We finally may be able to rid the world of mosquitoes – but should we?

The Age

3 days ago

In their labs, the scientists have introduced a gene mutation that causes female mosquito offspring to hatch without functional ovaries, rendering them infertile. Male mosquito offspring can carry the gene but remain physically unaffected.
The concept is that when female mosquitoes inherit the gene from both their mother and father, they will go on to die without producing offspring. Meanwhile, when males and females carrying just one copy of the gene mate with wild mosquitoes, they will spread the gene further until no fertile females are left – and the population crashes.
Simoni said he hopes Target Malaria can move beyond the lab and deploy some of the genetically modified mosquitoes in their natural habitats within the next five years. The non-profit research consortium gets its core funding from the Gates Foundation, backed by Microsoft co-founder Bill Gates, and Open Philanthropy, backed by Facebook co-founder Dustin Moskovitz and his wife, Cari Tuna.
'We believe that this technology can really be transformative,' Simoni said.
At the heart of Target Malaria's work is a powerful genetic tool called a gene drive.
Under the normal rules of inheritance, a parent has a 50-50 chance of passing a particular gene on to an offspring. But by adding special genetic machinery – a gene drive – to segments of DNA, scientists can rig the coin flip and ensure a gene is included in an animal's eggs and sperm, nearly guaranteeing it will be passed along.
Over successive generations, gene drives can cause a trait to spread across an entire species' population – even if that gene doesn't benefit the organism.
In that way, gene drives do something remarkable: They allow humans to override Charles Darwin's rules for natural selection, which normally prod populations of plants and animals to adapt to their environment over time.
'Technology is presenting new options to us,' said Christopher Preston, a University of Montana environmental philosopher.
'We might've been able to make a species go extinct 150 years ago by harpooning it too much or shooting it out of the sky. But today we have different options, and extinction could be completed or could be started in a lab.'
When so many wildlife conservationists are trying to save plants and animals from disappearing, the mosquito is one of the few creatures that people argue is actually worthy of extinction.
Forget about tigers or bears; it's the tiny mosquito that is the deadliest animal on Earth.
The human misery caused by malaria is undeniable. Nearly 600,000 people died of the disease in 2023, according to the World Health Organisation, with the majority of cases in Africa.
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On the continent, the death toll is akin to 'crashing two Boeing 747s into Kilimanjaro' every day, said Paul Ndebele, a bioethicist at George Washington University.
For gene-drive advocates, making the case for releasing genetically modified mosquitoes in nations such as Burkina Faso or Uganda is straightforward.
'This is not a difficult audience, because these are people that are living in an area where children are dying,' said Krystal Birungi, an entomologist for Target Malaria in Uganda, though she added that she sometimes has to fight misinformation, such as the false idea that bites from genetically modified mosquitoes can make people sterile.
But recently, the Hastings Centre for Bioethics, a research institute in New York, and Arizona State University brought together a group of bioethicists to discuss the potential pitfalls of intentionally trying to drive a species to extinction.
In a policy paper published in the journal Science last month, the group concluded that 'deliberate full extinction might occasionally be acceptable, but only extremely rarely'.
A compelling candidate for total eradication, according to the bioethicists, is the New World screwworm fly. This parasitic fly, which lays eggs in wounds and eats the flesh of both humans and livestock, appears to play little role in ecosystems. Infections are difficult to treat and can lead to slow and painful deaths.
Yet it may be too risky, they say, to use gene drives on invasive rodents on remote Pacific islands where they decimate native birds, given the non-zero chance of a gene-edited rat or mouse jumping ship to the mainland and spreading across a continent.
'Even at a microbial level, it became plain in our conversations, we are not in favour of remaking the world to suit human desires,' said Gregory Kaebnick, a senior research scholar at the institute.
It's unclear how important malaria-carrying mosquitoes are to broader ecosystems.
Little research has been done to figure out whether frogs or other animals that eat the insects would be able to find their meals elsewhere. Scientists are hotly debating whether a broader 'insect apocalypse' is underway in many parts of the world, which may imperil other animals and plants that depend on them for food and pollination.
'The eradication of the mosquito through a genetic technology would have the potential to create global eradication in a way that just felt a little risky,' said Preston, who contributed with Ndebele to the discussion published in Science.
Instead, the authors said, geneticists should be able to use gene editing, vaccines and other tools to target not the mosquito itself, but the single-celled Plasmodium parasite that is responsible for malaria.
That invisible microorganism – which a mosquito transfers from its saliva to a person's blood when it bites – is the real culprit.
'You can get rid of malaria without actually getting rid of the mosquito,' Kaebnick said, adding that intentional extinction should be an option for only 'particularly horrific species'.
But Ndebele, who is from Zimbabwe, noted that most of the people opposed to the elimination of the mosquitoes 'are not based in Africa'.
Ndebele has intimate experience with malaria; he once had to rush his sick son to a hospital after the disease manifested as a hallucinatory episode.
Still, he and his colleagues expressed caution about using gene-drive technology.
Even if people were to agree to rid the globe of every mosquito – not just Anopheles gambiae but also ones that transmit other diseases or merely bite and irritate – it would be a 'herculean undertaking', according to Kaebnick.
There are more than 3500 known species of mosquito, each potentially requiring its own specially designed gene drive. And there is no guarantee a gene drive would wipe out a population as intended.
Simoni, the gene-drive researcher, agreed that there are limits to what the technology can do. His team's modelling suggests it would suppress malaria-carrying mosquitoes only locally, without outright eliminating them.
Mosquitoes have been 'around for hundreds of millions of years', he said. 'It's a very difficult species to eliminate.'