Ethical dilemma: Should we get rid of mosquitoes? - Talya Hackett

譯者: 穎君 紀 審譯者: 麗玲 辛

Because of the pathogens they carry,

由於蚊子身上帶有病原，

mosquitoes are responsible for more human deaths every year than any other animal,

它們每年殺死的人類數量是動物之冠，

including other humans.

包括人類本身。

But very few of the 3,500 mosquito species

但在三千五百種蚊子裡，只有極少數 真的會傳遞致命的疾病。

actually transmit deadly diseases to humans.

So what if we could get rid of the most lethal mosquitoes?

如果我們能夠消滅 最致命的蚊子，那會怎樣呢？

Over the last two decades,

過去二十年以來，

scientists have begun conducting experiments using engineered technologies

科學家們不斷實驗，

使用基因工程技術「基因驅動」， 理論上能夠消滅最致命的蚊子。

called “gene drives” that could theoretically do just that.

So, should we?

那我們該消滅蚊子嗎？

To begin grappling with this question,

在開始解答這則問題前，

we have to get a sense of how the technology works.

先來了解一下這技術的運作方式吧。

In the usual process of inheritance,

在一般的遺傳過程中，

the genomes of each parent recombine randomly.

親屬的基因會隨機重組，

So their offspring end up with the DNA that’s a rough 50/50 mix

因此父母的基因分別在 子代的基因各佔大約 50% ，

from their parents.

But gene drives thwart this process and ensure they're passed on.

但基因驅動阻擾了這個過程， 保障基因一定會傳下去，

Gene drives are found in nature but,

基因驅動在自然界也觀察得到，

但現在科學家利用新的基因編輯技術，

using new gene-editing technology,

scientists have also begun engineering them in contained labs.

開始在實驗室裡編輯蚊子的基因。

For example, in a 2018 study,

比如說， 2018 年的研究裡，

researchers injected a gene drive into mosquito eggs

研究員將基因驅動注入蚊子蛋裡，

that made females sterile when they had two copies of the modified gene.

讓雌蚊擁有兩套編輯過 的基因，因此無法生育。

Such a modification would usually disappear quickly.

這樣的基因編輯 一般來說很快就會消逝無蹤，

But it spread.

但它反而散播了出去。

The modified mosquitoes passed the gene drive onto some of their offspring.

基因編輯過的蚊子 將這組基因傳到他們的部份子代。

The gene drive, which they inherited on one chromosome,

蚊子們以一條染色體繼承的基因驅動，

copied itself onto the other chromosome in the offspring’s sperm and egg cells,

自我複製到其他染色體上， 和其子代的精、卵細胞裡，

ensuring it was passed on to their offspring,

確保它會被傳承至牠們的子代，

regardless of which chromosome they received.

不管牠們遺傳到哪條染色體。

This process repeated as all males that carried the gene

這個過程在擁有基因驅動的雄蚊，

and all females that had one copy of it, continued reproducing,

和得到基因驅動的雌蚊間 持續重複，兩者繼續繁殖，

spreading the gene drive.

散播基因驅動。

As they did, they produced more females that had two copies of the gene—

牠們繁殖時，就生出越來越多 有兩套基因驅動的雌蚊，

and would therefore sterile.

因此無法生育。

With a near 100% inheritance rate, the gene spread through the population

靠這基因驅動接近 100% 的 遺傳率，它會傳播至整個蚊子群，

and within 12 generations almost all females were sterile,

在 12 代之內，就能讓 幾乎所有的雌蚊不孕，

and the populations crashed.

讓活口的規模大幅下降。

In 2020, the same team achieved a similar result

2020 年，同一批團隊得出同樣的結果，

with a gene drive that made populations male-only.

讓蚊子群裡只剩下雄蚊。

Gene drives have proven powerful in the lab.

基因驅動在實驗室 拿出的成果非常有力。

So, implementing them in the wild is a big decision—

但，要在自然環境裡實行 是個重大的決定──

one that’s being considered because of how the fight

會考慮這個作法是因為 現在對抗蚊媒傳染病的成果不彰。

against mosquito-borne diseases is going.

