The deadliest animal on the planet responsible for the death of billions -

最も危険な怪物を倒せたら

- the mighty mosquito.

何億人と殺害した 恐ろしい生物

Along with other diseases, it plays host to malaria,

それは蚊だ

one of the cruelest parasites on earth,

蚊はマラリアを持っている

possibly the single biggest killer of humans in history.

残酷な寄生虫であり

In 2015 alone, hundreds of millions were infected.

人類史上最大の殺し屋だ

Almost half a million people died.

2015年だけで ２億人が感染し

A new technology could help us eradicate malaria for ever.

50万人が死んだ

But to do so, we need to engineer a whole animal population.

新技術なら対処できるかもしれない

This is not a hypothetical problem,

だがそれは生物全体を変えてしまう

The modified mosquitoes already exist in a lab.

仮定の話ではなく

Should we use the technology, and is malaria bad enough to risk it?

すでに改造した蚊は存在する

[THEME MUSIC]

この技術を使うべきか

Malaria is caused by a group of micro-organisms.

マラリアはそんなに危険なのか

Plasmodia.

マラリアはマラリア原虫が起こす

Very weird micro-organisms, that consist of just a single cell.

たった１個の細胞からなる微生物だ

They're parasites that completely rely on mosquitoes.

寄生方法は蚊に依存している

Malaria always starts with an insect bite.

感染は蚊から始まる

In its salivary glands, thousands of sporozoites wait until the insect penetrates your skin.

唾液腺の中で

Immediately after invading you, they head for the liver,

蚊が人を刺すのを待ち

where they quietly enter big cells and hide from the immune system.

侵入すると肝臓に向かい

For up to a month, they stay here, in stealth mode, consuming the cells alive and changing into their next form -

細胞に入って免疫系から身を隠す

small, drop-like merozoites.

１ヶ月ほど隠れてすごしたあと

They multiply, generating thousands of themselves,

メロゾイトという形態に変身する

and then burst out of the cells.

そして数千個にまで増殖し

So thousands of parasites head into the bloodstream to look for their next victims -

細胞を飛び出していく

Red blood cells.

血流に乗ると次の犠牲者

To stay unnoticed, they wrap themselves in the membranes of the cells they killed.

赤血球を狙う

Imagine that,

その移動中彼らは

killing someone from the inside,

殺した細胞の膜を被る

and then taking their skin as camouflage.

誰かを殺したあと

Brutal.

その皮を被ってごまかしているのだ

They now violently attack red blood cells,

赤血球に入って増殖すると

Multiplying inside them until they burst, then finding more red blood cells.

飛び出して 次の赤血球を探しに行く

This cycle repeats over and over

これが繰り返される

Pieces of dead cells spread lots of toxic waste material,

壊れた細胞は有毒物質を出し

which activates a powerful immune response causing flu-like symptoms.

これが強い免疫反応を引き起こす

Among the symptoms are high fever, sweats and chills,

高熱に発汗 寒気や頭痛

convulsions, headaches and sometimes vomiting and diarrhea.

嘔吐や下痢を起こすこともある

If malaria reaches the blood-brain barrier, it can cause coma, neurological damage, or death.

脳にまで感染すると昏睡状態となり

The parasites are ready for evacuation now.

最悪の場合 死ぬ

When another mosquito bites the infected human, they get a ride.

攻撃は終わらない

The cycle can start over.

別の蚊が刺せばそこに乗り込む

In 2015, the Zika virus,

そうして続いていく

which causes horrible birth defects if it infects pregnant women,

2015年 小頭症を引き起こすジカ熱が

spread rapidly into new areas around the globe.

新たな地域に広がったが

It too is carried by a mosquito.

これも蚊が原因だ

The mosquito is the perfect carrier for human diseases ,

蚊は病気の優秀な運び屋で

They've been around for at least 200 million years,

２億年前から存在する

there are trillions of them,

数兆匹生息し

and a single one can lay up to 300 eggs at a time.

１匹が１回で300個の卵を生む

They are practically impossible to eradicate,

絶滅がほぼ不可能な

and the perfect parasite taxi.

寄生虫のタクシーだ

But today, we have new revolutionary technology

しかし私たちは現在

that could enable us to finally win the war against them.

新技術を手に入れた

CRISPR.

クリスパーだ

For the first time in human history,

人類史上初めての

we have the tools to make fast, large-scale changes to entire species,

種全体を大規模に変えられる道具だ

changing their genetic information as we please.

遺伝子情報を好きにいじれる

So, instead of attacking isolated groups of insects,

虫を攻撃する代わりに

why not just change the types that transmit diseases?

