Despite their small size, mosquitoes are responsible for more human deaths every year than any other animal, including other humans. This is due to the deadly pathogens they carry. However, only a small fraction of the 3,500 mosquito species actually transmit these deadly diseases to humans. Over the last two decades, scientists have begun conducting experiments using engineered technologies called “gene drives” that could theoretically eliminate the most lethal mosquitoes.
To understand the potential of gene drives, it’s essential to grasp how the technology works. In the usual process of inheritance, the genomes of each parent recombine randomly, resulting in offspring with DNA that’s a rough 50/50 mix from their parents. Gene drives, however, thwart this process and ensure they’re passed on. While gene drives are found in nature, scientists have also begun engineering them in contained labs.
In a 2018 study, for example, researchers injected a gene drive into mosquito eggs that made females sterile when they had two copies of the modified gene. This modification would usually disappear quickly, but it spread. The modified mosquitoes passed the gene drive onto some of their offspring. The gene drive, which they inherited on one chromosome, copied itself onto the other chromosome in the offspring’s sperm and egg cells, ensuring it was passed on to their offspring. This process repeated as all males that carried the gene and all females that had one copy of it, continued reproducing, spreading the gene drive. As they did, they produced more females that had two copies of the gene—and would therefore be sterile. With a near 100% inheritance rate, the gene spread through the population and within 12 generations almost all females were sterile, and the populations crashed.
While gene drives have proven powerful in the lab, implementing them in the wild is a big decision. This is being considered due to the increasing challenge of controlling mosquito-borne diseases. Existing mosquito control measures, like insecticide-treated bed nets, helped reduce the number of deaths from malaria, the deadliest mosquito-borne disease, between 2000 and 2019. However, fatalities have begun rising again as many mosquitoes have developed insecticide resistance. In addition to the first-ever malaria vaccine, approved in October of 2021, many see promise in gene drives.
Experts are researching what it would look like to specifically target the deadliest mosquito populations with this technology. The idea is that, when a gene-drive-affected population of Anopheles Gambiae (the species overwhelmingly responsible for spreading malaria in Equatorial Africa) drops low enough, it would break the malaria transmission cycle. However, before gene drive mosquitoes are actually released into the wild, some big questions need answers.
There are concerns about whether gene drives could cross into and cause the collapse of non-target species. While it doesn’t seem that many mosquito species interbreed, making this unlikely, scientists are conducting research to be certain. There are also questions about how a mosquito population’s collapse might affect ecosystems. Researchers are investigating whether suppressing populations could make other insects more vulnerable or leave a niche open that a harmful species could occupy.
Scientists are also exploring alternatives to population collapse, like gene drives that instead make mosquitoes resistant to the malaria parasite. Others are developing countermeasures to reverse the effects of gene drives if needed. Meanwhile, some people have called for gene drive research to halt out of concern for the possible consequences. This raises another question: who should decide whether to release gene drives? It’s essential that communities, scientists, regulators, and governments of the countries most affected by mosquito-borne diseases be highly involved in the research and decision-making processes. Conversations are currently underway at all levels to establish a system to manage this new area of research—and the ethical questions it carries.
Research the various diseases transmitted by mosquitoes, such as malaria, dengue fever, and Zika virus. Create a presentation that includes the symptoms, affected regions, and current prevention methods for each disease. Present your findings to the class, highlighting the impact of these diseases on global health.
Divide into two groups. One group will argue in favor of using gene drives to control mosquito populations, while the other group will argue against it, focusing on the ethical and ecological concerns. Use evidence from the article and additional research to support your arguments. After the debate, discuss as a class the potential benefits and risks of implementing gene drives in the wild.
Using a computer simulation tool or a simple spreadsheet, model the spread of a gene drive in a mosquito population. Adjust variables such as the inheritance rate and the initial number of modified mosquitoes to see how these factors affect the population over several generations. Share your results and discuss how gene drives could potentially be used to control mosquito populations.
Research alternative methods for controlling mosquito populations and preventing mosquito-borne diseases. These could include insecticide-treated bed nets, vaccines, and biological control methods. Write a report comparing these methods to gene drives, considering factors such as effectiveness, cost, and potential risks. Present your findings to the class.
Role-play a community meeting where different stakeholders (scientists, local residents, government officials, and environmentalists) discuss the potential release of gene drive mosquitoes. Each student will take on a different role and present their perspective on the issue. After the role-play, reflect on the importance of involving various stakeholders in the decision-making process for new technologies.
Mosquitoes – Insects of the family Culicidae, which are known for transmitting diseases such as malaria, dengue fever, and Zika virus. – Mosquitoes are responsible for spreading diseases like malaria and Zika virus.
Gene drives – Genetic tools that can spread a specific gene through a population by increasing its inheritance frequency, potentially modifying or eradicating the population. – Gene drives have the potential to control mosquito populations by spreading genes that make them unable to transmit diseases.
Pathogens – Microorganisms such as bacteria, viruses, or parasites that can cause diseases in their hosts. – Malaria is caused by a pathogen called Plasmodium, which is transmitted by mosquitoes.
Mosquito species – Various types or classifications of mosquitoes based on their physical characteristics and behaviors. – Anopheles Gambiae is a mosquito species known for transmitting malaria.
Inheritance – The process by which genetic information is passed down from parents to their offspring. – In mosquitoes, traits related to disease resistance can be inherited from one generation to the next.
Genomes – The complete set of genetic material (DNA or RNA) present in an organism. – Scientists have sequenced the genomes of various mosquito species to better understand their biology and develop control strategies.
Sterile – Unable to reproduce or produce offspring. – Sterile male mosquitoes are often released in control programs to reduce the population size.
Population – A group of individuals of the same species that live in the same area and can potentially interbreed. – The population of mosquitoes in this region has increased due to favorable environmental conditions.
Malaria – A life-threatening disease caused by the Plasmodium parasite, transmitted to humans through the bite of infected mosquitoes. – Malaria is a major health concern in many tropical regions, leading to millions of cases and deaths each year.
Insecticide resistance – The ability of insects, such as mosquitoes, to survive exposure to insecticides that would normally kill them. – Insecticide resistance is a significant challenge in controlling mosquito populations and preventing the spread of diseases.