Existing mosquito control measures, like insecticide-treated bed nets,

現有的蚊媒傳染病防治措施， 如噴了殺蟲劑的蚊帳，

helped reduce the number of deaths from malaria,

減少了瘧疾的染病死亡人數，

the deadliest mosquito-borne disease, between 2000 and 2019.

這是在 2000 到 2019 年 最致命的蚊媒傳染病。

But fatalities have begun rising again.

但死亡人數現今再次上升。

Many mosquitoes have developed insecticide resistance—

許多蚊子開始發展出抗藥性，

and insecticides kill more than just mosquitoes.

且使用殺蟲劑時會影響到其他物種。

In addition to the first-ever malaria vaccine,

第一支瘧疾疫苗

approved in October of 2021,

在 2021 年 10 月獲得核可，

many see promise in gene drives.

也有許多人對基因驅動抱有希望。

Experts are researching what it would look like to specifically target

專家們正在研究如果使用基因驅動技術

the deadliest mosquito populations with this technology.

只消滅最致命的蚊種，會有什麼後果。

Like Anopheles gambiae, for instance:

像是甘比亞瘧蚊，

the species overwhelmingly responsible for spreading malaria in Equatorial Africa,

這個品種是在非洲大陸 傳播瘧疾的罪魁禍首，

which experiences the vast majority of mosquito-related fatalities.

造成蚊媒傳染病導致的大量死亡。

The idea is that, when a gene-drive-affected population

構想是這樣的：經基因驅動改造的 甘比亞瘧蚊群數量減少到一定程度時，

of Anopheles gambiae drops low enough,

it would break the malaria transmission cycle.

就會打破瘧疾傳播的循環。

But before gene drive mosquitoes are actually released into the wild,

但在基因編輯過的蚊子野放之前，

some big questions need answers.

我們還需解答一些重要的問題。

Like, could gene drives cross into and cause the collapse of non-target species?

像是，基因驅動會不會傳給 非目標的物種，導致其滅絕？

It doesn’t seem that many mosquito species interbreed,

蚊子不常與自身以外的品種雜交，

making this unlikely,

所以看似不太可能，

but scientists are conducting research to be certain.

但科學家還在進行實驗，才能確信。

And how might a mosquito population’s collapse affect ecosystems?

另外，一種蚊子的滅絕 會影響生態系統嗎？

One team is examining the feces and stomach contents

有個實驗團隊正在檢驗 迦納國內食蟲動物的排遺和胃內容物，

of insectivores in Ghana to gauge the role of Anopheles gambiae in local food webs.

來觀察甘比亞瘧蚊 在當地食物鏈扮演什麼角色。

And researchers are investigating

研究者們也還在調查

whether suppressing populations could make other insects more vulnerable

壓低某種生物數量的行爲 會不會讓其他品種陷入險境，

or leave a niche open that a harmful species could occupy.

或產生漏洞，讓致命天敵有機可乘。

Scientists are also exploring alternatives to population collapse,

除了壓低數量，科學家 也在尋找其他替代方法，

like gene drives that instead make mosquitoes resistant

像基因驅動方法，但這次是 讓蚊子不再帶有瘧疾病原。

to the malaria parasite.

And others are developing countermeasures to reverse

其他研究員則在研發對抗基因驅動的 反制措施，以備不時之需。

the effects of gene drives if needed.

Meanwhile, some people have called for gene drive research to halt

同時，也有人呼籲停止基因驅動的研究，

out of concern for the possible consequences.

因為他們對潛在的後果有所疑慮。

This raises another question: who should decide whether to release gene drives?

這又帶出另一則問題： 要由誰決定要不要使用基因驅動？

It’s essential that communities, scientists, regulators,

受蚊媒疾病影響最大的社群、 科學家、管制單位，和政府

and governments of the countries most affected by mosquito-borne diseases

be highly involved in the research and decision-making processes.

必須被納入研究及決策過程。

Conversations are currently underway at all levels

現在，各個層面的交流正在進行，

to establish a system to manage this new area of research—

希望建立系統來管理這個新領域，

and the ethical questions it carries.

以及科技所帶來的倫理問題。