PIRACICABA, Brazil — One early morning in February, Cecilia Kosmann hopped in a big gray van loaded with 245,000 mutant male mosquitos and began her daily ride around this sleepy district.
Every 150 feet or so, on streets of tile-roofed, single-story homes, she would grab one of the van’s hundreds of plastic buckets, each filled with 1,000 of the special insects, rip off the lid, and thrust the container into a tube attached to the van’s side window. Then she’d shake the container to usher the bugs out.
A few bugs inevitably backed up into the van, buzzing in ears and catching in hair. (Fortunately, male mosquitoes don’t bite.) By the sixth bucket, two of the bugs flew into her mouth, and she swallowed them.
When someone pointed it out to her, she shrugged. “They get everywhere.”
Riding around in a truck filled with genetically altered mosquitoes is a normal day for Kosmann, an entomologist who has been following this monotonous routine for the past 10 months. “It’s a life dream,” she joked.
Once freed, the mosquitoes fly, mate, pass on a lethal gene to their offspring, and finally die — fast. They were genetically engineered by Kosmann’s company, the British biotech firm Oxitec, to die after about four days, far sooner than the month-ish lifespan of a wild mosquito.
This city of 400,000 people outside of Sao Paulo is the only place in the world currently releasing transgenic mosquitoes into the wild, in the hopes of slashing their numbers. Aedes aegypti mosquitoes carry the Zika virus, now linked to thousands of cases of birth defects in a burgeoning outbreak, as well as malaria, the global scourge that killed perhaps 438,000 people in 2014, and dengue, the bleeding disease that kills about 12,500 people every year.
As Kosmann, a field trial supervisor with Oxitec, put it: “We’re fighting mosquitoes with more mosquitoes.”
In January, Oxitec reported that releases of these transgenic mosquitoes had reduced the wild population by 82%. Brazil’s National Biosafety Committee approved the mutant mosquitoes for release nationwide in 2014, and so Oxitec, based in Oxford, England, is building a bigger breeding facility in a nearby town, poised for a final sales approval from Brazil’s national government.
While the rest of the world debates the economic and ecological impact of these mutant mosquitoes, the people of Piracicaba are surprisingly blasé, and even grateful for them. That’s despite a daily morning onslaught of ardent male mosquitoes looking for mates.
After World War II, South America nearly wiped out the Aedes aegypti mosquito and ended the scourge of yellow fever, thanks to a robust public effort to use more insecticides and drain the puddles, sewers, and tires where mosquitoes breed. But the effort ultimately failed, a victim of its own success as public disinterest led to budget cuts. The mosquitoes came roaring back in the early 1980s, many of them now immune to insecticides.
Fighting mosquitoes with mosquitoes is not a new idea. For decades, public health officials in South America and elsewhere have released swarms of sterile male mosquitoes to curb populations of disease carriers. Those males, typically zapped with the radioactive element cesium to make them sterile, will mate with females, but have no offspring.
Oxitec’s mosquitoes take this a step further: They possess a gene that is deadly if the insect doesn’t ingest an antibiotic called tetracycline, which isn’t found in the wild. The mutant bugs released from the van receive a dose of tetracycline as larvae, allowing them to survive just long enough to pass along their deadly inheritance to their offspring.
Every day, Kosmann aims to release enough mosquitos from the van so that mutant males will outnumber wild ones by 10 to 1. Since one mating fills a female Aedes aegypti with enough sperm to last most of her natural life, as well as a sperm plug (mosquito sex is...complicated) that blocks competing sperm, mating with a mutant male ensures that her offspring will die.
Since 2009, when Oxitec first tested its transgenic Aedes aegypti in Grand Cayman in the Caribbean, a debate has raged over whether using genes to wipe out mosquitoes is a good idea. Some ecologists worry that wiping out a species of mosquitoes might have unforeseen consequences for creatures that feed on them. There are also concerns that genes might jump from one species of mosquito to another, or that the bugs might evolve defenses to lethal genes that would make them harder to kill than ever.
For these reasons, according to a 2011 commentary by Georgetown University’s Graciela Ostera and Lawrence Gostin, transgenic insects should be introduced into the environment only “as a last resort.”
But with dengue rife and the Zika virus spreading to about two dozen countries in the last two months, perhaps that time has come. Oxitec’s success in the Brazilian city has led World Health Organization scientists this month to recommend transgenic mosquitoes for the first time as a tool to combat an outbreak of Zika in Brazil.
“I support the use of transgenic mosquitoes but through a carefully controlled release that monitors the effects on mosquito-borne diseases as well as any potential ecological harms,” Gostin, a global health law expert at Georgetown, told BuzzFeed News by email. He noted the transgenic bugs seem to have cut numbers only of their disease-carrying kin, so far without hurting anything else.
Oxitec’s two-story breeding facility near Piracicaba is about the size of an auto repair shop, and is tucked into a row of warehouses in an industrial park.
Inside, the white-walled rooms look more like a scaled-up university lab than a factory floor. Breeding trays reek with the sauerkraut tang of fish food that nourishes the mosquito larvae. The transgenic bugs are reared by hand from dry eggs to swimming pupae to flittering mosquito on an eight-day schedule.
“What we are doing is using the biology of the mosquito, what makes it so dangerous, against it,” Oxitec’s research supervisor Sofia Ponto told BuzzFeed News.
For the past 10 months, Oxitec has been spreading its mosquitoes in neighborhoods comprising about 5,000 people. Last month, the city agreed that Oxitec could expand its coverage to up to 60,000 residents, aiming to release them in the busy city center. So Oxitec is building a larger mosquito factory, one than can produce more than 2 million transgenic mosquitoes every day.
