AUDIE CORNISH, HOST:
The explosive growth of the Zika virus highlights the need for better ways to control mosquitoes. As we just heard, there's repellent and netting. Now add genetic engineering to the mix. NPR's Joe Palca reports on a company that is testing it for his series Joe's Big Idea about innovative solutions to tough problems.
JOE PALCA, BYLINE: The company is called Oxitec. It's based in Oxford, England. Oxitec has genetically engineered male mosquitoes so that their offspring don't survive. Haydn Parry is Oxitec's CEO.
HAYDN PARRY: Every single time one of our males mates with a female, all those offspring will die. So if we can make sure that more of our males are mating those females, we actually crash that population.
PALCA: No mosquitoes, no disease transmission. The Zika virus is transmitted by a mosquito called Aedes aegypti. Parry says they've tested their approach in field trials.
PARRY: And in every trial, we've reduced the population of Aedes aegypti in the area that we've been releasing by over 90 percent in about six months. So it's really very effective.
PALCA: Parry says they've been releasing their genetically modified mosquitoes in the Brazilian town of Piracicaba since last May, and he says the mayor of Piracicaba recently asked the company to expand its efforts. Despite initial success there, Perry says it's miserably hard to completely eradicate Aedes aegypti from an area.
PARRY: You will find mosquitoes will come back into an area over time. They'll hitchhike in through cars, etc. So you - once you got your control and you've reduced it by 90 percent or more, you need to consolidate your winnings, if you like.
PALCA: That means you have to keep releasing the genetically modified male mosquitoes in the affected area. And even a 90 percent reduction in mosquitoes might not be good enough to end a disease outbreak. For example, in Singapore, they were trying to control the same mosquito because it also carries a virus called dengue. Just reducing the population wasn't good enough to stop the spread of dengue. Anthony James is a mosquito-borne disease expert at the University of California, Irvine.
ANTHONY JAMES: The challenge is that it doesn't take that many mosquitoes to have a dengue epidemic. That's the problem. And when we learn that - in Singapore, where they went and reduced the number of mosquitoes per household significantly, but they're still having epidemics.
PALCA: It's too soon to say whether you need complete eradication to stop the spread of the Zika virus. Some environmental groups have raised objection to Oxitec's plans. They worry about the possible unintended consequences of unleashing a genetically modified mosquito, even one that's supposed to die out. But Irvine's Tony James thinks the risks are negligible, and he thinks Oxitec's approach is sound.
JAMES: I'd be intensifying the efforts, you know, to see if I can get rid of those last single-digit percentages and stuff.
PALCA: The emergence of the Zika virus makes intensifying efforts seem like an idea worth considering. Joe Palca, NPR News.
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