how do mosquitoes get zika

we could quite possibly rid the world of disease-causingmosquitoes in the next few years. but… do we want to? i’m anna rothschild and this is gross science. ok so, you’ve probably seen on the newsthat there’s this mosquito-borne virus sweeping through the americas—particularly in brazil.it’s called zika, and in adults it’s usually pretty mild, only causing a rash, red eyes,and some flu-like symptoms. but scientists are starting to see an upsetting relationshipbetween zika virus and birth defects in babies. if pregnant women get the disease, their babiescould be born with something called microcephaly, where their brains and heads are much smallerthan normal. and that can lead to various

cognitive and physical issues. we still haven’t totally established a linkbetween zika and microcephaly, but it’s concerning enough that health officials arewarning women in the affected areas not to get pregnant. and those of us living in unitedstates aren’t necessarily home free. the disease is spread by aedes mosquitoes, whichlive in many parts of the us, too. now, i know this show’s called gross science,but let me just be clear that there’s nothing about the zika outbreak that i find gross.except that mosquitoes are nasty and they carry a lot of diseases. in fact, it seemslike every few years we hear about an emerging mosquito-borne illness. and if you’re likeme, you’re asking yourself, “why can’t

we do something to keep mosquitoes from spreadingdisease? or better yet, “why can’t we get rid of mosquitoes altogether?” well, it turns out that we maybe could. yousee, there’s this new genetic technology called the crispr gene drive that has thepotential to do just that—though it raises some ethical issues. with the crispr genedrive, we can easily insert genes into organisms, like one that would keep mosquitoes from transmittinga certain disease, or would ensure that all baby mosquitoes are born male, which in timewould effectively wipe out the population. now, you’re probably saying, we’ve beengenetically engineering things for years! what’s the big deal? well, most of the time,when we insert a gene into a plant or animal,

the trait it codes for can get diluted outof the population pretty easily, and this happens for a few reasons. to begin with,when we genetically alter an organism, it often lowers its ability to survive and reproduce,so it tends to have fewer babies. also, in most species we get one set of chromosomesfrom our mom and one set from our dad. so, if you mate a modified animal with a wildone, their babies will all have one copy of the modified gene. if all those mate withanimals in the wild, half the babies will carry a copy of the gene. by the great-grandchildgeneration, only a fourth will carry the gene, and so on. you’d have to keep releasinggenetically engineered animals to prevent the gene from all but disappearing.

now, this isn’t a bad strategy. in fact,to combat zika, there are plans in brazil to release genetically modified mosquitoeswhose offspring won’t be able to survive. but, the crispr gene drive does somethingdifferent. when you use it to insert a new gene into an organism, you stick in a littleextra code for an enzyme that can identify any unmodified copies of the gene, too. so,when a chromosome with the crispr gene drive is paired up with one that’s unmodified,the enzyme snips out the unmodified section. then, the cell repairs the chromosome usingthe modified gene as a template. basically, this ensures that every baby of a geneticallymodified organism will have two copies of the gene, for generations to come.

this is an incredibly powerful tool. it hasthe ability to rapidly change whole populations of fast-breeding creatures in the wild. andthe technology is moving quickly, too. scientists only got the crispr gene drive working inyeast at the end of 2014. but they’ve already created a mosquito that’s unable to transmitmalaria. and i spoke with one scientist who said that there’s already collaborationin the works to target one of the mosquito species that carries zika, too. but, no one has released any of these mosquitoesinto the wild yet. a tool this powerful bring up a lot of ethical questions. how comfortableare we with changing whole populations of organisms? or eradicating a species all together?sure, there are thousands of species of mosquitoes,

and the ecological importance of the disease-bearingones is a little unclear. but, it’s still a big decision. and who gets to make it? on the other hand, over 3,000 babies in brazilhave brain damage likely due to zika. and worldwide, about 3.2 billion people are atrisk for malaria. there is a strong ethical case to be made for using this technologyas quickly as possible, too. anyway, this is only an outline on what weknow about zika and crispr, but i’m going to include far more info in the description.and, who knows: your community might needs to be dealing with these ethical issues atsome point in the future. so, please check out those links and then tell me what youthink. i would love to hear your opinions,

so please put ‘em in the comments. alright,see you next week. ew.

Posted by exco

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