[crickets] [cymbal plays] [chime] [music plays] [narrator:] brazil, late 2014. [baby cries] doctorsnoticed a disturbing trend. an increasingnumber of babies were born with abnormallysmall heads,
a condition known as microcephaly. the spike in microcephalywas linked to a virus called zika that is spread by mosquitoes. [turchi:]i just never dreamt as an epidemiologistof infectious disease that i would seea congenital transmission by a virus that would dosuch a great damage and would be transmitted by mosquitos.
[mosquito buzzes] [narrator:]throughout the americas, mosquito bites are tiedto many viral outbreaks. in the months before zika spreadin brazil, chikungunya, a tropical virus that causesterrible joint pain, invaded the western hemisphere, infecting almost a million people. and west nile virus sickened more than 2,000 victimsin the u.s.,
with symptoms rangingfrom fever to paralysis. to stop these outbreaks, scientists have turnedtheir attention to fighting the mosquitoesthat carry these diseases. and one of the weapons they areusing is genetic engineering. [narrator:]in south america the zika virus is spreadby a mosquito called aedes aegypti. other diseasesincluding dengue, chikungunya, and yellow feverare also spread
by this persistent insect. [frieden:] aedes aegypti,is the cockroach of mosquitos. it lives indoors and outdoors. it bites day time and night time. it develops a resistanceto insecticides easily. the eggs can overwinterfor a year. to control it, we have to killthe adult mosquitos, the larval mosquitos, both inside and outside.
[narrator:] health officialshave used sprays and screens to protect people from diseases spreadby mosquitoes. but since 2002, scientistsat a biotech company called oxitec have been investigatinga more direct approach: a line of geneticallymodified aedes aegypti mosquitos, called ox513a. [pinto:] the goal of this procedure hereat oxitec is to use our mosquito, ox513a,
to reduce the population numbers of the aedes aegyptimosquito in the wild. [narrator:] when released,these mosquitoes reproduce with wild mosquitoes and cause their offspring to die. although there are concernsabout this technology, authorities have allowedlimited releases to study its efficacy and safety. so how were these geneticallymodified mosquitoes produced?
the process involvedengineering mosquitoes with two new genes. [pinto:] what you do first is create or synthesize the dnayou want to insert. so in our case we usethe two genes that we inserted, the lethality geneand the fluorescent marker. [narrator:] the genes were insertedin the genomes of mosquito eggs. the lethality gene makes the developing mosquitoes dependent
on the antibiotic tetracycline, which is fedto them in the lab, but is not available in the wild. the fluorescent marker geneproduces a protein that glows red when exposed to lightof a certain wavelength. it tells scientists which mosquitoeshave the lethality gene. after the first geneticallymodified mosquitoes grew into adults, scientists bred them in the lab. these mosquitoes passedon the genetic modification
to each new generation, giving rise to a colonyof genetically modified mosquitoes, all dependent on tetracycline. [pinto:]so this is our female room. you can walk in. in these big cages, what we have isour egg producing colony. and in total about12,000 females per cage and they are hereto produce the egg.
so our genetic modificationhas been done in 2002. this change was insertedin the genome of every single of these mosquitoes which are here in this room. they lay their eggson these pieces of paper, all the black little dots are eggsthat have been laid. [narrator:]when scientists plan to release genetically modifiedmosquitoes into the wild, they collect eggsfrom this colony.
they place the eggs in water where they hatch into larvaeand then grow into pupae. at this stage techniciansseparate the males from the females by size. [pinto:] these are the separated females and that's the male pot. [narrator:] the male pupae aresignificantly smaller than the females. feeding them tetracycline,the antidote to the lethality gene, keeps the mosquitos alive
as they grow into adults. [pinto:] so we give an antidotein the lab to the mosquito, so that they don't die and then we go releaseour male into the field. [narrator:]male mosquitoes don't bite people so they will not spread disease. but they live long enoughto mate with female mosquitos. [pinto:] then life becomesexciting for them. they get to dowhat they are best at doing,
which is searching females and copulating with those females and our males will deliver the lethality geneto their children. and in the wild the babies do not come in contactwith the antidote and there they die. [trivellato:] well, here in this van you can fit almost800,000 of male mosquitos.
as we go drivingthrough the area, every time the app beeps we just open oneof these pots in here and the mosquitos will fly aroundand do their job. [narrator:]once released, the genetically modified male mosquitos matewith wild females, and pass their genetic modificationto all their offspring. the male carries two copiesof the genetic modification, so all the offspring inherit
a copy of the lethality gene. the wild offspring willnot feed on tetracycline, the antidote to the gene, and they will diebefore reaching maturity. scientists monitorhow the technique is working by capturing larvae, and determining what percentage havethe tell-tale red fluorescence. studies have shown that,with repeated distribution, the wild mosquito populationof a village
or neighborhoodcan be cut by 95%. if the technique continues to prove effective and safe to humans and wildlife, it could be appliedto other species of mosquitoesand help stem the spread of manydangerous diseases.
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