🦟 🇺🇸 🧬 Mosquitoes are a choice

Most Americans think of mosquito-borne diseases such as malaria, yellow fever, and dengue as problems that affect people in other countries, not their own. Until recently, they would have been largely correct: malaria and yellow fever were eliminated in the United States in the twentieth century, and dengue had become extremely rare, with most cases brought back from abroad. But as temperatures have risen and mosquitoes have developed resistance to pesticides, these diseases have become a growing problem again in the United States.

But we don’t have to accept this threat. We have new ways to wipe out mosquito-borne diseases with minimal environmental cost. The United States is sufficiently well-resourced, and its disease-carrying mosquito population sufficiently small, that it can stamp out this problem entirely within its own borders.

The reason we haven’t is that the technology has spent fifteen years in regulatory limbo. Ending this impasse would allow us to eliminate many mosquito-borne diseases from the United States, and eventually the rest of the world.

Genetic engineering can suppress mosquitoes: researchers insert a gene into male mosquitoes that means their offspring will not survive, and then release them into the wild, where they mate with females, prevent those females having any surviving offspring, and collapse local populations. In 2000, biologists at the University of Oxford demonstrated that this idea could work in fruit flies. They engineered the flies to carry a gene that makes a protein called tTAV, harmless in small amounts but lethal when it builds up. In the lab, the insects are reared in a medium laced with the antibiotic tetracycline, which keeps the gene switched off. But, in the wild, where there is no tetracycline, the gene switches on, and the offspring die before adulthood.

The scientists then formed a company, Oxitec, which was intended to work with governments to research and deploy the technology. They engineered the same gene into male Aedes aegypti, the mosquito that spreads dengue and yellow fever. In this strain, the lethal effect is tuned to kill only the female offspring, while the males survive and pass the gene on for a few generations before it disappears. This approach means the gene continues driving down mosquito numbers for several generations without needing a fresh ‘top up’ of engineered males, but it is also self-limiting: the females that inherit it die off each generation, so the lethal gene steadily declines in the wild. Yet the technique is hugely effective. Sustained releases cut a wild Aedes aegypti population in the Cayman Islands by 80 percent, and in a field trial in Juazeiro, Brazil by about 95 percent. The company submitted its data to seek approval in the United States in 2010. But it has been slow going.

Until that point, engineered insects had been used only for agricultural pest control. Since the 1950s, the United States Department of Agriculture (USDA) had been using the ‘sterile insect technique’, sterilizing male insects with radiation rather than genetic modification, which would mate with wild females and produce no offspring, steadily driving the wild population down. The technique’s major success was in fighting screwworm: an extremely nasty insect that lays its eggs in open wounds, and whose larvae then hatch and burrow into the flesh of any animal unlucky enough to be afflicted (usually livestock), killing them within days. The United States used the sterile insect technique to clear out this pest in the 1960s, and eventually pushed it back as far as the southern tip of Panama. This is estimated to have saved American cattle farmers close to $800 million per year, with billions more in benefits to the wider economy. But containment broke, and in June 2026, Texas detected the United States’ first case of screwworm in 60 years, likely aided by cattle smuggling from Central America, where the pest has resurged. With billions of dollars in damages, Texas officials are once again deploying sterile flies to contain its spread.

The Mediterranean fruit fly, which attacks more than 300 kinds of fruit and vegetables and is considered the most destructive fruit pest in the world, has been beaten back the same way, with sterile flies released over California and Florida. It’s estimated that, if the fruit fly resettles in California, the resulting crop damage could cost over a billion dollars per year in that state alone.

⬇️ Continued:
https://worksinprogress.co/issue/mosquitoes-are-a-choice/