Why mosquitoes bite some people more than others - Maria Elena De Obaldia

譯者: Ng Kai Yuan 審譯者: Adrienne Lin

Some swear they’re cursed to be hunted by mosquitoes

有些人認為自己永遠都是 蚊子眼中的唐僧肉，

while their close-by companions are regularly left unscathed.

與他們同行的同伴都不會被叮上。

But is this an illusion?

但這究竟是不是錯覺？

If it's not, what's going on? And what can we do about it?

如果不是，那又是為什麽？ 我們該如何防蚊呢？

It all comes down to how— and why— mosquitoes find us.

這就要談到蚊子是如何 以及為何要找上我們

While male mosquitoes stick to nectar for sustenance,

雖然雄蚊依靠花蜜維生，

females also seek out blood to provide the nutrients they need for their eggs.

但是雌蚊則尋找鮮血 提供卵所需要的養分。

Different mosquito species evolved to feed on different animals.

不同的蚊子種類 進食的動物種類都不相同。

And, probably within the last 10,000 years,

然而在大約這萬年内，

multiple mosquito lineages independently evolved a predilection for people.

多個蚊子譜系 不約而同發展出對於人類的偏愛。

As human settlements became more permanent,

隨著人類定居時間變得越來越長久，

they provided plenty of standing water, even through intense dry seasons,

即便是在極度乾燥的季節， 居住的環境也會形成積水，

which supported mosquito reproduction year-round.

間接協助蚊子常年的繁衍生殖。

Female mosquitoes are equipped with antennae covered in hair-like appendages

雌蚊的觸角上覆蓋著毛髮狀的附屬物。

that contain odor-sensing receptors and neurons.

這附屬物含有氣味感應受體和神經元，

These pick up on the signals of their preferred hosts,

能夠感應到牠們比較喜歡的宿主。

And over thousands of years,

千年以來，

the mosquitoes that target humans have gotten extremely good at tracking us down.

蚊子追蹤我們人類的技術嫺熟無比。

They also target parts of our bodies where we’re less likely to notice them.

牠們也會叮在 我們較不容易注意到的身體部位。

And they’re sensitive to visual cues and changes in airflow,

對視覺的變化和氣流的變動也很敏感，

so when we try to defend ourselves, they can make swift escapes.

所以當我們嘗試拍死這些害蟲， 牠們能馬上做出反應逃飛，

They even learn to avoid particularly defensive people altogether.

甚至還會乾脆遠離 防禦意識較重的人類。

But before these close encounters happen,

但是在近距離接觸之前，

several factors alert mosquitoes to people's presence.

蚊子能依靠幾項機制 注意到人類的存在。

Female mosquitoes can pick up on the carbon dioxide humans constantly exhale

雌蚊能搜尋到約10米外人類

from about 10 meters away.

持續呼出的二氧化碳。

Once they’ve gotten the CO2 cue,

一旦牠們發現二氧化碳，

they become especially interested in dark, high-contrast objects

就會變得對高對比度的物體（黑點）

and the hues found in human skin.

以及人類的皮膚色階特別感興趣。

As they follow the carbon dioxide plume to its source,

隨著牠們循著二氧化碳的根源飛，

they eventually sense body heat and odors.

會感知到身體散發出來的體熱和氣味。

These smells are generated by the many microorganisms that live on our skin.

這些氣味是由皮膚内的許多微生物產生的。

They break down the secretions our bodies produce, like sweat and sebum.

這些微生物分解我們身體 產生的分泌物，如汗水和皮脂。

In doing so, our skin microbes create smaller organic compounds

在這個過程中，我們皮膚上的微生物 會生成較小的有機化合物，

that can vaporize and get picked up as smells—

揮發成氣味，

smells that human-homing mosquitoes are especially attuned to.

特別吸引以人類為巢的蚊子。

Getting extra sweaty can temporarily make people more attractive to mosquitoes—

流汗期間會更加容易吸引蚊子

as can ingesting alcohol or being pregnant.

