mosquitoes suck. not just literally, theirbites are also itchy and annoying, and certain species transmit parasites and viruses -- likethe ones that cause malaria, yellow fever, and zika -- infecting and killing hundredsof thousands of people every year. and when we told you about the zika virustwo weeks ago, a lot of you had the same question: why don’t we just kill them all? all ofthem! kill all the mosquitoes! humans are historically really good at makingthings 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 mosquitospecies worldwide, and only a couple hundred
of them bite humans. mosquitoes have been around for a lot longerthan people, millions of years, and have survived lots of predators and environmental changes. so that would be a lot of tough insects tokill, and a lot of bug deaths that wouldn’t affect humans at all. and we’ve tried to eradicate mosquitoesbefore, mostly using chemicals that turned out to be awful for both the planet and us,like ddt. but let’s pretend that we were actuallyable to kill all the mosquitoes in some not-environmentally-apocalyptic way. say, if i wished on a star, and the nextday all mosquitoes just poofed out of existence.
would that be so bad for the earth? some scientists actually say no -- that ifmosquitoes 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 mosquitospecies do play important ecological roles. take the mosquitoes that live in the arcticof canada and russia. they fly around in thick swarms and make upa huge part of the biomass there. and these mosquitoes pollinate arctic plants and area major food source for migrating birds. removing these guys -- or other, more southernspecies that are food for fish, birds, and other insects -- could send a ripple throughecosystems, endangering many other plants
and animals. so we probably shouldn’t kill all the mosquitoes. but, we also don’t have to. we know whichspecies are vectors, or carriers, of the worst viruses and parasites that can infect humans. so lots of researchers are currently targetingthese species, and developing ways to kill them, or to kill the dangerous stuff insidethem. take the genus aedes, which transmits lotsof awful diseases. one particularly nasty species is aedes aegypti, which is the primaryvector for the yellow fever, dengue, chikungunya, and zika viruses.
a. aegypti is not just a pest, it’s oneof the most medically significant pests. so it’s the focus of lots of recent experimentsin targeted mosquito eradication. but some of the most promising research doesn’tset out to kill mosquitoes outright -- instead, it genetically modifies them. in 2015, a british company called oxitec createdmale a. aegypti mosquitoes with a self-limiting gene, which basically means that the genecan stop their cells from functioning normally. when these genetically modified mosquitoesare released and mate with females in the wild, the self-limiting gene gets passed onto their offspring. those offspring usually can’t develop properlyand die before they become adults.
no adult mosquitoes means no disease transmission. likewise, a team of scientists in californiainserted modified genes into a species of anopheles mosquitoes, which are vectors forthe parasite that causes malaria. the modified genes cause the mosquitoes tokill the malaria-causing parasites that live inside them, before they can transmit themto humans. and as a bonus, these parasite-destroyinggenes are designed to be passed on to 99.5% of the mosquitoes’ offspring. so, eventually, this entire species couldbe unable to transmit malaria. and scientists think that this same technology could be appliedto other mosquito species, and other parasites
and viruses -- like zika. lastly, some scientists are fighting firewith fire -- or fighting viruses with bacteria -- by intentionally infecting a. aegypti mosquitoeswith a bacterium called wolbachia. wolbachia seems to stop most viruses fromgrowing 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 tobe transmitted to a new person. now, because viruses mutate rapidly, scientistsworry about accidentally creating deadly viruses that are resistant to wolbachia. but a study released this week suggested astrategy to superinfect mosquitoes with more
than one strain of the bacteria at a time. this way, the viruses can’t develop resistanceto the bacteria as easily. and we can keep infecting mosquitoes, to keep them from infectingus. i mean, it’s only fair. so, basically, it would be incredibly difficultand possibly harmful to kill all the mosquitoes. but we may soon be able to focus on certainspecies 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 scishownews.
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