Dengue mosquitoes can be tamed by common microbes

Adiutarini had the first of two dengue attacks in 1986, when she was still a medical student. Within hours, her temperature soared to 104 degrees Fahrenheit and her knees were so trembling that she couldn’t stand up. Within a few days she was hospitalized. The experience is common in Yogyakarta, Indonesia, the hometown of Utarini. World’s highest dengue fever rate“Here, when you ask if you know someone who has had dengue fever, you can always name someone,” says Utarini, now a professor of public health at Gadjah Mada University.

Thanks to her work, that may change soon.

Dengue is caused by the virus, infecting an estimated 390 million people each year and killing about 25,000. The World Health Organization describes it as one of the top 10 threats to global health. It spreads when bitten by mosquitoes, especially mosquitoes. Aedes aegyptiUtarini and her colleagues have spent the last decade transforming these insects from dengue highways to dead ends.They are mosquitoes Wolbachia, Infected with dengue virus.. Wolbachia Spreads very quickly. If a small number of vector mosquitoes are released into the neighborhood, most of the insects in the area should be released from dengue within a few months. It’s as if Utarini’s team vaccinated several people with the disease and soon afterwards the entire population gained herd immunity.

The World Mosquito Program (WMP), a non-profit organization that developed this method, Small pilot study in Australia It was suggested It may work. Utarini, co-leader of WMP Yogyakarta, To do. Her team has been released Wolbachia–Carry mosquitoes in parts of Yogyakarta as part of a randomized controlled trial. The results announced last year and Now published, Showed that Wolbachia It spread rapidly among local mosquitoes, reducing the incidence of dengue fever by 77%. “This provides the gold standard of evidence. Wolbachia Is a very effective intervention for dengue, “said Oliver Brady, a dengue expert at the London School of Economics and Tropical Medicine. “It could revolutionize mosquito control.”

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The results of the test are very promising, and the researchers then Wolbachia――Mosquitoes inhabit the entire central part of Yogyakarta, a 32 square kilometer zone with more than 400,000 people. They are now expanding into the most populous states in the area, aiming to protect 4 million people by the end of 2022. Being optimistic, the team is boldly thinking about a bigger goal: completely eliminating dengue from the city.

“Dengue is a particularly troublesome virus,” said Natalie Dean, a statistician at the University of Florida.Come in 4 different versions, or “serotypes”. A person who recovers from one serotype can be infected with the other three serotypes.If that happens, they Likely to develop severe, potentially fatal symptomsTherefore, the only dengue vaccine in existence also increases the risk of severe dengue in people who have never been infected. Recommended only for those who have already encountered the disease..

Then there are mosquitoes. Aedes aegypti Once a forest bug Limited to sub-Saharan Africa, it sucked the blood of various animals. But at some point, some strains have evolved into urban creatures that prefer towns to forests and humans to other animals. Travel around the world on a slave ship, Aedes aegypti Prospered. There is no doubt that it is currently the most efficient human hunter on the planet. The feeling is in sharp harmony Carbon dioxide during breathing, warmth of the body, odor of the skin. Viruses such as Zika, Chikungunya, yellow fever, and dengue-causing viruses are also breeding. (Malaria, the most deadly mosquito disease, is caused by parasites spread by other species of mosquitoes.) “Dengue fever is one of the few infectious diseases that has increased year by year over the last few decades.” Said Brady. Aedes aegypti Insecticides can be poisoned, but resistance develops quickly. The stagnant water in which mosquitoes breed can be removed, but mosquitoes will always return. The world needed something new.

Wolbachia It was first discovered in 1924 in different species of mosquitoes. At first, it seemed so unobtrusive that scientists had ignored it for decades. But since the early 1980s, they have realized that this has extraordinary diffusion knack. It is mainly transmitted from the mother of the insect to the child and uses many tricks to ensure that the infected individual is more fertile than the uninfected individual.Until today, it’s at least 40% of all insect species, Has become one of the most successful microorganisms on the planet.

