Dengue Mosquitoes Can Be Tamed by a Common Microbe - The Atlantic - 0 views
-
Dengue fever is caused by a virus that infects an estimated 390 million people every year, and kills about 25,000; the World Health Organization has described it as one of the top 10 threats to global health.
-
It spreads through the bites of mosquitoes, particularly the species Aedes aegypti. Utarini and her colleagues have spent the past decade turning these insects from highways of dengue into cul-de-sacs. They’ve loaded the mosquitoes with a bacterium called Wolbachia, which prevents them from being infected by dengue viruses. Wolbachia spreads very quickly: If a small number of carrier mosquitoes are released into a neighborhood, almost all of the local insects should be dengue-free within a few months
-
Aedes aegypti was once a forest insect confined to sub-Saharan Africa, where it drank blood from a wide variety of animals. But at some point, one lineage evolved into an urban creature that prefers towns over forests, and humans over other animals.
- ...10 more annotations...
-
The World Mosquito Program (WMP), a nonprofit that pioneered this technique, had run small pilot studies in Australia that suggested it could work. Utarini, who co-leads WMP Yogyakarta, has now shown conclusively that it does.
-
Carried around the world aboard slave ships, Aedes aegypti has thrived. It is now arguably the most effective human-hunter on the planet, its senses acutely attuned to the carbon dioxide in our breath, the warmth of our bodies, and the odors of our skin.
-
Wolbachia was first discovered in 1924, in a different species of mosquito. At first, it seemed so unremarkable that scientists ignored it for decades. But starting in the 1980s, they realized that it has an extraordinary knack for spreading. It passes down mainly from insect mothers to their children, and it uses many tricks to ensure that infected individuals are better at reproducing than uninfected ones. To date, it exists in at least 40 percent of all insect species, making it one of the most successful microbes on the planet.
-
The team divided a large portion of the city into 24 zones and released Wolbachia-infected mosquitoes in half of them. Almost 10,000 volunteers helped distribute egg-filled containers to local backyards. Within a year, about 95 percent of the Aedes mosquitoes in the 12 release zones harbored Wolbachia.
-
The team found that just 2.3 percent of feverish people who lived in the Wolbachia release zones had dengue, compared with 9.4 percent in the control areas. Wolbachia also seemed to work against all four dengue serotypes, and reduced the number of dengue hospitalizations by 86 percent.
-
Even then, these already remarkable numbers are likely to be underestimates. The mosquitoes moved around, carrying Wolbachia into the 12 control zones where no mosquitoes were released. And people also move: They might live in a Wolbachia release zone but be bitten and infected with dengue elsewhere. Both of these factors would have worked against the trial, weakening its results
-
The Wolbachia method does have a few limitations. The bacterium takes months to establish itself, so it can’t be “deployed to contain an outbreak today,” Vazquez-Prokopec told me. As the Yogyakarta trial showed, it works only when Wolbachia reaches a prevalence of at least 80 percent, which requires a lot of work and strong community support
-
The method has other benefits too. It is self-amplifying and self-perpetuating: If enough Wolbachia-infected mosquitoes are released initially, the bacterium should naturally come to dominate the local population, and stay that way. Unlike insecticides, Wolbachia isn’t toxic, it doesn’t kill beneficial insects (or even mosquitoes), and it doesn’t need to be reapplied, which makes it very cost-effective.
-
Wolbachia also seems to work against the other diseases that Aedes aegypti carries, including Zika and yellow fever. It could transform this mosquito from one of the most dangerous species to humans into just another biting nuisance.