Could wiping out all mosquitoes save lives without harming nature?

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The deadliest animals are not lions, spiders or snakes, but the tiny mosquitoes that suck our blood, make us itchy and infect us with disease.

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Mosquitoes kill around 760,000 people every year, according to research site Our World in Data, with humans ourselves coming a distant second.

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This is because mosquitoes account for 17 per cent of all infectious diseases, including malaria, dengue, yellow fever, chikungunya and Zika.

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And as the world warms due to human-driven climate change, mosquitoes are roaming to new areas during longer summers, raising fears they could propel future health crises.

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So how can humanity fight back against our greatest foe? Is there a safe way we could eradicate these killer mosquitoes — and how bad would that be for the environment?

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– #Notallmosquitoes –

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First, we would not need to vanquish all mosquitoes. Out of roughly 3,500 mosquito species, only around 100 bite humans.

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And just five species are responsible for roughly 95 per cent of human infections, Hilary Ranson, a vector biologist at the Liverpool School of Tropical Medicine, told AFP.

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On balance, Ranson felt that losing five mosquito species “could be tolerated given the huge devastation” they inflict on the world, from mass death to crippling economic fallout.

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Dan Peach, a mosquito entomologist at the University of Georgia, broadly agreed, but emphasised that more information was needed to compare eradication with the alternatives.

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– What about the environment? –

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The five disease-spreading mosquitoes “have evolved to be very closely associated to humans,” including feeding on and breeding near us, Ranson explained.

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This means eradicating them would not have a major impact on the broader ecosystem — and other, genetically similar but less deadly mosquitoes would likely quickly “fill that ecological niche”, she added.

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Peach was not convinced we know enough “about the ecology of most mosquito species to be confident one way or the other, but I also think that it is OK to acknowledge this and still proceed.”

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Mosquitoes do “transfer nutrients from their aquatic larval habitats” to other areas, and serve as food for insects, fish and other animals, he said.

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They also pollinate plants, but this “isn’t well understood and may vary by species”, Peach added.

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Ranson acknowledged there is a valid debate over the ethics of humans committing “specicide”, while pointing out that we are currently unintentionally wiping out a huge number of species.

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– How can it be done? –

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One of the most prominent new technological options is called gene-drive, which involves genetically modifying animals so that they pass down a particular trait to their offspring.

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When scientists tweaked females of malaria-carrying Anopheles gambiae mosquitoes to make them infertile, it wiped out a population in the lab over just a few generations.

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Target Malaria, funded by the Gates Foundation, has tested this technology in several African countries.

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However, the effort was dealt a major blow last year when Burkina Faso’s military-led government ended testing in the country, where it had been criticised by civil society groups and targeted by disinformation campaigns.

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Another strategy involves infecting Aedes aegypti mosquitoes with the bacteria Wolbachia. This can crash their population — or simply reduce their ability to transmit dengue.

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This raises another question: do we actually need to kill them?

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– What if we made them harmless instead? –

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When Wolbachia-infected sterile mosquitoes were released in the Brazilian city of Niteroi, there was an 89 percent drop in dengue cases, research showed last year.

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More than 16 million people across 15 countries have now been protected by these mosquitoes, with “no negative consequences”, Scott O’Neill, founder of the World Mosquito Program, told AFP.

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Meanwhile, a project called Transmission Zero is trying to use gene-drive technology to make it so that Anopheles gambiae mosquitoes no longer spread malaria.

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Lab research published in Nature late last year suggested the scientists are getting closer to this goal, with the team planning to launch an in-country trial in 2030.

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The Burkina Faso setback showed that these projects must have some “political support or buy-in” from the countries where they are tested, study author Dickson Wilson Lwetoijera of Tanzania’s Ifakara Health Institute told AFP.

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– No ‘magic bullet’ –

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Rather than just relying on a technological “magic bullet”, usually funded by the Gates Foundation, Ranson called for a more “holistic solution” for these diseases.

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This would require giving people in disease-hit countries more access to treatment, diagnosis, better housing and better vaccines, she said.

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However, sweeping foreign aid cuts by Western countries have threatened progress against most mosquito-borne diseases over the last year, humanitarian organisations have warned.

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AFP

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