What If We Killed All the Mosquitoes?


Mosquitoes suck. Not just literally, their
bites are also itchy and annoying, and certain species transmit parasites and viruses — like
the ones that cause Malaria, Yellow Fever, and Zika — infecting and killing hundreds
of thousands of people every year. And when we told you about the Zika virus
two weeks ago, a lot of you had the same question: Why don’t we just kill them all? All of
them! Kill all the mosquitoes! Humans are historically really good at making
things go extinct. So it shouldn’t be too hard to get rid of these bloodsuckers… right? Yeah… not exactly. First of all, there are over 3,000 mosquito
species worldwide, and only a couple hundred of them bite humans. Mosquitoes have been around for a lot longer
than people, millions of years, and have survived lots of predators and environmental changes. So that would be a lot of tough insects to
kill, and a lot of bug deaths that wouldn’t affect humans at all. And we’ve tried to eradicate mosquitoes
before, mostly using chemicals that turned out to be awful for both the planet and us,
like DDT. But let’s pretend that we were actually
able to kill all the mosquitoes in some not-environmentally-apocalyptic way. Say, if I wished on a star, and the next
day all mosquitoes just poofed out of existence. Would that be so bad for the Earth? Some scientists actually say no — that if
mosquitoes were suddenly ripped out of food webs, most ecosystems would heal pretty quickly,
and other organisms would fill in those gaps. But other scientists argue that certain mosquito
species do play important ecological roles. Take the mosquitoes that live in the Arctic
of Canada and Russia. They fly around in thick swarms and make up
a huge part of the biomass there. And these mosquitoes pollinate Arctic plants and are
a major food source for migrating birds. Removing these guys — or other, more southern
species that are food for fish, birds, and other insects — could send a ripple through
ecosystems, endangering many other plants and animals. So we probably shouldn’t kill all the mosquitoes. But, we also don’t have to. We know which
species are vectors, or carriers, of the worst viruses and parasites that can infect humans. So lots of researchers are currently targeting
these species, and developing ways to kill them, or to kill the dangerous stuff inside
them. Take the genus Aedes, which transmits lots
of awful diseases. One particularly nasty species is Aedes aegypti, which is the primary
vector for the Yellow Fever, Dengue, Chikungunya, and Zika viruses. A. aegypti is not just a pest, it’s one
of the most medically significant pests. So it’s the focus of lots of recent experiments
in targeted mosquito eradication. But some of the most promising research doesn’t
set out to kill mosquitoes outright — instead, it genetically modifies them. In 2015, a British company called Oxitec created
male A. aegypti mosquitoes with a self-limiting gene, which basically means that the gene
can stop their cells from functioning normally. When these genetically modified mosquitoes
are released and mate with females in the wild, the self-limiting gene gets passed on
to their offspring. Those offspring usually can’t develop properly
and die before they become adults. No adult mosquitoes means no disease transmission. Likewise, a team of scientists in California
inserted modified genes into a species of Anopheles mosquitoes, which are vectors for
the parasite that causes Malaria. The modified genes cause the mosquitoes to
kill the Malaria-causing parasites that live inside them, before they can transmit them
to humans. And as a bonus, these parasite-destroying
genes are designed to be passed on to 99.5% of the mosquitoes’ offspring. So, eventually, this entire species could
be unable to transmit Malaria. And scientists think that this same technology could be applied
to other mosquito species, and other parasites and viruses — like Zika. Lastly, some scientists are fighting fire
with fire — or fighting viruses with bacteria — by intentionally infecting A. aegypti mosquitoes
with a bacterium called Wolbachia. Wolbachia seems to stop most viruses from
growing inside these mosquitoes. So even if the mosquitoes bite people infected with,
say, the Dengue virus, the virus wouldn’t survive inside the mosquito long enough to
be transmitted to a new person. Now, because viruses mutate rapidly, scientists
worry about accidentally creating deadly viruses that are resistant to Wolbachia. But a study released this week suggested a
strategy to superinfect mosquitoes with more than one strain of the bacteria at a time. This way, the viruses can’t develop resistance
to the bacteria as easily. And we can keep infecting mosquitoes, to keep them from infecting
us. I mean, it’s only fair. So, basically, it would be incredibly difficult
and possibly harmful to kill all the mosquitoes. But we may soon be able to focus on certain
species and take away their ability to infect us, making the world a lot safer. But… not any less itchy. Thanks for watching this episode of SciShow
News. Thank you to all of the people doing this
amazing research. And thank you to our patrons on Patreon who
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