ETIAROA, French Polynesia — On this remote South Pacific atoll owned by Marlon Brando’s family, a French biologist is undertaking an ambitious experiment that could help change how we fight mosquitoes — and the diseases they spread.
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.
Zika struck this part of the South Pacific in 2013-2014 before jumping to the Americas last year, where it has swept through two-dozen countries. Bossin didn’t catch Zika, but several colleagues did, as did an estimated 60 percent of the population of French Polynesia, a collection of five archipelagos just east of the international date line and 2,600 miles south of Hawaii.
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.”
An ideal natural laboratory
Bossin stood outside a research station on Tetiaroa’s main islet one muggy day last month. “A year ago, if you were here during the day, you would have been surrounded by mosquitoes and bitten,” he said. On this day, none was in sight.
The tiny island is one of 12 surrounding a turquoise lagoon. The atoll grabbed global headlines when Marlon Brando bought it in 1967. He fell in love with the place while filming “Mutiny on the Bounty” in nearby Tahiti. He also fell in love with his Polynesian costar, Tarita Teri’ipaia, who became his third wife.
Several of their grandchildren still live in Tetiaroa; one, Manea, who inherited his grandfather’s jawline, helps Bossin with his research. They share the atoll with an ultra-exclusive, environmentally friendly resort called The Brando, where couples can stay for $2,600 a night; and a research station run by the Tetiaroa Society, a nonprofit dedicated to scientific research that promotes sustainable interdependence between people and nature.
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.
Islands, Bossin said, are “ideal settings” for doing this kind of work. They are natural laboratories, a way to start simply, get a clear picture of causes and effects, and then move on to more complex systems, he said.
His research is time-consuming and expensive, running about $300,000, half paid by the local and the French governments, and half coming from in-kind contributions from the Tetiaroa Society and the resort. For now, his work is designed to keep mosquitoes away from the tourists, who come to Tetiaroa to fish, snorkel, take in the incredible views, and maybe learn a little science. Bossin is happy to explain his work to anyone who is interested, figuring it can’t hurt for wealthy people to learn about what he does.
Some might object to the effort he spends protecting mostly white, rich people. But Bossin, who earned an MBA in addition to his PhD, knows that there will be no jobs for locals if mosquitoes scare off Polynesian pleasure-seekers.
If the approach works here, he plans to export it to other resorts across the South Pacific, and maybe the world.
“Other resorts and private islands have already expressed interest and are waiting to see the results of our Tetiaroa operation,” he said in an email.
On a sweaty, overcast morning last month, Bossin set off in a motorboat steered by Manea Brando to the far side of the lagoon, to two islets he uses as experimental controls — where he hasn’t released sterile mosquitoes.
As they eased between sandbars and chunks of coral, young black-tipped and yellow sharks zigzagged by, rays sped just below the water’s surface, and a sea turtle crossed their path.
Wading ashore onto the first islet, Bossin and graduate student Margaux Jourdainne headed into the dense coconut groves planted a half-century earlier to boost coconut oil exports.
Bossin hurriedly slipped the protective green trash bag off a mosquito trap. He linked the wires of a battery and checked that the tiny fan whirred, sending out an aroma to lure in the insects. He stretched netting over the top to prevent escape and moved on.
His motions were fluid and fast. To show why, he stood still for 30 seconds, bare arm outstretched. A mosquito landed and prepared to dine.
Bossin could easily have crushed the bug. But he is not that kind of man. He shooed it away instead.
Humbled by mosquitoes
Bossin, who spent childhood afternoons absorbed by the insects in his suburban Paris backyard, finds mosquitoes fascinating.
There are 3,500 named species of mosquitoes across the world, but only about 200 are a nuisance to humans. In French Polynesia, of the 15 local species, only three – Aedes aegypti, Aedes polynesiensis, and Culex quinquefasciatus – threaten human health.
He’s impressed that mosquitoes can survive in so many parts of the world.
“Even though I’m working to reduce the damage they do to us, I’m still very humble in the face of such species — such a level of adaptation to the environment,” he said.
Bossin was originally headed for life as a “lab rat” studying genetics, he said, but his early work left him feeling he wasn’t making enough of a difference in the world.
After earning a PhD in France, he did postdoctoral research for the US Department of Agriculture in Gainesville, Fla., for three years, where he learned to fluently speak the kind of American English that quickly endears him to tourists and foreign colleagues.