攝取酒精或懷孕也有同樣的效果。

And the Plasmodium parasite that causes malaria

被瘧原蟲感染瘧疾的人們，

makes the people it infects more appealing to mosquitoes by increasing

會增加皮膚上某些 散發水果香氣的醛類化合物數量，

the amounts of certain fruit-smelling aldehyde compounds on their skin.

變得更加容易遭蚊子的叮咬。

This is extremely helpful to the parasite

這對瘧原蟲極其有利，

because it depends on both humans and mosquitoes to reproduce.

因為牠們繁衍的媒介就是人類和蚊子。

But in addition to these temporary factors,

除了這些暫時性的因素外，

about 20% of people are thought to be naturally high attractors,

約20%的人天生比較容易吸引蚊子

or mosquito magnets,

或者稱為“蚊子磁鐵”，

who are disproportionately targeted year after year.

這些人每年遭受不成比例的襲擊。

If you’re one of them, you’re probably well aware.

如果你是這20%中的其中之一， 那你應該早就發現了。

Sorry about that.

為此我感到抱歉。

Why this is seems to come down to some skin-specific characteristics.

這歸咎於一些特定的皮膚特徵。

While carbon dioxide exhalations and body heat consistently signal the presence

雖然呼出的二氧化碳和體溫 一直都是暖血動物

of warm-blooded animals,

存在的信號，

human body odor is more distinctive.

但人體的氣味比較容易被區別。

And everyone hosts different microbial communities on their skin,

每個人的皮膚上 都寄生著不同的微生物群落，

which contribute to unique body odors that likewise vary from person to person.

會產生獨特的體味，味道因人而異。

Researchers reveal that the receptors mosquitoes use to detect acidic compounds

研究人員揭示， 蚊子用來檢測酸性化合物的感受器

are especially important in helping them navigate towards humans.

是幫助牠們導向人類至關重要的工具。

And, indeed, humans with more abundant skin acids

已被證實，皮膚排出更多酸性物質的人

prove to be consistently more attractive to mosquitoes.

長期以來確實對蚊子更加具吸引力。

Because it’s such a persistent trait, certain genes may play a role,

因為這特徵幾乎伴隨著一生， 基因應該是其中的關鍵，

perhaps by helping determine the skin’s microbial composition.

或許決定了皮膚的微生物組成。

Scientists have observed that mosquitoes demonstrate similar levels of attraction

科學家透過觀察發現所有的同卵雙胞胎

among identical twins while responding more variably to fraternal twins,

對蚊子的吸引力大同小異, 而異卵雙胞胎則大相徑庭，

which supports that there may be some genetic basis at play.

這項發現支持了容不容易被蚊子叮 可能與基因有關係。

But beyond confirming that mosquitoes are, in fact,

已經很確定的是，蚊子

conspiring against some of us specifically,

會在暗地裡密謀要襲擊的對象是誰，

understanding what makes people mosquito-magnets

所以清楚知道牠們作案對象的喜好，

has serious, large-scale implications.

對我們意義重大。

Every year, hundreds of thousands of people die from mosquito-borne diseases.

每年，有幾十萬人死於蚊媒傳染病，

And resources aren’t reaching those who need them most.

而拯救資源卻沒到最需要的人手上。

This knowledge can help inspire solutions, like more effective insect repellents

這知識可以幫助啓發制訂預防方案， 比如更有效的驅蟲劑

that manipulate the skin's microbiome and odors.

調節皮膚的微生物群落和氣味。

And knowing that some people are especially strong mosquito attractors

而且知道哪些人是蚊子吸引器

could also help efforts to get them resources

也能給予他們防蚊資源

like repellents, bed nets, vaccines, tests, and treatments.

像驅蟲劑、蚊帳、疫苗，試驗、藥物。

The results could not only be less itchy,

這些工具不僅能止癢，

they could break transmission cycles and save countless lives.

還能打破傳染病傳播的規律 拯救無數無價的生命。