For Aedes aegypti, that starts with the mosquitoes’ eggs drying out for days or weeks. The researchers collect mosquito eggs, which look like black, powdery grit, on contact paper at the bottom of dozens of breeding cages stuffed with 12,000 females and 4,000 males. Dried aegypti eggs can survive for months, which makes their removal from dried puddles almost impossible since they just look like dirt. But it also allows Oxitec to store eggs until they are needed in drawers in the breeding facility, measured out by weight. One gram of eggs equals about 100,000 mosquitoes.
All of the mutant mosquitoes bear the lethal gene, which in the absence of tetracycline destroys a mosquito’s metabolism along varied biochemical pathways. That makes it “practically impossible” that wild mosquitoes will evolve defenses to the gene, according to Ponto, a geneticist.
Just add water and a little tetracycline and those dried eggs hatch, growing into fat little pupae in five days. Trays of larvae are borne about the facility for testing by technicians in white lab coats, who follow a choreography reminiscent of a busy restaurant kitchen as they move the bugs along in their life cycle.
Another quirk of Aedes aegypti biology allows the staff to cull the male pupae from the females: “The males are skinnier,” Ponto said. Simply submerging the pupae underneath a wire mesh of the right size allows the males to swim upward to breathe air and be collected while their fatter sisters drown.
Collected into plastic buckets that look exactly like takeout containers, the pupae grow into the mosquitoes released by van a few days later.
“Aside from the lethality gene, they are just male mosquitoes like any other,” Ponto said. (Well, almost: The bugs also possess a fluorescence gene that allows them to be monitored under filtered light.) “We really need to develop a sexy mosquito next, to make sure they are mating like we want.”
In Piracicaba, at the corner of Cabralia Paulista and Afonso Jose Fioravante streets, Maria Madalena de Almeida Raiane told BuzzFeed News about April 30, 2015, the day that the mutant mosquitoes were released for the first time in front of her house. The street was full of reporters and her house was on the evening news.
“We thought, OK, we're gonna be rat labs for these mosquitoes. But I got used to them,” she said in Portuguese. “Yeah, there are lots of mosquitoes. We must stand them. It would be good if they released the mosquitoes all over the city to end dengue in the other neighborhoods.”
Only her son, who works at night and then sleeps when the van arrives, complains about the morning flurry of male mosquitoes because they are annoying, she added. “When you're having food, they annoy too. Yesterday, my sister came over and we couldn't eat because of the mosquitoes.”
Mutant mosquitoes don’t bother Celso Luis Caprani, a retired orange-juice seller who lives a few blocks away from her. “No, no. The project has been taking place for a year. Nothing ever happened. Keep releasing them!” he told BuzzFeed News in Portuguese.
Caprani had dengue three years ago and doesn’t want it again. “It was hard,” he said. “For a month, I had rashes, it itched a lot.”
In truth, the mutant mosquitoes are the easy part of Oxitec’s project. People are the hard part, with the local PSF 1 health clinic and Oxitec scientists doing a lot of explaining before it started.
“Before the project started, we informed the community,” health clinic nurse Debora Duraes, who is eight months pregnant and concerned about the Zika outbreak, told BuzzFeed News. “Oxitec did not show up here releasing mosquitoes without telling them. We went from door to door to present the project.”
Piracicaba had 3,962 confirmed cases of dengue in 2015, which explains the interest of the city’s mayor, Gabriel Ferrato, in trying transgenic mosquitoes. The pilot project cost roughly $50,000, which the city split with Oxitec. A two-month publicity campaign sold the community on the effort, with surveys suggesting that more than 9 out of 10 locals are in favor of the mosquitoes.
A proposal by mosquito control officials to try the Oxitec mosquitoes in Key West, Florida, in contrast, has faced a lot of local opposition, with 155,000 people signing a petition against trying them on one small island of 400 people.
"Much of the political and public opposition to transgenic mosquitoes comes from relatively privileged groups in high-income countries,” said Gostin, of Georgetown. “They are well-meaning, but they do not suffer the devastating impact of malaria, dengue, yellow fever, and other serious diseases.”
That’s not to say that the people of Piracicaba were always on board.
“In the beginning, yes. There were a lot of scared people,” clinic local health agent Maria do Carmo Tunussi, who has been working in the area for 16 years and is known to everyone as “Carmina,” told BuzzFeed News. “But the community is happy now because of the results.”
A year ago the local health clinic saw five or six cases of dengue a day. This January it saw just three cases, which is actually an increase from past months, and those look like infections caught away from the city. Far south of the center of the Zika virus outbreak in Northeastern Brazil, Piracicaba reported only its second confirmed Zika virus infection last week, in a woman who was 19 weeks pregnant. Ultrasound tests showed no signs of brain damage in her fetus, but she is undergoing more tests.
With dengue still rampant and Zika threatening, Carmina said she is happy to be annoyed by the mutant mosquitoes, with about 800,000 released every week from Oxitec’s van. (At this point, with the wild population down, that’s more of a maintenance dose of mutants, down from the millions a week released when the project started in April.)
As the van crawls along, the steady release of the bugs is a final bit of biological warfare in the fight against wild mosquitoes. Aedes aegypti are lazy and seldom travel very far, preferring to hover in the shadows of the homes of their favorite prey, people — so the frequent releases of 1,000 males per bucket saturates the district with quick-dying mutants.
“I get up early, at 5 a.m., so we can release them early in the morning when people won’t be as annoyed by all the mosquitoes,” Kosmann said. For herself, she said, with a laugh, “I don’t even notice them anymore, even when I eat one by accident.”
Bruno Romani contributed reporting and translation to this story.