2023-09-13 05:39:04
TEGUCIGALPA (AP) — Buzzing inside a jar are the new allies in the fight against dengue: more than 200 mosquitoes desperate to get out.
For decades, preventing this disease has meant getting rid of these insects. Now in that jar is a potentially more effective way to control evil that defies everything we’ve learned.
That is why there is applause and joy in a neighborhood with a high incidence of dengue fever north of Tegucigalpa when Héctor Enríquez, a 52-year-old bricklayer, lifts the boat above his head and removes the cloth that covers it, freeing the mosquitoes.
The mosquitoes that fly next to him seem the same as the ones that everyone used to kill, but they are not. These were bred by scientists and carry a bacteria called Wolbachia that blocks the transmission of dengue. When they reproduce, they transmit the bacteria to their offspring, reducing future outbreaks.
The non-profit organization World Mosquito Program (WMP) is a pioneer in this technique and has been implementing it for more than a decade in a dozen countries. With more than half of the world’s population at risk of contracting dengue, the World Health Organization (WHO) closely follows each of these processes, the most recent being the Honduran one, and finalizes a recommendation to support its use globally. .
In Honduras, which records about 10,000 cases of the disease annually, the WMP has teamed up with Doctors Without Borders (MSF) to release some nine million mosquitoes in six months, in some cases with the help of volunteers like Enríquez.
The idea may seem difficult to sell to the population but Australian Scott O’Neill, founder of WMP, assures that communities are willing to endure a few bites in order to reduce the disease.
“There is a desperate need for new approaches,” he said.
DENGUE DEFIES TYPICAL PREVENTION
In recent decades, science has made progress in reducing infectious diseases, including those caused by mosquito-transmitted viruses such as malaria. But dengue has not stopped increasing.
The WHO estimates that up to 400 million people in about 130 countries are infected each year and although mortality rates are low – about 40,000 deaths annually – their socioeconomic impact is enormous because outbreaks can put health systems in check and make many people miss work or school.
“When you get dengue, it’s often like having the worst flu you can imagine,” said Conor McMeniman, a mosquito researcher at Johns Hopkins University.
There is a reason why it is popularly known as “bone-breaking fever,” the scientist added.
Traditional control methods that have worked on other mosquito-borne diseases have not been as effective against dengue.
Aedes aegypti, the type of mosquitoes that transmit this virus, have become resistant to insecticides that, at best, have had limited effects.
Furthermore, these mosquitoes bite during the day, so sleeping under mosquito nets does not help, and there are still no effective vaccines to control a virus that comes in four different variants.
As if that were not enough, as Aedes aegypti proliferate in hot and humid environments and in densely populated cities, climate change and increasing urbanization suggest that the situation will worsen.
“We need better tools,” said Raman Velayudhan, a researcher at WHO’s Neglected Tropical Diseases Programme. “Wolbachia is definitely a long-term and sustainable solution.”
The WHO, which has already supported research with this bacteria after recurrent epidemics caused by the same type of mosquito – which also transmits Zika, chikungunya and yellow fever – plans to soon publish a document to endorse its use and an operational manual so that countries have it as a reference, which could encourage more governments to use this technique and more donors to be interested in financing it.
BACTERIA THAT BLOCKS THE DISEASE
The Wolbachia strategy has taken decades to develop.
This bacteria exists naturally in around 60% of insects but not in Aedes aegypti, so the challenge was how to transfer it to this mosquito.
About 40 years ago O’Neill, then a young entomologist, became obsessed with doing so. “We worked on it for years,” acknowledged the 61-year-old scientist.
As he recalled, there were years of “impossible projects” and “many tears” but they finally discovered how to transfer the bacteria from fruit flies to Aedes aegypti mosquito embryos using microscopic glass needles.
At that time, scientists were betting on using Wolbachia in a different way: to reduce mosquito populations. Males that carry the bacteria only produce offspring with females that also have it, so the idea was to release infected males to mate with females without Wolbachia so that the eggs would not prosper.
But O’Neill’s team made a surprising discovery. Wolbachia not only affected the procreation process of Aedes aegypti, but the mosquitoes that carried it did not transmit dengue or other diseases.
And since infected females do transmit Wolbachia to their offspring, they opted to use infected mosquitoes to “replace” local populations to block the virus.
According to Oliver Brady, an epidemiologist at the London School of Hygiene and Tropical Medicine, this population replacement strategy—which is what the WMP uses—represented a major change in mosquito control approaches because until then everything had focused “kill mosquitoes or, at the very least, prevent them from biting humans.”
Since O’Neill’s lab first tested the replacement strategy in Australia in 2011, the Global Mosquito Program has conducted studies in 14 countries—including Brazil, Colombia, Mexico, Fiji and Vietnam—potentially protecting an estimated 11 million. of people.
The results are promising. In 2019, a large-scale trial in Indonesia showed a 76% decrease in dengue cases after the release of Wolbachia mosquitoes.
The technique continues to expand. At the beginning of 2024 it will arrive in El Salvador and Brazil wants to apply it nationally.
