Mosquitoes: why can't we just kill all of them?

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It"s impossible to wipe out all mosquitoes, but there are ways to reduce levels regionally

Researchers are working khổng lồ single out species of mosquitoes that spread human disease


nhatroso.com —

The mosquito was never going khổng lồ win any popularity contests, but as the “deadliest animal in the world” spreads the Zika virus, it’s become the target of tough talk và powerful pesticides.

“The mosquito kills more people than any other animal on earth,” Dr. Tom Frieden, director of the Centers for Disease Control & Prevention, told nhatroso.com’s Dr. Sanjay Gupta, this week. “Is there any redeeming feature? … Well, they vị provide food for birds và other insects, but I think the world would be a lot better off without them.”

Indeed, mosquitoes can spread diseases such as malaria, yellow fever, dengue & Zika virus. Even the ones that aren’t carrying diseases are buzzing in ears and threatening everyone’s outdoor fun.

Really, why don’t we just kill all of them?

That solution, it turns out, is the stuff of science fiction.

Aside from the potential impacts on the ecosystem when a species disappears, “it is absolutely impossible to kill all the mosquitoes; it’s just not going lớn happen,” said Roger S. Nasci, executive director of the North Shore Mosquito Abatement District, a public mosquito control program outside Chicago. “No one in the scientific field today has any illusions of being able to lớn eradicate the mosquito.”

The reality is no matter how big of a mosquito-killing effort cities và countries unleash on the pests, “there will always be a remnant population somewhere that will repopulate,” Nasci said.

It’s been tried before

In the not-so-distant past, there were notions of mosquito eradication, but history quickly taught us otherwise.

Nasci points lớn the Herculean job that Latin America undertook in the 1950s & 1960s khổng lồ eradicate Aedes aegypti, the mosquito that transmits yellow fever – and also dengue, chikungunya & Zika. The Pan American Health Organization rolled out all the most effective measures – spraying insecticide such as DDT & discarding standing water containers – on a massive scale. But after efforts let up, the mosquitoes came buzzing right back, possibly hitching a ride on shipping vessels from Asia & Africa.

The United States would probably be hard-pressed lớn achieve the same success if it borrowed Latin America’s strategy khổng lồ wipe out mosquito populations. For starters, the Environmental Protection Agency banned the use of DDT, still the best pesticide to kill mosquitoes, in 1972 because of its devastating environmental effects và possible risks lớn human health. There is also the challenge that mosquitoes develop resistance khổng lồ DDT và other agents such as pyrethrin that limit their effectiveness.

The best hope is khổng lồ limit the number of mosquitoes in an area lớn reduce the risk of disease transmission, Nasci said. There are effective tools for doing so. Nasci và his program turn khổng lồ them when surveillance data show the number of mosquitoes carrying West Nile vi khuẩn – the major mosquito-borne disease in his area, carried by the Culex mosquitoes – is on the rise. His team gets called into action, too, when a fed-up resident can’t enjoy his deck because of all the backyard biters.

The future of mosquito control

The good news is that tools used for controlling mosquito populations wreak less environmental havoc than in the days of DDT – and at least so far have not been associated with resistance in mosquitoes. One approach is khổng lồ spray a formula of bacteria around mosquito habitats. Mosquitoes eat up the bacteria, which then kill them & only them (and related insects) by destroying the lining of their guts.

Another strategy could be to lớn develop tools that only kill the few mosquito species that transmit diseases to lớn people and animals and spare the other 3,000 or so species that don’t vị any harm, said Laura Harrington, professor và chair of entomology at Cornell University.

This plan would involve using genetically modified mosquitoes. It could take several shapes, but one would be to lớn breed male mosquitoes to contain a ren toxic to their offspring. These tweaked males would be released into the wild khổng lồ mate with females, but their larval babies would quickly die off. Studies testing the effect of releases in Brazil và the Cayman Islands have found 80% drops in Aedes aegypti levels. Harrington is also developing genetically modified males that would effectively kill all the females with which they mate.

The downsides of this approach are that genetically modified mosquitoes could be expensive, & they would probably have to be released at least once a year to keep populations in check, Harrington said. It is probably still years before these genetically modified mating menaces are ready lớn join the armamentarium of mosquito control tools, she added.

Learning khổng lồ live with mosquitoes

In the meantime, it is important lớn remember that “mosquitoes can play a very important role in the ecosystem,” Harrington said. They are particularly key in their larval stages when, just because of their sheer mass, they are major food sources for aquatic predators. “If you removed all mosquito larvae in the Everglades, you’d probably have a huge impact,” Harrington said.

For his part, Nasci said his team does not see a “wholesale ecological collapse” when it does mosquito control in the Chicago area, which he would expect to see if the insects played a clutch role in the food chain.

Just because mosquitoes don’t appear to be going anywhere anytime soon does not mean that we must resign ourselves to lớn their biting & buzzing.

There are a number of ways khổng lồ keep mosquitoes at bay. At the most basic level, make sure you don’t have pools of standing water, such as in plant pots or bird feeders, around your home and that your window screens are in good shape.

If you are outside & insects are really making a nuisance of themselves, you can wear bug spray và a long-sleeve shirt, Nasci said. It can also be a good idea to lớn keep an eye any reports of increases in the cấp độ of mosquitoes in your area harboring disease, such as West Nile. Many local public health agencies have monitoring programs, Nasci said.

Even if better mosquito control measures develop – và perhaps one day there are genetically modified mosquitoes – it will still be important khổng lồ mix up approaches, Harrington said.

Even if levels of Aedes aegypti can temporarily be brought down, people should still take personal precautions, such as wearing repellent. And experts need lớn work on developing anti-viral drugs and vaccines against the diseases that that handle of mosquito species carry.