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  • Is there a disease that makes us love cats,

    是不是有一種病,會讓我們愛上猫?

  • and do you have it?

    你患有這種病嗎?

  • Maybe,

    也許,

  • and it's more likely than you'd think.

    這病比你想像中的還要厲害。

  • We're talking about toxoplasmosis,

    這就是弓蟲症。

  • a disease caused by toxoplasma gondii.

    這種疾病由弓形蟲引起。

  • Like all parasites, toxoplasma lives at the expense of its host,

    和其它的寄生蟲一樣,弓形蟲吸取宿主的營養,

  • and needs its host to produce offspring.

    生存和繁殖。

  • To do that, toxo orchestrates a brain manipulation scheme

    為此,弓形蟲精心安排了腦部操緃方案。

  • involving cats,

    受到影響的有猫,

  • their rodent prey,

    和他們捕食的囓齒類動物。

  • and virtually all other birds and mammals,

    病毒繼而感染其它鳥類和哺乳類動物,

  • including humans.

    包括人類。

  • Documented human infections go as far back as ancient Egypt.

    最早有文字記載的人類受感染記錄,可追溯到古埃及時代。

  • We found samples in mummies.

    我們在木乃伊身上也發現了弓蟲樣本。

  • Today, about a third of the world's population is infected,

    如今,全球大約有三分之一的人口受到感染。

  • and most of them never even know it.

    大部分人對此並不知情。

  • In healthy people, symptoms often don't show up at all.

    身體健康的人並不會出現受感染症狀。

  • When they do, they're mild and flu-like.

    就算有,也只是類似感冒的輕微症狀。

  • But those are just the physical symptoms.

    但是,那只是身體上的症狀,

  • Toxoplasma also nestles into our brains

    弓形蟲會進駐我們的腦部,

  • and meddles with our behavior behind the scenes.

    在幕後干擾我們的行為。

  • To understand why, let's take a look at the parasite's life cycle.

    不明白?我們來看看寄生蟲的生命週期吧!

  • While the parasite can multiply in practically any host,

    寄生蟲幾乎可以在任何宿主身上裂變繁洐,

  • it can only reproduce sexually in the intestines of cats.

    但弓形蟲只能在猫的腸部進行有性繁殖。

  • The offspring, called oocysts, are shed in the cat's feces.

    它的幼蟲,也叫囊合子,隨猫的糞便排出。

  • A single cat can shed up to a hundred million oocysts.

    一只猫可以排出高達一億的囊合子。

  • If another animal, like a mouse, accidentally ingests them,

    其它動物,像老鼠,不慎吞食了這些糞便,

  • they'll invade the mouse's tissues and mature to form tissue cysts.

    囊合子隨即入侵老鼠的身體組織,成熟後形成胞囊。

  • If the mouse gets eaten by a cat,

    如果猫吃了這隻老鼠,

  • the tissue cysts become active and release offspring

    弓形蟲的胞囊在猫的體內變得活躍,並產下幼蟲。

  • that mate to form new oocysts,

    幼蟲交配後形成新的囊合子。

  • completing the cycle.

    它們的生命就這樣週而復始。

  • But there's a problem.

    問題是:

  • A mouse's natural desire to avoid a cat makes it tough to close this loop.

    老鼠不喜歡接近猫,這是它的天性。

  • Toxoplasma has a solution for that.

    弓蟲症對此有解決辦法。

  • The parasites invade white blood cells to hitch a ride to the brain

    弓形蟲入侵白血細胞,並進入腦部。

  • where they seem to override the innate fear of predators.

    宿主變得無視對天敵的恐懼,

  • Infected rodents are more reckless and have slower reaction times.

    受感染的囓齒類動物動作鲁莽,反應遲緩。

  • Strangest of all, they're actually attracted to feline urine,

    最奇怪的是,它們對猫尿產生好感。

  • which probably makes them more likely to cross paths with a cat

    這讓它們輕易暴露在猫的活動範圍之內,

  • and help the parasite complete its life cycle.

    寄生蟲的生命循環就可以完成了。

  • How does the parasite pull this off?

    它們是怎麼做到的呢?

