What would happen if scientists had the ability to eliminate diseases transmitted to humans, like malaria?
For years, female mosquito hosts have carried malaria and transmitted it to humans. According to the World Health Organization, this disease caused 400,000 fatalities in 2015 alone.
In 1994, scientists began studying molecular genetics as a way to stop the spread of malaria. Such studies have continued into the 21st century. But, as scientists come closer to eliminating malaria and the insects who carry it, they wonder: would eliminating malaria-carrying mosquitoes be ethical, and what might be the environmental cost?
Specifically, scientists created a gene mutation in female mosquitoes that renders them unable to produce offspring. But critics of this plan, including Andrea Crisanti, a physician and scientist at Imperial College in London who has studied molecular biology for over three decades, suggest that the best way to get rid of mosquitoes is to kill them off—not the malaria parasite within them.
For many years, Crisanti worked with senior research fellow Tony Nolan, along with others in this field, to strategize different ways to eliminate mosquitoes. One of the first strategies this team explored using gene mutation was producing infertile female mosquitoes. The team discovered a significant downside to this process, however: making and mutating DNA is both tedious and grueling. The team also attempted mutating the mosquitoes’ genes to lead to a preponderance of males.
Alleviating some of the stress of Crisanti’s research, University of California-Berkeley researcher Jennifer Doudina and her colleagues invented an innovative new technique for modifying DNA in 2012. For years, researchers have recognized that bacteria contains specific genes that have repeating clusters of DNA. When a virus disrupts bacteria, the bacteria duplicates parts of the virus’ genetic make-up and places these copied genes into the spaces in between the repeated DNA chunks. But the next time the bacteria tries to copy that specific DNA, an enzyme called Cas9 guides RNA—an acid in living cells that carries genetic information—to that gene sequence in the invading virus. This process ultimately removes DNA and fuses the strand back together, only now without the removed DNA segment.
Capitalizing on this process, Doudina and her team showed how to edit any part of a mosquito’s gene quite easily. One year later, Harvard scientist George Church and MIT bioengineer Feng Zhang demonstrated that this strategy could work in living cells.
The Cas9 strategy differs from those previously considered to prevent malaria because it is so accurate and applies universally to living beings. Further, this method brings Crisanti—now considering this research—that much closer to eliminating malaria.
While promising, this strategy presents the possibility for negative and unintended consequences. For example, if mosquitoes are unable to reproduce, the ecosystem and food chain would be seriously and indefinitely altered. Many animals, like birds, eat mosquitoes: if they do not have this food source anymore, they will have to adapt to a more restricted diet. This could lead to a decrease in bird populations. In turn, fewer birds could lead to fewer larger predatory animals, and so on.
Other critics of this research fear that this new type of technology could unleash some unknown, uncontrollable power. Some worry that mal-intentioned people could get their hands on the DNA-altering process and use it to create dangerous epidemics or to infect confidential government documents.
So one is still left with the question: what would be the real cost of driving mosquitoes to total extinction? And is it worth it? In the coming years, researchers including Crisanti could just lead us to find out.