However, it has challenges ahead. The fundamental ones, according to the WHO, are the high cost and complicated logistics of producing and releasing infected mosquitoes on a large scale. O’Neill agrees. The Tegucigalpa project, which will be developed over three years, will cost $900,000, approximately $10 per person.
Scientists still don’t know how Wolbachia works to block dengue, and unanswered questions include whether the bacteria works equally well against all types of dengue or whether some variants could become resistant to it over time, said Bobby Reiner, Ph.D. academic at the University of Washington.
“The truth is that this is not a single, definitive solution that is guaranteed forever,” Reiner concluded.
BREEDING OF SPECIAL MOSQUITOES
Many of the world’s Wolbachia-infected mosquitoes are born in a not very large warehouse in the Colombian city of Medellín. The WMP breeds 30 million mosquitoes a week here.
The biofactory imports dried eggs from each country where a new project will begin to ensure that the mosquitoes that are released later are descendants of the natives and, therefore, have similar characteristics to the local population, including the same resistance to insecticides, explained Edgard Boquín, MSF project leader in Honduras.
Once in Colombia, the eggs are laid in water with food powders and when the mosquitoes are born, they are crossed with the “mother colony” that has Wolbachia —and where there are more females than males— so that their descendants are born infected.
A constant hum invades the room with the square mosquito cages where the insects mate. The keepers make sure that they do not lack the best food: sugar water for the males; human blood at 37 degrees for females, packed in small plates covered by a skin-like membrane to trick them into stinging.
“We have the perfect conditions of humidity, temperature, availability of blood and everything that has to do with breeding,” said Marlene Salazar, coordinator of the biofactory.
Once the workers confirm that the new mosquitoes carry Wolbachia, the eggs laid by their females are dried, mixed with a powder made from liver and a sugar solution and filled into capsules similar to those of any medication, which are then filled. They will send to the liberation countries.
These atypical shipments are often not free of problems. The first one to arrive in Honduras was detained for hours at the airport customs because the authorities considered that the capsules from Colombia had “suspicious” powder, Boquín said with a laugh as an example of the thousand and one logistical challenges they face every day.
GAIN TRUST, GET HELP
Since the end of August, a scene has been repeated many days at dawn: a dozen young people from Doctors Without Borders ride motorcycles through Manchén, the area in the north of Tegucigalpa chosen for the project, and do their peculiar distribution of mosquitoes with Wolbachia.
They reach a point, uncover a jar, hit it, and if it doesn’t come out, the mosquitoes blow a little because the carbon dioxide from their breathing alerts them that a human they can feed on is nearby and prompts them to look for it.
Then they move on to the next point, about 50 meters away, often after having involuntarily donated some of their blood with one or more stings or answering the questions of a neighbor who still doesn’t know what is happening.
Meanwhile, another group visits several homes in a part of the neighborhood built irregularly on one of the many slopes of the city, an area where water is lacking, diseases are abundant, and access by public servants is scarce because control is held by one of the most dangerous gangs in Central America.
Humanitarian workers can move through those streets, sometimes dirt, thanks to previous information work for the community—gang members included—that began six months ago. In addition, they have the support of volunteers who notify residents of each movement and their reputation for neutrality and transparency in medical action.
These teams carry empty jars, a bag filled with capsules made in Colombia, and water.
Lourdes Betancourt, a volunteer health promoter, accompanies them to half a dozen houses until they reach hers, where the procedure is repeated.
They put a capsule containing the eggs in a jar, put water, cover it and hang it from a tree after putting Vaseline in the side holes so that other insects do not enter. In about 10 days the new mosquitoes with Wolbachia will fly out to mate, spreading the bacteria to others without needing to do anything else.
Some of the most common questions that residents ask—here and in all countries where the same technique has been implemented—is whether Wolbachia harms people or the environment. MSF workers clarify that no, nothing like that happens. They also emphasize that there is no genetic modification of mosquitoes and, therefore, they cannot be called transgenic.
María Fernanda Marín, a 19-year-old student in charge of the humanitarian organization’s insectary – a garage full of jars where mosquitoes are raised until they are released – stated that there is a lot of misinformation on the networks and that, to gain the trust of her neighbors, she shows a photo of his arm covered in bites.
According to him, many of the MSF workers have placed their forearm on the gauze that covers the jars to “donate blood” to the cause and thus demonstrate that, although they bite, these mosquitoes are not dangerous.
Betancourt, who has had dengue on several occasions, acknowledged that at first she had her doubts but after having received all the information, she is now the one who convinces her neighbors to collaborate in the release of “cured” mosquitoes, as she calls them. .
“I tell people not to be afraid, that that is not a bad thing, to have confidence,” she explained. Marín assures them that the mosquitoes “are not going to give them dengue” but she is very sincere: “they are going to give them chop, yes.”
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Burakoff reported from New York. AP journalist Marko Álvarez contributed to this report from Medellín.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. AP is solely responsible for all content.
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