Can we genetically modify pests to make them 're-insects'?

Produced by: Science Popularization China

Author: Wu Yu

Producer: China Science Expo

"The silver candlelight shines coldly on the painting screen, the light silk fan flutters the fireflies...", I was pulled out of the gentle poetry with a "snap" sound, and saw a dead mosquito in my mother's hand. I hurriedly glanced at the stars in the sky, my mother's words still lingering in my ears, but I fell into deep thought: "Mosquitoes are such annoying pests, why can't scientists eliminate them?"

The spring breeze is like old flowers still smiling, and the curiosity of youth is still in my heart. Now is the time to answer the questions I once had. Let us explore the story of humans and mosquitoes, a pest.

Annoying mosquitoes (Photo source: veer photo gallery)

1. The dangerous abyss behind mosquitoes

First, let's ask ourselves a question: Do we really know what pests are? In fact, the answer to the question is quite simple: pests are insects that are harmful to humans.

Yes, anything that is harmful to humans and is an insect can be called a pest. But it seems that it is not that simple, because some insects are harmful or beneficial to humans in different time and space environments. For example, the ants we are familiar with can destroy human food and are harmful to humans, but at the same time, they can also prey on agricultural pests and are beneficial to humans.

Let's turn the story back to mosquitoes. First of all, we all know that mosquitoes can bite people. After biting, their mouth needles will inject a kind of saliva into the skin, which will cause the skin to swell and itch. What's more dangerous is that if there are bacteria, viruses, or parasites in the mosquito's saliva, they will also enter the human body and cause infection. The malaria we often talk about is mainly transmitted in this way. Let me tell you a secret: the blood-sucking mosquitoes are all female mosquitoes.

Pesticides (Photo source: veer photo gallery)

The struggle between humans and mosquitoes can be traced back to two million years ago. Mint, citronella oil, DDT (organochlorine insecticide), DEET (deet), and other eighteen martial arts have been created, and various floral waters and mosquito repellents have almost become our summer must-haves, but these methods seem to be unable to fundamentally eliminate insects. Is it true that scientists have no magical power to "completely" eliminate mosquitoes? Yes, there really is, and that is the famous genetic engineering.

2. Mosquito-killing genetic engineering

Next, let us follow the footsteps of history and see how we humans use genetic engineering, a "martial arts secret", to fight mosquitoes:

Genetic engineering (Photo credit: Biao Xiaozhi)

Wulin Secrets 1.0: In 1974, scientists irradiated 57,000 male mosquitoes to destroy their reproductive ability, and then released them back into Africa, hoping that these sterile male mosquitoes would be able to find female mosquitoes to mate with. Unfortunately, the radiation caused the male mosquitoes' physical condition to deteriorate, and it was difficult for them to successfully mate with female mosquitoes, so this effort failed;

Wulin Secrets 1.1: In 2009, American scientists tried to genetically modify male mosquitoes and released them into towns. After three months, the number of local mosquitoes was reduced by 80%-95%, which was a devastating blow. However, 18 months later, when the research team counted the number of mosquitoes again, they were surprised to find that the number of mosquitoes had rebounded significantly.

This bizarre phenomenon attracted the attention of the research team. After a period of investigation and research, they found that a new type of mosquito had appeared in the area. This mosquito not only overcame the defects brought by genetic modification, but also had super resistance. It was even difficult for people to kill it with pesticides...

Wulin Secrets 1.2: In 2021, a US company called Oxitec will release genetically modified mosquitoes made using more advanced genetic engineering technology into the wild in the Florida Keys, with a weekly release of 12,000 mosquitoes for 12 consecutive weeks. The full trial will be conducted within two years, and a total of 1 billion genetically modified mosquitoes are expected to be released...

Wulin Secrets 2.0: Too advanced to be displayed (maybe it still remains in the brain of a scientist)

Super mosquito (Photo source: Huanqiu.com)

The above is only a small part. In fact, scientists have made a lot of efforts and have developed many "unique martial arts skills". But these unique skills seem to have encountered a problem: the genes of mosquitoes will also mutate in the natural environment. What can we do about this?

3. After Pandora's Box is opened

In the above experiments, there are always a few mosquitoes that survive the attacks of various martial arts. They may become super mosquitoes in the process of reproduction and are immune to all "martial arts", and the consequences of this may be unbearable for humans. What's more, there are more than 3,600 species of mosquitoes recorded in the world. It is really difficult to defeat them all at the same time.

Similarly, if mosquitoes can survive various "martial arts" by changing their own genes, then other pests should be able to do the same. Genetic engineering technology is like a Pandora's box. Humans can open it, but what will jump out of the box after opening it? Do humans have the ability to control the development of events? We don't know these.

Mosquitoes are indeed annoying, but Zhuangzi once said that the world has great beauty but does not speak, the four seasons have clear laws but do not discuss, and all things have their own logic but do not talk about them. As far as we can see now, we have no way to use genetic technology to completely eliminate mosquitoes. Perhaps there is indeed a natural reason for the existence of mosquitoes.

References:

Kyrou K, Hammond AM, Galizi R, et al. A CRISPR–Cas9 gene drive targeting doublesex causes complete population suppression in caged Anopheles gambiae mosquitoes[J]. Nature Biotechnology, 2018, 36.

Page ML . Gene tool could halt malaria spread[J]. The New Scientist, 2018, 239(3197):10.

Felipe J Colón-González, Maquins Odhiambo Sewe, Adrian M Tompkins, et al. Projecting the risk of mosquito-borne diseases in a warmer and more populated world: a multi-model, multi-scenario intercomparison modeling study, The Lancet Planetary Health, 2021, 5, e404.

Fang, Janet. Ecology: A world without mosquitoes.[J]. Nature, 2010, 466(7305):432-434.