The death toll from diseases carried by mosquitoes is so huge that scientists are working on a radical idea. Why not eradicate them?
Mosquitoes kill more humans than any other animal and were linked to roughly 500,000 deaths in 2015, mostly from malaria. For more than a century, humans have used bed nets, screens and insecticides as weapons, but mosquitoes keep coming back. They are now carrying viruses like Zika and dengue to new parts of the world.
Powerful new gene-editing technologies could allow scientists to program mosquito populations to gradually shrink and die off. Some efforts have gained enough momentum that the possibility of mosquito-species eradication seems tantalizingly real.
“I think it is our moral duty to eliminate this mosquito,” entomologist Zach Adelman says about Aedes aegypti, a species carried afar over centuries by ships from sub-Saharan Africa. It derived from a forest dweller and adapted to thrive among humans, to whom the mosquito spreads at least four viruses that cause major diseases.
Prof. Adelman, a virologist and associate professor of entomology at Texas A&M University, is working to program Aedes aegypti mosquitoes to develop as males.
Eventually, the mosquitoes would run out of mates, crashing the species’ population in places it invaded and “cleaning up a global mess,” he says. Female mosquitoes are the only ones that bite people and transmit viruses.
Purposely engineering a species into extinction—or just diminishing it—is fraught with quandaries. Scientists must weigh the potential impact of removing a species on the environment and food chain. It will take years more research, testing and regulatory scrutiny before most genetically altered mosquitoes can be released into the wild. And the strategy might not work.
Wiping a species off the face of the earth is “an unfortunate thing to have to do,” says Gregory Kaebnick, a research scholar at the Hastings Center, a bioethics research institute in Garrison, N.Y.
He says humans shouldn’t force a species into extinction to meet their own preferences. “We ought to try not to do it,” says Mr. Kaebnick. One justification, he says, would be to avert a serious public-health threat.
Out of more than 3,600 mosquito species, only a few dozen transmit viruses and parasites that can sicken or kill humans. Even the killer mosquitoes pollinate plants and are food sources for other animals, though usually not the only staple, entomologists say.
For decades, agricultural officials have used a “sterile insect technique” to eliminate pests that are dangerous to crops or humans. Insects are sterilized with radiation and then released into the wild.
Insects that mate with the sterilized ones produce no offspring, and the populations die off within a few generations. The technique was used to rid the U.S. and a few other countries of the New World screwworm fly, and it is now being used to battle fruit flies.