Should People Eradicate Mosquitoes?

Find out what might happen to our ecosystems if mosquitoes are eradicated using the technology of gene drives.

More people die from mosquito-borne diseases each year than from any other animal, but only a small portion of the 3,500 mosquito species that exist actually do so. Researchers have been testing gene drives, a type of designed technology that has the potential to eradicate the deadliest insects. Should we therefore get rid of these bothersome insects? Talya Hackett looks into it. Mosquitoes?

Mosquitoes, more than any other species, including other humans, are to blame for more human fatalities each year due to the illnesses they carry. However, only a tiny fraction of the 3,500 mosquito species really cause fatal infections in people. What would it matter if we could get rid of the worst mosquitoes? In the last two decades, scientists have started testing "gene drives," which are man made technologies that theoretically could accomplish that.

Should we then? We need to gain a better understanding of the technology's operation before we can start debating this issue. The genomes of each parent randomly recombine during normal inheritance. So, roughly a 50/50 combination of their parents' DNA is passed on to their descendants. However, gene drives prevent this and make sure they are perpetuated.

Gene drives are present in nature, but scientists have started to manufacture them in closed labs using modern gene-editing technology. For instance, in a 2018 study, scientists gave mosquito embryos a gene drive that, when present in two copies, rendered females sterile. Usually, such a change would be temporary. However, it grew. Some of the transformed mosquitoes' offspring carried the gene. In the offspring's sperm and egg cells, the gene drive that they inherited on one chromosome replicated itself onto the other chromosome to ensure that it was passed on to their progeny, regardless of which chromosome they got.

This cycle repeated as long as there were any men who contained the gene and any females who had one copy, spreading the gene drive. As they progressed, they created more females with two copies of the gene, making them sterile. Because the gene had an almost 100% rate of inheritance, it spread rapidly across the population, and within 12 generations, nearly all females were sterile. As a result, population growth ceased.

With a gene drive that made populations exclusively male in 2020, the same researchers accomplished a comparable result. In the lab, gene drives have been shown to be effective. Due to the advancements made in the fight against diseases spread by mosquitoes, using them in the wild is a significant decision that is being considered. Thanks to current mosquito control measures, such as insecticide-treated bed nets, malaria, the deadliest disease spread by mosquitoes, saw a decrease in mortality between 2000 and 2019. But deaths have started to increase once again.

Since insecticides kill more than just mosquitoes, several mosquito species have evolved tolerances to them. Many see hope in gene drives in addition to the first malaria vaccine ever, which was approved in October 2021. Researchers are investigating what it would look like to use this technology to target only the most deadly mosquito populations. Like Anopheles gambiae, the species that is primarily responsible for the spread of malaria in Equatorial Africa, where the vast majority of fatalities caused by mosquitoes occur, Anopheles gambiae populations influenced by gene drives are predicted to reach a critical mass at which the malaria transmission cycle would be broken. But there are important problems that must be resolved before gene-driven mosquitoes are really released into the environment. For instance, may gene drives stray and lead to the extinction of non-target species?

Although it doesn't appear that many mosquito species interbreed, experts are conducting studies to be sure. And how would the extinction of a mosquito population impact ecosystems? In Ghana, one team is analyzing the feces and stomach contents of insectivores to see how Anopheles gambiae affects the regional food chain. Researchers are also looking into the possibility that population declines can make other insects more vulnerable or open up a space for a potentially dangerous species. Researchers are also looking into alternatives to population decline, such as gene drives that create mosquitoes that are resistant to the parasite that causes malaria. Others are working on solutions to undo the effects of gene drives, if necessary.

In the meantime, others have demanded a halt to gene drive research due to worries about the potential repercussions. Who should make the decision to release gene drives? is yet another issue that this raises. Communities, researchers, authorities, and governments of the nations most impacted by mosquito-borne diseases must play a significant role in the research and decision-making processes. At all levels, discussions are currently taking place to create a structure to handle this novel field of study and the ethical issues it raises.