitoes are deposited in an area, mature into adults, and then try, without success, to breed with the local females, ultimately leading to population decline.

Othis groups tested a slightly different approach. Their research has shown that when you infect Ae. Egypt mosquitoes with a Wolbachia strain, an extracted from fruit flies, they become much less able to catch and transmit dengue. These mosquitoes also spread Wolbachia to the next generation, ensuring that the bacteria continue to act as a dengue deterrent, without needing to go through the long process of trying to destroy the premises mosquito population.

Studies of this method have been underway since 2011, including in parts of the United States, led by the World Mosquito Program (WMP). These studies suggested that the strategy could be successful without causing negative impacts on people or wildlife. But the group’s latest study, a three-year study randomized controlled trial published in the New England Journal of Medicine at Wednesday is their biggest test yet, and it seems to have passed with flying colors.

The study involved around 8,000 residents living in Yogyakarta, Indonesia, where dengue is endemic. Their quarters were divided into 24 clusters, and the team’s infected mosquito eggs were deployed in half of those areas, while the native skeeter population was left alone in the other half. In areas where infected mosquitoes have been planted, cases of confirmed dengue fever fell 77% during the study period, compared to control neighborhoods. Dengue-related hospitalizations also fell by 86% in the experimental areas.

“This test result shows the significant impact of Wolbachia method may have to reduce dengue fever in urban populations. This result demonstrates how an exciting breakthrough Wolbachia may be-a new class of safe, durable and effective dengue control products is exactly what the global community needs, ”said co-lead author Cameron Simmons of Monash University in a commentary. declaration of the WMP.

The results of this type of clinical trial, often considered the gold standard for proving that a treatment works, are likely to lead to much greater acceptance of its use. The WMP has already committed to treating the rest of Yogyakarta, and they hope to expand their project to reach areas covering as many half a billion people at risk of dengue over the next decade, with approval of governments and residents, Nature News reported Last year. In the best-case scenario, this technique coupled with others could one day lead to the total eradication of dengue, as well as other viruses transmitted by mosquitoes such as Zika and chikungunya.

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