Stat goes to the front-line laboratories in French Polynesia, where scientists are beating back mosquitos in revolutionary ways:
Hervé Bossin and his team have released more than 1 million sterile male mosquitoes since September, triggering a hundredfold drop in the mosquito population on one islet of Tetiaroa, formerly a retreat for Polynesian royalty.
Mosquitoes cause more human illness than any other creature on earth, killing 800,000 children a year, on average. The biting females carry malaria, dengue, yellow fever, and — most recently — Zika, which is suspected of triggering birth defects and neurological damage in some patients.
“All of this happens because of mosquitoes,” said Bossin.
Mosquito control usually involves spraying chemicals and asking people to clean up sources of standing water in their yards.
But these traditional methods won’t halt the global spread of disease, said Bossin, who heads the mosquito lab at the Institut Louis Malardé in Tahiti, the largest of the Polynesian islands.
Spraying insecticide can be toxic to other creatures. People too easily slip back into habits that allow the insects to flourish; they leave standing water in trash piles, flower pots, pet bowls, and backyard pools. Mosquitoes lay eggs unseen in ship’s hulls and inside packing crates and airplanes, allowing them to spread to new habitats. And people carry diseases from one time zone to another — once bitten by a mosquito, their sickness can be transmitted to others.
“Response is a losing battle,” Bossin said, urging more aggressive steps to thwart disease outbreaks before they can start. “All we can do is prevention.”
Bossin, a medical entomologist, estimates that there were tens of thousands of biting mosquitoes on Tetiaroa’s main islet, Onetahi, when he began releasing sterile males there in September. At the peak of last year’s rainy season, each of the 20 traps he set collected an average of 16 biting females a day. (Only the females suck blood, when they need extra energy to lay eggs.) Now, he’s hard-pressed to find more than a dozen across the whole islet.
He’s taking a two-pronged approach: In one, he wants to prevent mosquitoes from spreading disease in populated areas, and in the other, intended for resorts, he aims to get rid of mosquitoes entirely.
A bacterium called Wolbachia is his weapon of choice for both. Wolbachia live inside many insect species, including numerous mosquitoes. Infect the Aedes aegypti mosquito with Wolbachia, and the mosquito responsible for spreading dengue, chikungunya, West Nile and other viruses can no longer pass these diseases on to people, a handful of scientific teams around the world have shown.
Simmons and his colleagues have been testing Wolbachia-infested mosquitoes in field trials for the last five years in Australia, and they are now scaling up their work into larger cities in Vietnam and Java.
When a Wolbachia-infested male inseminates an uninfected female, she will never be able to lay viable eggs. But when infested females mate — regardless of the status of the male — their offspring inherit the Wolbachia. This means that over just a few generations, all the mosquitoes in a population will be infested — and apparently unable to spread disease.
Simmons anticipates it will cost under $1 per person to release enough infested females to block mosquitoes from passing on dengue.