Mosquitoes: The Extinction Dilemma
Issue 11, Volume 113
By Gary Jiang
It is a warm summer day, and you are pumped to finally go outside and play basketball with your friends. With no schoolwork on your mind, you put on your favorite pair of shoes and step outside. However, instead of being greeted by your friends, you encounter the notorious buzzing of mosquitoes. Soon enough, you will be itching all over and wondering why mosquitoes even exist. Surely the benefits of removing all mosquitoes outweigh the consequences, right?
With the advent of recent gene technologies, gene drives may prove to be the solution to the mosquito crisis. This new advancement will allow certain genes to propagate throughout a population, eventually causing all offspring to carry the artificial gene. Gene drives are cost-efficient and effective, making them a perfect tool to be utilized worldwide. Though the answer to the mosquito elimination question may seem obvious, many factors make it more complicated than it initially appears.
Many people see mosquitoes as merely annoying pests, but in reality, they are the most dangerous creatures on Earth, responsible for 725,000 human deaths per year. The reason for this is not the mosquitoes themselves, but because they carrymany potent diseases. One of these is malaria, the most infamous mosquito-borne disease, which makes up 600,000 of the annual mosquito-caused human deaths. While we live in the United States where malaria is not a risk, other countries, specifically those in Africa, suffer from it. Due to the uneven distribution of wealth throughout much of Africa, some countries cannot afford malaria treatment for their populations. Tropical climates are also perfect for mosquitoes to thrive in, meaning that areas around the equator are most susceptible to their destruction. Non-profit organizations such as the World Health Organization and the World Mosquito Program are actively fighting and supporting mosquito control initiatives around the world in an attempt to suppress malaria once and for all.
Unfortunately, mosquitoes are very efficient. They have a complete life cycle of around eight to 10 days, laying hundreds of eggs anywhere where there is an exposed source of water. They are also unavoidable, as they are tiny and their bite is unnoticeable until the unbearable itching begins. Mosquito bites are performed with an intricate mechanism consisting of six tiny needles, which pierce blood vessels and take any diseases in the blood with them. Using this, mosquitoes can transmit diseases by taking in an infected person’s blood and biting someone else. For example, malaria is caused by parasites in the Plasmodium group carried by mosquitoes. When the mosquito bites, malaria travels through its saliva, entering and attacking the body by residing in the bloodstream and destroying red blood cells. This can lead to symptoms such as anemia, fevers, and chills, with treatment consisting of antiparasitics. Malaria can be lethal if the wrong drug is administered or if it goes untreated.
The two most infamous mosquito species responsible for malaria are Anopheles stephesi and Anopheles gambiae, both of which are native to Africa. Anopheles stephensi is seen as much more deadly than Anopheles gambiae as its behavioral patterns differ greatly from its native counterpart, posing dangers to modern mosquito control methods. Anopheles gambiae cases dropped by 340,000 from 2000 to 2015, but this steep decline has not continued. While Anopheles gambiae targets primarily rural areas, Anopheles stephensi targets urban populations, threatening to spread malaria in densely populated cities rather than in small, local communities. The worst part about this invasive species is how it can thwart modern mosquito control treatments. Anopheles stephensi tends to bite right before people go to sleep, rendering preventative measures like bednets ineffective. This is because they have evolved to counter bednets, giving them the instinct to bite right before nighttime. They also reside outdoors, avoiding indoor insecticides.
Not only is mosquito control extremely expensive, but it can do more harm than good. Common forms of mosquito control include the use of bednets and insecticides. Bednets protect people while they sleep and consist of insecticide-covered nets, while sprayable insecticides actively target live mosquitoes and their larvae. However, insecticides are dangerous for the surrounding environment as they can kill helpful creatures like bees and fireflies. In fact, on average, pesticides reach their target only 0.1 percent of the time. In addition, insecticides and other chemicals are losing effectiveness as mosquitoes slowly develop immunity to them. This is because every so often, a mosquito will have a gene that grants it immunity to certain insecticides, allowing it to easily reproduce and spread that gene to its offspring. As new technology and treatments are constantly being made, the global cost of mosquito treatment continues to grow, reaching an astounding $1.28 trillion from 1970 to 2017.
However, there is a solution to fix all of humanity’s mosquito problems: gene drives. A gene drive is a process that allows scientists to spread certain genes throughout a species. This can be beneficial as gene drives suppress harmful genes, such as those that allow mosquitoes to transport malaria. This is known as an anti-plasmodium transgene, targeting the mosquitoes’ ability to host the malaria parasite. With the development of gene editing technology such as CRISPR, gene drives can be artificially created easily. In a 2018 study, gene drives were used to make female mosquitoes—the ones that bite humans—sterile within a controlled environment. It was successful, leading to all of the females within the mosquito population becoming sterile after 12 generations. With no females able to reproduce, this resulted in a rapid decline in mosquito numbers.
Gene drives are still relatively new and researchers have never purposely wiped out an entire species before. There are many uncertainties with a project of this scale, as mosquitoes are prey for animals in many ecosystems; completely wiping them from the face of the earth would cause drastic changes. A more dangerous creature may absorb the niche, or role, of the mosquito in its ecosystem, and there is no reliable way to gauge the consequences of this. Due to these uncertainties, scientists are attempting to create countermeasures to reverse the process if necessary. But most importantly, there is a moral aspect to wiping out an entire species and “playing God.” If humans can now completely destroy any species they want, what doesthat mean for the future? However, gene drives can also be seen as beneficial because they give scientists the ability to suppress any catastrophically harmful species.
As you swat away mosquitoes from your legs, maybe you are relieved that the end of this pesky bug could soon become a reality. Or, maybe you are concerned about what this project could bring if humans begin to utilize gene drives’ ability to destroy whole populations. As uncertainties are revealed and research improves, mosquitoes and gene drives will mark the start of a new era of gene research.