FENG: Fighting mosquitoes with mosquitoes
Column: Jaded
When you think about the animal that has killed the greatest number of humans in the world, you generally tend to think of large predators. Is it perhaps the great white shark or maybe the cute but deadly hippopotamus? While these animals are certainly deadly, the number of annual fatalities caused by them are eclipsed by the number of individuals killed by the tiny blood-sucking mosquito.
According to the World Health Organization, approximately 725,000 people are killed every year by mosquito-borne diseases. The mosquito has been the center of numerous pathogenic outbreaks over the last couple decades, such as the West Nile virus, malaria and the Zika virus. While conventional control strategies have been employed, these have all failed to stop the spread of these viruses.
To combat this issue, one solution that has been proposed is gene drives. While further testing and research is still required to ensure the safety and efficacy of gene drives, the benefits of this technology far outweigh any potential consequences, lending them to be extremely helpful in the battle against insect-borne diseases.
What exactly is a gene drive? Gene drives are “genetic modification(s) designed to spread through a population at higher-than-normal rates of inheritance.” In most organisms, approximately 50 percent of a creature’s offspring has a copy of the desired gene. In comparison, gene drives copy themselves onto their partner chromosome, so the desired genetic modification is passed onto 100 percent of the offspring.
While the exact science of how this works is a little bit complicated, the key to the system is a protein complex known as CRISPR-Cas9, which is an extraordinarily powerful, efficient, accurate and low-costing genetic modification tool. Not only was CRISPR-Cas9 used by scientists to insert this gene drive into the mosquito genome, but also CRISPR is a key component in the gene drive itself.
This segment allows the gene drive present in one strand of DNA to cut the other copy, leading the normal damaged strand to be repaired with the gene drive as a template and resulting in two copies of the genetic modification. Using gene drives, scientists can insert a gene that renders mosquitoes sterile or infertile that would eventually spread throughout the entire population and cause a massive decline in their numbers.
It goes without saying that the primary benefit of gene drives is how powerful they are. By releasing a couple thousand genetically modified mosquitoes into a given region with a high prevalence for mosquito-transmitted illnesses, you can effectively decrease the mosquito population to a point where their numbers are just too small to infect many people.
More than that, researchers have also developed several built-in “self-destruct” mechanisms into the gene drive. For instance, the daisy drive, which is engineering to specifically lose a link at a time, will gradually run out over the course of several generations. If the gene drive is performing too well and destroying too much of the mosquito population, there is less reason to fear as the gene drive will eventually remove itself from the genome.
There are, of course, numerous fears that opponents of the genetically modified mosquitoes cite. For instance, there are concerns that a gene may spread out of control beyond its intended demographic. If the built-in control mechanisms fail and the entire population of mosquitoes is accidentally killed, there could be a massive disruption of many existing ecosystems.
That said, evidence shows that mosquitoes are not actually an integral part of the ecosystem, and many scientists acknowledge that if all the blood-sucking pests went extinct, there would be little ecological damage.
Many also question whether gene drives would even work in practice. While there have been a large number of controlled trial runs utilizing transgenic mosquitoes, it is hard to say how they may react on a larger scale.
While further testing and research is required to ensure the safety and efficacy of gene drives, they are still an extremely valuable tool that should be implemented in the fight against insect-borne illnesses. While I will admit that I have a bit of a personal grudge against mosquitoes, it is inarguable that the buggers have killed millions across the globe.
With the development of genetic modification tools such as CRISPR-Cas9 and mechanisms such as gene drives, humanity has finally developed the tools to combat them and get rid of these insects once and for all. As with any new technology, there are a number of risks.
But as said by biologist John Cumbers, “We must proceed carefully with new genetic engineering technologies, but we must also weigh the risks of inaction … So what would you rather have: (genetically modified) mosquitoes or dying babies?”
I, for one, would much rather have the modified mosquitoes.
William Feng is a School of Environmental and Biological Sciences sophomore majoring in computer science and bioinformatics and minoring in biochemistry. His column, "Jaded," runs on alternate Wednesdays.
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