Inside a small building in eastern Rio de Janeiro, Brazil, Cátia Cabral holds up a jar filled with what looks like fine black pepper. But this ain't pepper. Each granule is actually a tiny mosquito egg.
Cabral estimates this container holds some half a million eggs.
Next door, untold numbers of tiny larvae wriggle in bins filled with water. "It's like it's the mosquito nursery room," she says through an interpreter.
In another large room, mesh cages teem with mosquitoes that feast on small bags of blood.
Cabral is a biologist at the nonprofit World Mosquito Program who supervises this place, which amounts to a finely tuned, high tech bug-making factory where mosquitoes are bred by the millions.
The thought of all these mosquitoes might make one's skin crawl. But Cabral thinks of them as her babies, and she says these insects deserve more praise than loathing. That's because they've been engineered to shut down the transmission of the very diseases they usually carry and spread.
And it's why the Brazilian government has made a massive investment to create and deploy this tiny winged armada across the country — to join their other national efforts to combat mosquito-borne diseases.
Cabral has every confidence in these mosquitoes. "They can help us," she says.
A devastating disease
Mosquitoes are small but lethal in many parts of the world due to the diseases they carry.
In Brazil, dengue has wrought havoc on millions of people. Severe forms of the disease, if not treated, damage the blood vessels and make them leak like sieves, which can lead to high fever, shock, internal bleeding, organ failure and even death.
"The first thing to do is to start giving fluids," says Dr. Otavio Haguiuda Jr., a family physician who's worked in different parts of Brazil including, currently, the southern city of Joinville. "It's the most important measure."
Haguiuda has seen his fair share of this debilitating disease and has suffered from it himself three times.
"It's terrible," he says. "It hurts like our bones are being broken. I worked in an endemic zone and it was very bad. And yes, I had people who died of dengue."
Brazil accounts for the bulk of dengue across the Americas. Already this year, there've been over 3.1 million cases in the country.
"It makes me sad because we've had many losses," says 53-year-old Lucia Jordan, a health worker in Joinville. "Many people died," including a neighbor she was close with who was admitted to the hospital but never came home. He left behind his wife and two kids.
The World Health Organization reports that dengue numbers have not only multiplied dramatically in the last couple decades but the disease is now showing up in new places, including within Europe and North America. Warmer, wetter conditions due to a changing climate have helped facilitate the spread of Aedes aegypti, the mosquito that carries the virus.
When an outbreak surges in Brazil, Haguiuda has observed how it can devastate an already strapped health system. In a word, the result is "chaos," he says. "We are already working at 100 to 110%. When dengue comes, we have to slow down other treatments."
For weeks, patients with conditions like diabetes or hypertension have to wait for treatment until the dengue cases subside.
Haguiuda says those who are poorer are often unable to keep from getting bit by the mosquitoes that carry the virus in the first place. "They don't have means to protect themselves from the mosquito," he says. "Many can't buy pest repellents. They can't put screens on the windows."
There's soon to be a Brazilian-made dengue vaccine to complement two others already on the market. However, since COVID, anti-vax sentiment and doubts surrounding vaccines have grown, according to José Henrique Copi, the president of the health council in Joinville, which is a politically conservative community.
"The dengue vaccine, it was tested, it was approved, it showed high efficiency," he says through an interpreter. "But now we are dealing with this doubt."
So Brazilian government and public health officials pondered what they could do to combat the disease more forcefully.
That's where those special mosquitoes buzz into the picture.
A bacteria inside a bug
The insects that hatch inside the bug factory in Rio have been engineered to contain a set of microbial stowaways — a kind of bacteria called Wolbachia. It's naturally present in roughly half of all insect species, including some mosquitoes, says Diogo Chalegre, a biologist who worked at the World Mosquito Program until recently.
Remarkably, this bacteria and the virus that causes dengue are unable to coexist inside the mosquito that transmits this disease.
"It's like there is a competition between Wolbachia and the virus," says Chalegre. "So once Wolbachia is inside these mosquitoes, the virus cannot replicate."
And if dengue can't replicate, then mosquitoes can no longer transmit the virus when they bite someone. So Chalegre's colleagues wondered whether they could use Wolbachia to stop dengue from spreading.
"We're Buddhist in our approach, letting [the mosquitoes] stay alive," says Scott O'Neill, the scientist who founded the World Mosquito Program and dreamed up this idea years ago. "We're just making them harmless to people."
The only problem was that the mosquitoes they needed to target don't naturally carry Wolbachia. The team had to use a very fine glass needle to introduce the bacteria into mosquito eggs, a daunting task that took longer to succeed than finding a regular needle in a haystack — five years. But at last they managed it, creating what they call "Wolbitos."
"Wolbachia plus mosquito equals Wolbito," says Chalegre with a chuckle.
These modified mosquitoes pass the bacteria on to both their mates and their eggs. "So you don't have to inject again Wolbachia into these mosquitoes," says Chalegre. And once the technique was shown to work in laboratory studies and field trials in Australia and Indonesia, the World Mosquito Program was ready to attempt it at a grander scale.