Bossin greets everyone from hotel staff to scientists by first name and with the French-style quick kiss on each cheek.
He worked for the United Nations in Vienna studying mosquito-borne diseases, and in 2005 attended a public health conference in French Polynesia, where he met the head of the Institut Louis Malardé’s mosquito lab. He helped the institute run a field study, and, he said, “a couple of years later, I was the one running the show.”
Harnessing bacteria that infect mosquitoes
In a sort of ironic twist, Bossin hopes to stop mosquitoes by infecting them.
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.
Although this approach still has to be proven effective against Zika, its broad effectiveness suggests it will be. “We have every expectation that they’ll also be resistant to Zika,” said Cameron Simmons, a Wolbachia expert and professor at the University of Melbourne in Australia.
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. That is far less than spraying or genetically engineering mosquitoes — an approach being tried by other scientists — although he says that a variety of complementary approaches will be needed to contain disease.
None of hundreds of studies has seen any negative consequences from infecting mosquitoes with Wolbachia — because the bacteria are already present in the environment and are not transmitted to predators, said Steven Sinkins, a Wolbachia expert at Lancaster University in the United Kingdom. The work does not require genetic engineering, he said, quieting concerns about tinkering too much with nature.
Wolbachia also acts in several ways to keep mosquitoes from passing on disease, Sinkins said, so it is unlikely that the insects can evolve to become less vulnerable to it.
Sinkins is getting ready to release Wolbachia-infected mosquitoes in Malaysia as part of a research project, and is optimistic that studies like his will show that such mosquitoes can be a safe, effective way of preventing mosquito-borne diseases.
“I hope very much that this will be Wolbachia’s decade,” Sinkins said.
An unwelcome visitor
The experiment on Tetiaroa is one of the first to test whether releasing sterile, Wolbachia-infested male mosquitoes can completely and safely erase mosquitoes from an ecosystem. Bossin is starting with one island, and then will expand to the whole atoll. Eventually, he wants to protect the entire Polynesian archipelago.
“Our goal is not to remove [polynesiensis mosquitoes] from the earth,” Bossin said. “It’s to make sure that on populated islands, we are no longer exposed.”
Every Monday and Tuesday morning in his Tahati lab, a technician takes Wolbachia-infected mosquito pupae and gently drops them between two tilted glass plates. Like in a coin sorter, the smaller male pupae slip further down between the plates, while the bigger females get stuck closer to the top, enabling relatively easy gender separation.
On Tuesdays at midday, the pupae are packaged and flown on a small plane to Tetiaroa’s research station where they will spend another day maturing, 650 to a white plastic tub.
Thursday mornings, Manea Brando stacks dozens of tubs in a golf cart and drives around the islet, opening them one at a time in different spots. Tens of thousands of sterile males fly off in search of mates, hopefully ending the family tree of Onetahi’s polynesiensis.
So far, Bossin said he’s seen no downside to the elimination. There are no bats or frogs in French Polynesia to feast on mosquitoes, and no insect-eating bugs on the atoll. Spiders have plenty of other options.
Aedes polynesiensis was introduced to Polynesia 1,000 years ago, as people from Fiji began to populate the Polynesian archipelagos. “It was an introduced, invasive species that does not sustain other species,” Bossin said.
Aedes aegypti arrived in the South Pacific about 200 years ago, aboard boats from Africa. It spread widely throughout French Polynesia only after World War II, with the urbanization of atolls across the territory.
“It could never have come here without the presence of humans,” Bossin said. Although climate change likely plays a role in the expansion of mosquito habitats worldwide, he said, “the population genetics of mosquitoes exactly maps the movement of people.”
Bossin plans to monitor the mosquito population to ensure the population doesn’t rebound. He may need to release more sterile males, he said, but it’s too soon to know.
Walking through the densest area of Onetahi, Bossin paused to marvel at his own success. Just a few years ago, the workers who built the guest villas on the islet were constantly complaining about the mosquitoes. “It feels incredibly comfortable here now,” he said. “Elimination is within reach.”
Returning from Tetiaroa to Tahiti takes 2 1/2 hours by boat or 20 minutes by a six-seat airplane. On one recent trip, as the five passengers scrambled aboard, a stowaway came along, too. A fly buzzed around the cabin during the flight and disappeared on landing.
It wasn’t a mosquito, but its presence showed just how easily people can transport insects from one place to another, and what Bossin and other scientists are up against, as they try to stop this invasive creature and the disease and misery it spreads.