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UK biotech firm’s 750 mn GM mosquitoes will mate with females off Florida, sow a deadly gene

Only females of mosquitoes bite and transmit diseases to humans. The female offspring of Oxitec’s genetically modified mosquitoes won't be able to survive.

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Bengaluru: Oxitec, a UK-based biotechnology company, plans to release genetically modified mosquitoes in the Florida Keys islands off the US this month as part of a trial to curb mosquito-borne diseases like dengue and the one caused by the Zika virus. 

This is the latest genetic engineering experiment targeting mosquitoes that is aimed at tackling diseases that continue to kill thousands every year — an approach that has critics as well as backers. 

Only females of mosquitoes bite, while males feed on all nectar. 

The mosquitoes Oxitec plans to release will all be male, carrying a protein that will kill all their female offspring. 

The exact locations where the mosquitoes will be released have not been made public. 

The objective over time is to reduce the population of the Aedes aegypti mosquito, which spreads both the above-mentioned diseases as well as chikungunya and yellow fever. 

Mosquito populations in Florida are believed to have grown resistant to a common group of insecticides, prompting worries. 

Oxitec plans to release around 750 million male mosquitoes to breed with females in the wild over a period of two years. 

While the plan has drawn concern from some environmental groups about its potential impact on ecology, the company says it sees no risk from the experiment. Oxitec claims to have released over a billion genetically modified mosquitoes over the years in other trials.

Also Read: GM mosquito experiment to reduce dengue-causing species in Brazil fails

How transgenic mosquitoes work

There are two approaches to genetically modifying mosquitoes that are being experimented with. One is to modify both males and females to become resistant to diseases, thus reducing their ability to transmit them to other species. 

The other is to modify the reproductive ability of the males so that they either can’t reproduce or only produce sterile offspring. 

The second method aims to lower the population of mosquitoes with the ultimate objective of eliminating them from a region. Since the genetic modification passes from a parent to offspring, it is called “transgenic”, and this is the technology that Oxitec is attempting to test. The first-generation mosquitoes will be called OX513A. 

Oxitec genetically engineers mosquitoes in its UK labs to give them a ‘self-limiting’ gene. The gene will make females dependent on an antibiotic for life — if they don’t get that antibiotic, they will die. 

Eggs laid by these mosquitoes will be shipped to Florida Keys, where they will be soaked in water, which mosquitoes need to hatch. 

When females hatch, they will not have access to the antibiotic and die. But males will survive and carry the gene, which will again kick in when they mate with females in the wild. This is expected to reduce the local female mosquito population. 

The company has already tried the approach in field trials in Brazil, Cayman Islands, and Malaysia. The results were reportedly promising, showing a reduction of up to 95 per cent in mosquito populations and a drop of over 90 per cent in dengue cases in the area. 

Why trials are opposed

Many voices have been raised against the Oxitec trials. Some ecologists say the loss of mosquitoes is not likely to have any long-term consequences on the ecosystem as they are not a keystone species that others depend on, but others claim it is unwise to draw such a conclusion.

The company has also come under criticism for allegedly not being transparent about their and the US regulatory authority Environment Protection Agency’s review process, which Oxitec has rebutted. 

Other critics have flagged the lack of long-term data on reduction of disease, while others still point to the unproven effects of antibiotics in the environment.

There have also been concerns that the experiment may not turn out as it is supposed, as happened in a trial at Brazil, which saw some seemingly sterile offspring reproduce and survive to adulthood. 

The WHO has expressed support for investigating genetically modified mosquitoes as a tool to fight mosquito-borne diseases. “More than 80 per cent of the global population lives in areas at risk of at least one major vector-borne disease. Taken together, these diseases exact an immense toll on economies and can impede both rural and urban development,” the agency said in an October 2020 statement.

It, however, cautioned that the use of the technology “raises concerns and questions around ethics, safety, governance, affordability and cost–effectiveness that must be addressed”. Research into the technology “should be conducted through a step-wise approach and supported by clear governance mechanisms to evaluate any health, environmental and ecological implications”, it said.

(Edited by Sunanda Ranjan)

Also Read: Killer GM fungus helps scientists destroy 99% of malaria mosquitoes in 45 days


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  1. His point is to focus on developing treatment. If we keep continuing playing and damaging nature, Kal Yuga is not far then!!

  2. If I recollect right, this has been tried in the past. Anyhow, this is a good problem solve, hope we can do it here in India – many a vector borne disease will be taken care of.

  3. The West has deep disrespect for life and nature.
    They do not understand that life is deeply interconnected !
    Genetically modifying anything is playing God with nature – and it can cause blowback in ways we cannot imagine !

    It’s best to leave nature alone, respect evolution and natural balance of life ! Dont play with life , put a ban on genetic engineering , because changing one gene, could have effects we do not know !

    • Uhhh, who should respect mosquitoes? They’re a pest. Did you bother to read the article? Mosquitoes aren’t necessary for the environment mentioned in the article. Good riddance to them. But yeah, go ahead and respect the mosquitoes if you want. I’ll be laughing while you get west nile, dengue, and whatever other diseases the mosquitoes give you.

      People have been genetically modifying plants and selectively breeding animals for centuries. These genetically-modified mosquitoes are no different. The ‘risk’ of unknown effects is much better than allowing those pests to survive and continue to spread diseases. If people like you made decisions, polio and other diseases would still be around. I’m glad ration and reason will override half-wits like you.

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