It is a middle school math teacher’s favorite trivia question: What is the world’s deadliest animal? After images of a hunting tiger or towering gorilla flash through our imagination, we remember that it is the humble mosquito, whose terrible impact on human lives and healthcare systems is only projected to grow. As carbon emissions continue to rise with no plateau in sight, one oft-forgotten implication of increasing global temperatures is the devastating impact they will wreak on public health, with historically ignored diseases now able to thrive in a new, warmer climate. As global temperatures barrel toward the preferred range for mosquitoes, the number of individuals at risk for contracting malaria and dengue fever may increase by four to seven billion by 2070 relative to 1999.
This threat is already a reality. Take dengue, for example: From 1980 to 1989, there were 1.5 million reported cases globally. Compare that to 2019 alone, when 5.2 million cases were reported. World Health Organization (WHO) officials described this astronomical rise in dengue as a “canary in the coalmine of the climate crisis.” No longer will mosquito-borne diseases primarily threaten equatorial regions—northern cities globally are all at risk due to the rise of Aegypti and Anopheles mosquitoes.
Science: 0. Mosquitoes: 1.
From bed nets to insecticides, progress is being made to combat this terrifying rise. But the current generation of anti-mosquito tools is not aggressive enough to mitigate this deadly problem: Bed nets do little to stop Aegypti, which primarily feed on blood during the day, and toxic insecticides have done little but harm the environment and drive mosquito resistance. In order to save lives from this man-made and mosquito-driven catastrophe, humanity must embrace its most promising scientific technologies: genetic engineering and Wolbachia bacteria, conscious that we are fighting against both Mother Nature and human nature itself.
Scientists have recently discovered a new ally in the fight against mosquitoes: the mosquitoes themselves. One tactic out of this playbook has been injecting the Wolbachia bacteria, which naturally occurs in over 50 percent of the world’s species, into Aegypti mosquitoes. When a Wolbachia-infected female lays eggs, the bacteria prevents the progeny from acquiring and transmitting dengue, chikungunya, and Zika. Moreover, when a Wolbachia-infected male fertilizes eggs, the progeny will not hatch.
Science: 1. Mosquitoes: 1.
The World Mosquito Program (WMP) has embraced this strategy, releasing hundreds of millions of both male and female Wolbachia-infected mosquitoes across 14 countries and protecting an estimated 11 million people as of December 2022. In the dengue-overwhelmed city of Yogyakarta, Indonesia, the release of Wolbachia-infected Aegypti mosquitoes reduced the number of symptomatic dengue cases by 77 percent and hospitalization by 86 percent. These promising results were replicated in Medellín, Colombia, with an observed 95 percent drop in dengue cases. And in Queensland, Australia, dengue was almost completely eradicated.
Science: 2. Mosquitoes: 1.
As with so many silver-bullet climate mitigation solutions, however, success stories fail to paint a full picture. The cost of mosquito-release programs is nearly $15 per person and far more expensive in more rural areas. To blanket the world with Wolbachia mosquitoes, in essence seeking to outcompete the 100 trillion (and counting) existing mosquitoes, is unfeasible. Though mosquito releases should be self-sustaining, scientists discovered that the Wolbachia bacteria weakens mosquitoes, reducing their ability to mate and pass on the Wolbachia infection to the next generation. This has contributed to mosquitoes failing to establish themselves in Vietnam, Malaysia, and Puerto Rico.
Making matters worse, scientists are fighting a dynamic opponent: Mother Nature herself. Given the rapid rates of mutations among arboviruses like dengue, it is not a matter of if, but when, the viruses will evade the protection brought on by Wolbachia—undoing decades of research.
Science: 2. Mosquitoes: 2.
As such, in conjunction with the more restrained Wolbachia approach, we must also turn to one of humanity’s greatest fears: gene editing. Oxitec, a biotech firm, has proven that its gene-drive technology can kill Aegypti without the need for continuous mosquito release. Oxitec designed a kill gene that prevents the survival of female offspring but allows male progeny to survive and reproduce, passing on the kill gene. In Brazil, where Oxitec is commercially approved, the gene drive was linked to a 90 percent reduction in mosquitoes.
Even more thrillingly, University of California scientists designed a gene that prevents the spread of malaria in Anopheles mosquitoes. These scientists have set up a lab on the remote island of São Tomé and Príncipe and are awaiting legal approval to release a colony of their modified mosquitoes. Unlike the WMP or Oxitec approach, the efforts on São Tomé do not just seek to kill off a population of mosquitoes, but rather fundamentally change the genetic makeup of a species.
Science: 3. Mosquitoes: 2.
Rightfully, these Jurassic-Park-esque technologies beg the classic eschatological question: What does it mean to mess with nature? Hesitancy is already circulating on the airwaves, with one Nigerian environmentalist, Nnimmo Bassey, writing of the stalled São Tomé project, “People cannot consent to what they do not understand. They’re just being used as guinea pigs.” In the Florida Keys, Oxitec trials were halted after residents raised concerns about the gene-editing technology. Delusion runs rampant, with suggestions that “Bill Gates’ gene-edited mosquitoes” were responsible for an uptick in malaria cases after a release in Texas—a scientifically impossible feat.
Science: 3. Mosquitoes: 3.
While gene editing is an approach that must be undertaken with caution and proper monitoring, there is no reason to believe that modified mosquitoes pose any great threat to our well-being. Dwelling on future doomsday scenarios will do little to alleviate the catastrophe that we are facing today: 700,000 people die annually from mosquito-borne diseases. To not fight for these lives as best we can would perhaps be the greatest injustice humanity can inflict on itself.
The WMP, Oxitec, and University of California scientists sell a great story, and if they can succeed in eradicating dengue or malaria, it will undoubtedly be one of humanity’s greatest triumphs. But history tells us that it will certainly be a battle: As soon as funding for mosquito releases drops (an incessant risk when it comes to diseases classically associated with the Third World) or research into new dengue or malaria strains is forgotten, progress will stall. Wolbachia bacteria are not the silver-bullet, one-and-done solution that the WMP sells—far from it—and gene-edited mosquitoes will have to constantly change to counter the evolutionary pressure of mutating viruses.
Discovering a potential escape hatch for arboviruses should therefore not be taken to imply that other climate-driven diseases can be ignored or that the public health apparatus is sound. Rather, it should be a wake-up call for the world about the human-induced public health crisis at our doorstep.
We must recognize that the best way to mitigate deaths from this crisis is to prevent outbreaks from happening at all. With months of development required for each release of mosquitoes, no known cures for Zika or dengue, and rising global temperatures, there is little time to waste. It is essential to embrace this opportunity to stymie the rise of dengue and malaria—never forgetting that our savvy opponent is armed with millions of years of evolutionary experience. Despite fears of high costs, failures, and mutant mosquitoes, the time is now to embrace the humble mosquito as a technological weapon.
Science: 4. Mosquitoes: 3. For now, at least.