But Aedes aegypti Neither of WolbachiaNatural host. Scott O’Neill, the founder of WMP, spent decades ensuring that the latter was a stable infection of the former, and his team Finally successful in 2006Five years later, we released 300,000 special mosquitoes in two suburbs of Cairns, Australia. Within 4 months, 80-90% of local mosquitoes WolbachiaThe number of people infected with dengue fever has decreased, but it cannot be said whether it is due to mosquitoes or other factors.To prove it Wolbachia The team had to set up a randomized controlled trial because it could have a significant impact on dengue fever. I did that in Yogyakarta..

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First, WMP’s Indonesian branch spent years gaining public trust.Is Wolbachia This approach is unconventional, releasing live mosquitoes into the backyard of the house. In addition to setting up community meetings and WhatsApp hotlines, Utarini told me, “We have set up an entomology lab to allow people to see the technology for themselves.” By the time researchers began testing in 2017, their research showed that the attempt was endorsed by 88 percent of the general public. The team released most of the city in 24 zones. .. Wolbachia-Mosquitoes infected with half of them. About 10,000 volunteers I helped distribute a container of eggs to my local backyard. Within a year, about 95 percent Aedes Hiding mosquitoes in 12 release zones Wolbachia..

Since January 2018, the team has checked people in the city who came to the primary care clinic for fever and tested for dengue fever. This continued until March 2020, when the pandemic ended the trial prematurely, but fortunately it did not reach enough participants.The research team found that only 2.3% of people with heat stroke Wolbachia Dengue fever was generated in the release zone, but it was 9.4% in the control area. Wolbachia It also appeared to be effective against all four dengue serotypes, reducing hospitalizations for dengue by 86%.

Still, these already notable numbers can be underestimated. Mosquitoes move around, Wolbachia In 12 control zones where mosquitoes were not released. And people also move. Wolbachia It releases the zone, but is bitten and infected with dengue elsewhere. Both of these factors would have adversely affected the trial and weakened the results. The existence of these results is surprising, much less surprising. “There is no solid evidence that it is most effective. [dengue] There is intervention, “says Gonzalo Vásquez Prokopek of Emory University. He is studying vector-borne illnesses.” How many dengue patients look at the pesticide-spraying trucks? I don’t know if I can prevent it. “

Is Wolbachia The method has some restrictions. The bacterium takes months to settle and cannot be “deployed to contain today’s epidemic,” Basquez Prokopek said. As the Yogyakarta trial showed, it only works if: Wolbachia It reaches a prevalence of at least 80%. This requires a lot of work and strong community support. And the dengue virus can eventually evolve some resistance method. WolbachiaStill, Wolbachia Seems to block dengue infection In different waysIt defeats the virus in search of the nutrients it needs to propagate and strengthens the mosquito’s immune system. This should make it harder for the virus to circumvent it. Wolbachia Blockade.

Read: Decades of quest to build virus-resistant mosquitoes

There are other benefits to this method.It is self-amplifying and self-permanent: if enough Wolbachia-Infected mosquitoes should be released first, and bacteria should naturally dominate the population of the area and maintain its condition. Unlike pesticides Wolbachia It is very cost-effective because it is non-toxic, does not kill beneficial insects (or mosquitoes), and does not need to be reapplied. An analysis by Brady’s team showed that: You can actually save money by preventing infection..

“There is no reason to believe that the public health benefits seen in Yogyakarta will not occur elsewhere,” Anders said. “Science is there” WMP currently operates in 11 countries and territories. To date, 7 million people have lived under protective blankets. WolbachiaThe organization’s goal is to cover at least 75 million people by 2025 and at least 500 million people by 2030. These people are not protected by dengue fever alone. Wolbachia It seems to work for other illnesses Aedes aegypti Includes Zika and yellow fever. It can turn this mosquito from one of the most dangerous species to humans to another stinging annoyance.