性質を変えたらどうだろう？

Using genetic engineering,

マラリアに特化した抗体遺伝子を

Scientists successfully created a strain of mosquitos that are immune to the malaria parasite,

蚊の遺伝子に加えることで

by adding a new antibody gene that specifically targets plasmodium.

無害な蚊を作ることに成功している

These mosquitoes will never spread malaria.

この蚊はマラリアを広めない

But just changing genetic information is not enough.

だが改造だけでは十分ではない

The edits would only be inherited by half the offspring,

遺伝子には二つの型があり

because most genes have two versions inside the genome as a fail- safe.

抗体を受け継ぐのは子孫の半分だ

So after just two generations, at most only half of the offspring would carry the engineered gene.

二世代も経れば

In a population of billions of mosquitoes,

その遺伝子は少数派になる

They would hardly make a difference

大量にいる中では効果は薄いだろう

A genetic engineering method called the gene drive solves this problem.

だが遺伝子ドライブなら解決できる

It forces the new gene to become dominant in the following generations,

次の世代に特定の遺伝子を

overpowering the old gene almost completely.

確実に受け継がせる技術だ

Thanks to this twist, 99.5% of all the engineered mosquitoes' offspring will carry the anti-malaria edit.

これで改造した蚊の子孫の99.5％が

If we were to release enough engineered mosquitoes into the wild to mate with normal mosquitoes,

抗体を受け継ぐようになった

The malaria-blocking genes would spread extremely quickly.

こうした蚊を一定量自然界に放せば

As the new gene becomes a permanent feature of the mosquito population,

遺伝子は急速に広まるだろう

plasmodium would lose its home base.

遺伝子は永続的に残るため

Scientists hope that the change would be so fast, they could not adapt to it quickly enough.

マラリアは居場所を失う

Malaria could virtually disappear.

変化が早ければ適応も難しくなり

If you take into account that almost half a million children are killed by it every year,

マラリアは消えるだろう

about five have died since this video started.

マラリアで毎年50万人の子供が死ぬ

Some scientists argue that we should use the technology sooner, rather than later.

動画が始まってから５人だ

The mosquitoes themselves would probably only profit from this.

すぐに使うべきだと言う人もいる

They don't have anything to gain from carrying parasites.

蚊にとっても 寄生虫は

And this might only be the first step - malaria might just be the beginning.

特に必要のない存在だ

Different mosquitoes also carry Dengue fever and Zika

これはまだ最初

Ticks transmit lyme disease,

マラリアは始まりだ

Flies transmit sleeping sickness,

他にデング熱やジカ熱

Fleas transmit the plague.

ダニのライム病

We could save millions of lives, and prevent suffering on an unbelievable scale.

ハエの睡眠病

So,why haven't we done this yet?

ノミのペストがある

For one, CRISPR editing is barely four years old,

私たちは大規模に

so until very recently, we just couldn't do it as fast and easily.

大勢を救うことができる

And there are valid concerns.

だがそうしてはいない

Never before have humans consciously changed the genetic code of a free-living organism on this scale.

まだ新しい技術であり

Once we do it, there is no going back.

そう簡単に実用化はできないからだ

So it has to be done right,

確かな懸念もある

because there could be unwanted consequences if we set out to edit nature

人間は今までこの規模で

In the specific case of malaria though,

自然を変えたことがなく

the risk might be acceptable since the genetic modification doesn't make a big change in the overall genome,

一度やれば もう戻せない

It only changes a very specific part.

間違いは許されない

The worst case scenario here, is probably that it might not work,

悪い結果になる可能性があるからだ

or that the parasite adapts in a negative way.

マラリアの場合は全体ではなく

There is still much debate,

特化した部分を変えるだけなので

Technology as powerful as gene drive needs to be handled with a lot of care.

大丈夫かもしれない

But at some point, we have to ask ourselves,

失敗した場合は 効果がなく

Is it unethical to not use this technology,

悪化するかもしれないが

when everyday, one thousand children die?

議論は尽きない

Humanity has to decide how to act on this in the next few years.

強力な技術は慎重に扱う必要がある

The public discussion is way behind the technology in this case,

しかしこうも問える

What do you think?

技術を使わないことで

This video was made possible in part by viewer donations on patreon.

毎日1000人子供が死ぬのはいいのか

If you want to help us make more videos like this and get nice rewards in return,

数年以内に決断を迫られるだろう

you can do so here.

公的な議論が急がれている

We really appreciate it.

あなたはどう思う？

If you want to learn more about the topic of genetic engineering,

Subtitles by the Amara.org community

we have another video about CRISPR and GMO's.

And in case that's too much biology for you, here's a space playlist.