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GMO mosquitoes: Could genetic engineering protect us from the deadliest animal on the planet?

Zika: Children of the Outbreak
Zika: Children of the outbreak 23:05

Watch the new CBSN Originals documentary, "Zika: Children of the Outbreak," in the video player above.

To some people, the only good mosquito is a dead mosquito. And not just because they can ruin your backyard barbecue.

Mosquitoes have been called the deadliest animals on the planet, transmitting dangerous diseases like malaria, yellow fever and dengue. Millions of people worldwide die each year from mosquito-borne diseases, including half a million from malaria alone.

In the last few years, Zika virus has emerged as the latest health threat carried by mosquitoes. Zika is transmitted by the Aedes aegypti mosquito — and more than half the world's population lives in areas where the species thrives.

But what if we had the technology to eliminate the threat by tweaking the biology of the mosquitoes themselves? Would it be a safer, more effective solution than fumigation or other traditional mosquito control methods? A British company called Oxitec is betting that it will.

Oxitec has developed a method of genetically modifying male mosquitoes so that when they breed with females, the offspring cannot survive. (Only female mosquitoes bite, so handling the males is safe.)

The company has set up test sites and pilot programs in places like Brazil — the country hardest hit by the Zika outbreak — Panama and the Cayman Islands. It has also been negotiating for a pilot program near Key West, Florida, although local opposition has so far hampered the effort.

In 2016, CBS News followed the process in the Brazilian town of Piracicaba, northwest of São Paulo, where researchers were releasing 800,000 genetically modified male mosquitoes a week into a neighborhood with high concentrations of Aedes aegypti. The released mosquitoes were all altered in a nearby lab so that they would need a specific antibiotic to survive. But the antibiotic is not found in the wild, only inside the lab. The released mosquitoes live only long enough to mate, then, without the antibiotic, they die — as do their offspring, who also will now need the same antibiotic to survive.

The company claims an 80 percent reduction in the Aedes aegypti mosquito population in test areas. It is not known if the success rate is long-lasting or what the long-term environmental impact might be. Mosquitoes do have their ecological benefits as a food source for birds, fish, bats and other animals. And some species are pollinators. There is limited research on how reducing mosquitoes might affect the ecosystems, but many ethicists argue that any such sweeping, man-made change is ethically questionable at best.

Despite the controversy, a variety of similar efforts are in the works. Another company, MosquitoMate, is working on a program that introduces a naturally occurring bacteria called wolbachia. When a male mosquito carrying wolbachia mates with a wild female Aedes aegypti, the resulting eggs do not hatch.

And researchers at Rockefeller University are testing a method that introduces human diet drugs, appetite suppressants,  to female mosquitoes. A published study suggests that, when on the diet drugs, the females are tricked into feeling full and lose their attraction to feasting on humans, at least for several days.

In the meantime, health officials say the best way to ward off mosquitoes is by using an EPA-registered insect repellent, such as those with DEET or Picaridin. Check the CDC website for up-to-date information on travel to areas at risk for Zika and guidelines o how to protect yourself, especially if you're pregnant or planning to have a child.

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