Dengue fever: a genetic experiment against mosquitoes

Opinion fever viruses

Experiment with the gene against mosquitoes

Bia Heinemann Mosquito Combo Bia Heinemann Mosquito Combo

Genetically modified mosquitoes released in Florida and Brazil

Image source: Getty Images / SCIENCE PHOTO LIBRARY / SEBASTIAN KAULITZKI, Claudius Pflug

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Dengue and yellow fever: Millions of people are infected with mosquito-borne viruses each year. Experiments now show that genetic engineering can prevent their reproduction. Is this a good idea?

WDuring the past years of the pandemic, life often seemed to be flat. I let time pass and wished to avoid corona infection. Almost unnoticed, experiments have been taking place during this time that are taking the world a huge step forward, making it more resistant to viruses: Oxitec employees released millions of genetically modified mosquitoes in the Florida Keys and in Brazil to see if they would be. Dengue or Zika in the future – the power to stop an outbreak.

The company has now presented the first results, and the experiment has been a complete success: non-biting male mosquitoes (Aedes aegypti) carried the gene that causes all of their offspring to die before they reach sexual maturity. They mated with wild females and indeed the daughter mosquitoes carried the killer gene for them.

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If you leave the experiment running for a while, there will be no more fertile females in the study area – and the population will collapse. In addition, there will be no more gnawing mosquitoes, because only females suck blood. So there will be no transmission of pathogens.

The researchers also explained in a non-peer-reviewed online presentation that the killer genes persisted in the population for three generations (meaning that the descendants of wild-born males also passed them on to their daughters). However, the gene was not found within 400 m from the place of release of the males. This should prove that the method is safe insofar as the gene does not enter the environment unchecked. It must also demonstrate that local outbreaks of dengue or chikungunya can be contained quickly.

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In some countries of the world male mosquitoes (Aedes albopictus(exposed to special bacteria)Wolbachia) are injured. After mating with wild females, these bacteria ensure that eggs do not develop. Here, too, there are reports of success, but there is criticism that the spread of Wolbachia bacteria cannot be adequately controlled.

It has not been demonstrated that the release of genetically or biologically manipulated male mosquitoes significantly reduces the number of cases of dengue, Zika, chikungunya or yellow fever worldwide. Nor has it been demonstrated that such interventions in nature cannot have undesirable consequences for ecosystems.

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All this needs to be checked – and in the US, the next attempt at release is already imminent. In California, Oxitec wants to show that male mosquitoes pass on their killer genes even in climates drier than the swampy Florida Keys.

But now is the time for a little optimism. Each year, more than 100 million people around the world become infected with the fever virus transmitted by mosquitoes, and many more die. But perhaps there will soon be a sure weapon against these viruses.

This article was first published in April 2022.

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