Researchers spread transgenic mosquito eggs containing a genetic defect that they transfer to the mosquito population in areas plagued by mosquito-borne diseases, thereby reducing the mosquito population to a considerable extent
Who is the deadliest animal to humans?
Anyone who has visited Africa already knows the answer: the number of people who fall victim to the large prey animals such as lions and tigers is nothing compared to those who kill... the mosquitoes. Some mosquitoes carry malaria parasites and can infect human victims with them. Other mosquitoes - such as Aedes aegypti - spread yellow fever, dengue fever, the chikungunya virus and the Zika viruses. These are not mosquitoes you want to meet in the dark, or at all.
And here is the good news: there is something to be done about these mosquitoes. In fact, a study published on a new method showed that it was able to reduce the mosquito population by 96 percent in the neighborhoods where it was used. And no, these are not traditional insecticides, the kind that also harm the entire environment and undermine the food chain in the area. All the researchers had to do was release genetically engineered mosquitoes - and the rest happened by itself.
But let's start from the beginning.
Brazil may not be found in Africa most of the time, but it still suffers from outbreaks of dengue fever, courtesy of Brazilian mosquitoes. In fact, in the last year the country experienced an almost two-fold increase in the number of people infected with dengue fever. More than 1.1 million Brazilians contracted the disease in the first half of 2022, and about 504 of them died. The World Health Organization included it in the list of "Top Ten Threats to World Health" [1].
The state decided to allow the British company Oxitec to conduct an extensive experiment in its territory, in order to understand how the mosquito population can be reduced. The company focused on four densely populated neighborhoods, which suffer from an especially large number of mosquitoes in their territory. The company's researchers released into these neighborhoods between one hundred and 500 mosquito eggs per resident per week.
This is the moment when you may scratch your forehead and ask - "Why is the solution to mosquitoes actually releasing more mosquitoes into the area?"
The answer is that Oxitec's mosquitoes have been genetically modified with a special defect, which they pass on to all their offspring. The genetically engineered male mosquitoes mate with fertile females in the wild, and these bring forth a large number of eggs. The young larvae hatch from the eggs - then the genetic defect hits the insect. It causes the female larvae to produce in their cells a large amount of a protein known as tTAV. In fact, the cells produce so many such proteins that they fail to produce other proteins that they need to grow. The result is that the females die before they reach puberty. The males, on the other hand, survive and continue to pass on the genetic defect to their offspring as well.
Oxyt scientists assumed that all the transgenic males they released into the wild would compete with the 'natural' males, impregnate the local females - and result in the next generation having almost no adult females. That, at least, was the plan, but biology is a complex matter and surprises abound. This is why a complete and in-depth study must be done - the results of which have only just been published - on such an experiment.
In the study, published in the scientific journal Frontiers in Bioengineering and Biotechnology, the researchers described the methods they used and their results. They found that over the course of the 11-month trial, mosquito populations in the treated areas dropped by an average of 88 percent.[2]. It can be assumed that the few remaining mosquitoes were less dangerous to the population, since only the females attack humans - and there are very few of them left.
Did the decrease in the number of mosquitoes lead to a corresponding drop in the number of people infected with yellow fever, dengue fever and the other evil diseases that the insects unleash on us? This is another question, which the researchers did not try to examine in the current study. In the end, they only wanted to test the effect of the treatment on the mosquito population. From this point of view, genetic engineering seems to have been a resounding success.
And it's also cheap.
Oxitec has already shown that it can reduce mosquito populations in certain areas, but so far it has always released adult mosquitoes. This is the first study to describe the spread of eggs, rather than adult mosquitoes. This may not sound like a big change, but it has dramatic implications. To release adult mosquitoes, the company must first grow the insects in the laboratory, separate the males from the females and release the first ones in the selected neighborhood. This is a process that requires time and costs a lot of money - especially since the separation between the males and females takes place manually.
At some point Oxitec came to the conclusion that it is much easier to work with eggs[3]. All that is needed is to add the eggs to the water - and they do the rest. The females will die on their own, and the males will hatch and go free. In fact, the process is so cheap and simple that Oxitec currently sells 'egg boxes' to businesses and homes, and anyone from the settlement can purchase them - and enjoy genetically engineered insects that patrol around the house and stop the local mosquitoes.
One potential problem with this solution is that we are releasing GMOs into the environment. The genetically modified mosquitoes pass on their defective genes to future generations, and in principle can bring about a long-term change in the characteristics of the population. In reality this does not happen, because the genetic defect itself means that the offspring of the mosquitoes will have difficulty finding fertile females. The males also don't survive long - up to ten days, at most - so they don't manage to spread far.
There are also alternatives to genetic engineering. One of the accepted methods in the past was the large-scale extermination through the use of insecticides. But if you care about the environment, you don't want to spread these materials. They harm all the insects in the area - including those that are important to agriculture and the soul such as bees and butterflies - and can cause an ecological disaster if widely used. And if that's not enough, they can cause health damage in humans in high concentrations. Genetic engineering allows us to reach achievements similar to those of insecticides, but with minimal damage to the environment and the health of the residents[4].
And if you don't want to use insecticides or genetic engineering? So, of course, you always reserve the right to catch the various fevers and die. But I tend to think that most people would rather find a solution to these problems - even if it involves some harm to the environment or mosquitoes - than to let their children die of preventable diseases.
Oxitec showed in the study I described, that the distribution of genetically modified mosquito eggs can reduce the mosquito population in the area by approximately ninety percent. This is not a magic solution. Yes, it is possible to provide residents in developing countries with 'egg boxes', but since the males survive for such a short time, it is necessary to refresh the supply of eggs every week or two. Still, this is wonderful progress, which indicates that we are moving towards a healthier future - and one that involves less damage to the environment.
[1] https://www.who.int/news-room/spotlight/ten-threats-to-global-health-in-2019
[2] https://www.frontiersin.org/articles/10.3389/fbioe.2022.975786/full
[3] Similar to the new Knesset.
[4] https://www.epa.gov/pesticides/following-review-available-data-and-public-comments-epa-expands-and-extends-testing
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