  • Although the exact mechanism isn't known, toxo appears to increase dopamine,

    精確的機理仍屬未知領域。弓蟲症好像使多巴胺增多,

  • a brain neurotransmitter that is involved in novelty-seeking behavior.

    這是一種使人產生猎奇行為的腦部神經遞質。

  • Thus, one idea is that toxo tinkers with neurotransmitters,

    也許,弓蟲症擾亂腦部神經遞質,

  • the chemical signals that modulate emotions.

    這種化學反應改變了情感。

  • The result?

    結果呢?

  • Fatal attraction.

    這好感可以致命。

  • But mice aren't the only animals that end up with these parasites,

    但是,老鼠並不是惟一因寄生蟲致死的動物。

  • and that's where humans, and all of toxo's other hosts, come in.

    人類,和其它弓形蟲的宿主都是。

  • We can accidentally ingest oocysts in contaminated water,

    誤飲受污染的水,

  • or unwashed produce,

    食用未洗淨的蔬果,

  • or from playing in sandboxes,

    玩堆沙遊戲,

  • or cleaning out litter boxes.

    或清理垃圾時,都會受到感染。

  • This is behind the common recommendation that pregnant women not change cat litter.

    人們常說:孕婦不要清理猫屎箱.這就是原因。

  • Toxo can cause serious birth defects.

    弓蟲症可以引致嬰兒嚴重的先天缺陷。

  • We can also get toxo from eating undercooked meat

    食用未經煮熟的肉類,也有機會感染弓蟲症。

  • from other animals that picked up some oocysts.

    那些動物身上已有弓形蟲幼蟲,

  • And it turns out that toxo can mess with our brains, too.

    當它們長成弓形蟲時,會擾亂我們的腦部運作。

  • Studies have found connections between toxo and schizophrenia,

    研究發現了弓蟲症與精神分裂症之間的相關性。

  • bipolar disorder,

    像躁鬱症,

  • obsessive compulsive disorder,

    強迫性神經官能症,

  • and aggression.

    和攻擊性行為。

  • It also slows reactions and decreases concentration,

    它使人反應遲鈍,專注力下降。

  • which may be why one study found that people involved in traffic accidents

    研究發現,發生交通意外的人,

  • were almost three times more likely to have toxoplasma.

    患有弓蟲症是沒有患病的三倍。

  • So is toxo manipulating our brains as an evolutionary strategy

    弓形蟲逐步適應並控制我們的大腦,

  • to get predatory cats to eat us?

    這會讓捕食成性的猫把我們給吃了嗎?

  • Or are our brains just similar enough to a rodent's

    也許,我們的大腦和囓齒類動物不相伯仲。

  • that the same neurological tricks that lure them in catch us in the net, too?

    同樣的神經官能騙局,誘使他們把我們困在這惡性循環中?

  • And is toxo the reason so many people love cats and keep them as pets?

    是不是因為弓形蟲,才有那麼多人喜歡猫,把牠們當成寶貝?

  • Well, the jury's still out on that one.

    這一問題懸而未決。

  • Some recent studies even contradict the idea.

    一些近期的研究甚至否認這一說法。

  • Regardless, toxoplasma has definitely benefitted from humans

    無論如何,弓形蟲確實從人類中獲益匪淺,

  • to become one of the world's most successful parasites.

    從而成為世上最成功寄生蟲。

  • It's not just our willingness to let cats on our dining room tables

    不只是我們希望猫與我們一同進食,

  • or in our beds.

    或者一同就寢。

  • Raising livestock and building cities which attract rodents

    家畜的飼養和城巿的建設,吸引了囓齒類動物,

  • has provided billions of new hosts,

    為弓形蟲提供了數以萬億計的新宿主。

  • and you and your cat may be two of them.

    你,還有你的猫,就是其中的兩個。

Is there a disease that makes us love cats,

是不是有一種病,會讓我們愛上猫?

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B2 中高級 中文 美國腔 TED-Ed 寄生蟲 宿主 腦部 動物 幼蟲

【TED-Ed】是不是真的有一種病,會讓你瘋狂愛上貓咪? (Is there a disease that makes us love cats? - Jaap de Roode)

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    VoiceTube 發佈於 2016 年 07 月 22 日
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