This is why the Brazilian Ministry of Health — in partnership with Fiocruz, its health research and development institution — and the World Mosquito Program are breeding and releasing swarms of Wolbitos in the country. Alongside other countermeasures, they want to make it the dominant mosquito in Brazil in the hope that the number of dengue cases will plummet, along with other mosquito-borne viruses like chikungunya and Zika.
Alexandre Padilha, the Minister of Health, took to social media earlier this month to explain the country's ambitious target — to protect 140 million Brazilians across 40 municipalities against dengue over the next decade.
It's a goal whose rationale appears to be well-founded.
A world of difference a mere bridge away
Across the bay from Rio de Janeiro, in the neighboring, poorer city of Niterói, Fiocruz and the World Mosquito Program, in tandem with local health workers, began releasing Wolbitos in 2015.
"We were all so nervous at the beginning," says Fábio Vilas-Boas, the head of Niterói's Center for Zoonosis Control. "Historically, we've always tried to kill the mosquitoes and then suddenly we were releasing them. So it was kind of counterintuitive."
Public health officials realized they needed to inform community members of the approach.
Raíssa Vieira, a community health worker in Niterói, had previously spoken with residents about the best ways to reduce mosquito habitat in and around their homes. She soon turned to going door to door to explain the Wolbito initiative.
"Our work is to talk to the community one by one, each house by each house," she says through an interpreter. "We talk to everyone, explaining what would be done. It's like the work of an ant — little by little, piece by piece."
Some households required more explaining than others, but overall, Vieira says there was widespread support. And she admits that a clear benefit to the approach is that its effectiveness doesn't depend on the public.
"You don't need to rely on people's actions to be effective," she says. "You just release the mosquitoes and it naturally works."
Officials say that nearly all the mosquitoes in Niterói now carry Wolbachia. As a result, the World Mosquito Program, Fiocruz, and local health authorities documented a roughly 90% drop in what had been several thousand cases of dengue annually when comparing the 10 years prior to Wolbito introduction to the five years afterward.
In contrast, just across the bridge, in neighboring Rio de Janeiro where the modified mosquitoes have not yet been introduced, dengue levels have remained reasonably high during the same period.
The levels of two other mosquito-borne viruses in Niterói — chikungunya and Zika — also fell by over 96% and 99%, respectively, when comparing the roughly five years before and after Wolbito introduction. Case counts dropped from the thousands to a mere handful.
For Anamaria Schneider, the city's health secretary, these reductions help her focus on other priorities. "Now I can put our efforts into other fronts of work — not forgetting dengue but strengthening other tasks, other activities," she says.
Schneider says they refer to the Wolbito in Portuguese as "mosquito du bem" — "the good mosquito."
Small concerns with hopes for big payoffs
There are those who worry that the virus will evolve a workaround — that Wolbachia won't be able to keep these diseases at bay forever. But Johanna Fraser, a virologist at a medical research nonprofit in Melbourne called the Burnet Institute, says so far, she and her team have seen little indication of this.
"You could have the virus adapt," she says. "You could have the bacteria adapt. You could have the mosquito adapt. But all of these things so far do not seem to be happening. Evidence to date suggests it is going to be a very effective solution."
O'Neill concurs. "We've had a lot of opportunity to look for adverse events or any safety signals," he says. "And nothing has appeared that suggests either resistance to the technology or anything untoward from a safety or environmental perspective."
Still, Fraser acknowledges the Wolbachia approach has its limitations within Brazil, a vast and complex place. "To do it to the stage of eliminating dengue will be really difficult," she says, "simply because it's such a big country and regions might be unsafe." Gang activity in a particular neighborhood, for instance, would make it difficult for workers to release Wolbitos reliably and safely.
There, Mayor Adriano Silva says fighting dengue has become his main focus. "Human life is always a priority," he says by way of explanation.
Late last year and earlier this year, for several months on most weekdays, a team of more than a dozen health workers fanned out across the city to release Wolbitos. Fabiane Rudnick is helping to run the effort. She's a project assistant with the World Mosquito Program and is from Joinville.
She says mosquitoes are abundant in the city because of the high temperatures and all the rain, which has made dengue a big problem. For her, the Wolbitos mean two things — "health and hope," she says. "With my work, I can do something good for for the community."
Tamila Kleine, a Wolbito program manager in Joinville, is proud that the team is improving the health of the people here by rearing and releasing these modified mosquitoes. "It's quite gratifying," she says. "It's amazing to think that these little things that you're working with may have such a big impact for your country."
Soon, it's time for the teams to head out. A series of white Chevy sedans, each loaded with several hundred tubes containing tens of thousands of mosquitoes, drive to different parts of the city.
One of the vehicles follows a route through a residential area in the east called Espinheiros.
Technician Antônio Farias sits in the back. One by one, he holds a tube outside the window, letting a couple hundred of the factory model mosquitoes lift off.
On July 19, a massive new Wolbito factory opened about 80 miles from here in Curitiba. Its goal is to produce some 5 billion mosquitoes in the first year.
Farias continues his work, releasing little puffs of mosquitoes into the morning sunshine. The car inches along, slowly filling the air with the hope of a different future, carried on tiny — albeit annoying — wings.
Lina da Anunciação served as the interpreter for interviews conducted with Portuguese speakers.
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