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疯牛病到底是怎么回事? – 译学馆
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疯牛病到底是怎么回事?

What Happened to Mad Cow Disease?

如果你生在90年代 尤其还居住在英国
If you were around in the ‘90s, and especially if you lived in the UK,
你就记得所有关于疯牛病的恐慌
you might remember all the panic about mad cow disease.
那是从八九十年代以来数千头牛死亡带来的混乱
It’s a disorder that’s killed thousands of cattle since the ‘80s and ‘90s,
以及因它也可以传染给人的说法
and because a version of it can also infect humans,
很多人都真正地吓坏了
a lot of people were really freaked out.
如今 多亏了安全的农场养殖 尽管科学家们仍不知它到底是如何运作的
Today, thanks to safer farming, it probably isn’t anything you need to worry about.
不过你也无需担心任何事
And even though scientists still don’t know exactly how it works,
我们可以确定的一件事是
we can say one thing for sure:
你的牛排真的
Your steak is almost definitely
没有被感染
probably not infected.
音乐
[INTRO ♪]
疯牛病是牛海绵状脑病
Mad cow disease is the common name for a condition called
或BSE的俗称
Bovine Spongiform Encephalopathy, or BSE.
这是一种感染牛的进行性神经性疾病
It’s a progressive neurological disease that affects cows.
随病情发展 它会引起脑和神经系统的损伤
And over time, it causes severe brain and nervous system damage,
最终导致平衡障碍和情绪改变
which eventually leads to trouble standing and walking, and changes in mood,
像进行性躁狂和紧张
like increased aggression and nervousness.
spongiform的意思就是海绵状的
The “spongiform” part of the name just means spongy,
因为传染因子可使牛脑发生海绵状病变
because the infection creates a bunch of holes in the cow’s brain where its cells should be.
1986年 英国首次证实了两例BSE
The first two cases of BSE were identified in the UK in 1986,
但是症状的出现经历了很长的时间
but it takes a really long time for symptoms to show up,
所以科学家们认为首次感染可追溯至70年代
so scientists think the first infections probably date back to the ‘70s.
在1993年的爆发高峰 每周几乎有一
During the outbreak’s peak in 1993, almost a thousand new cattle
千头牛犊感染 但是数据在那之后却戏剧般的下降
were infected each week, but that number has gone down dramatically since then.
BSE是由一种被称为朊病毒的可自我复制的独特的蛋白质引起的
BSE is caused by a bizarre, self-replicating protein called a prion.
其他病原体如细菌和病毒通过DNA完成自我复制
Other pathogens, like bacteria and viruses, use DNA to make copies of themselves,
但朊病毒是细胞膜内正常蛋白质的变异体
but a prion is just a deformed version of a normal protein that’s found in cell membranes.
有时那些蛋白质会游走和变形
Sometimes those proteins can go rogue and get bent out of shape,
但目前这是如何或为什么发生仍不完全明了
but right now, we don’t totally understand how or why it happens.
当蛋白质变为朊病毒时 它们会侵染其他蛋白质
And when proteins become prions, they can bind to other proteins like them
使它们以同样的方式变性
and make them bend in the same way,
然后那些变性的蛋白质又侵染更多的蛋白质
and then those messed-up prions corrupt even more proteins, and so on.
它们在脑和神经系统中大块聚集蔓延
Clumps of them collect and spread in the brain and nervous system,
最终导致脑损害
eventually causing brain damage.
但这需要过程 故症状常在数年后表现
But that takes a while, so symptoms usually don’t show up until years later.
虽然可怕 但BSE开始的方式令人惊骇
All of that is terrible, but how BSE got started is almost as horrifying.
它可能是因为牛犊以
It probably happened because cattle were being fed
羊和其他奶牛的肉骨粉喂养的
ground-up meat and bones from sheep and other cows.

Ugh!
另一种发生在羊身上的朊病毒疾病称痒病
There’s another prion disease in sheep called scrapie,
痒病朊病毒可能通过食物转移至奶牛
and it’s possible that scrapie prions may have jumped to cows
从而导致了这场混乱
through their food and caused this whole mess.
但当任意一个蛋白质折叠错误时BSE也会表现出来
But it’s also possible BSE just showed up when a random protein folded the wrong way.
无论它是如何开始的 小牛的喂养只会使事情更糟
No matter how it started, the cattle feed only made things worse—
因死于BSE的奶牛的骨肉会被研磨
because after cows died of BSE, they were ground up
被喂养于健康的奶牛 所以疾病持续蔓延
and fed to healthy cows, so the disease kept going.
不幸的是 人类也可被感染
Unfortunately, a version of the disease can infect people, too.
人类BSE被称为克雅二氏症
The human version of BSE is called variant Creutzfeldt-Jakob disease,
或vCJD 也是由阮病毒引起
or vCJD, and it’s also caused by bent prions.
虽然我们不能确定它是否因进食污染牛肉引起
We don’t know for sure that it comes from eating infected cattle,
但因为它们都是朊病毒疾病而且在同一时期爆发
but since they’re both prion diseases and both outbreaks happened around the same time,
故大多数科学家认为就是这样
most scientists think that’s the case.
和疯牛病一样 vCJD的症状也会在多年后出现
Like with mad cow disease, the symptoms of vCJD can take years to show up,
一旦症状出现 就进展迅速
but once they do, things move pretty quickly.
脑细胞变性的发生只需数月 症状如下
Brain degeneration happens in just a few months, with symptoms like
战栗 痴呆 行走障碍 甚至昏迷
trembling, dementia, trouble walking, and eventually a coma.
因无治愈方法 患者通常于一年内死亡
Since no cure exists yet, patients usually die within a year.
全球约有230例vCJD
Worldwide, there have been about 230 cases of vCJD,
其中英国就有180例
and about 180 of those were in the UK.
剩下的主要在欧洲 美国仅有4例
The rest were mainly in Europe, and there have been only four cases in the United States,
但它们都是从国外传染而至
but they were all picked up overseas.
90年代开始人类感染率逐渐降低
The rate at which people have been getting infected has gone way down since the ‘90s,
但是科学家将持续研究 因为还有
but scientists will keep studying it because there are other
其他不是由牛引起的克雅二氏症
kinds of Creutzfeldt-Jakob disease not caused by cows.
在认识到疯牛病之前 我们认为CJD是
Before mad cow disease was a thing, we knew about CJD as a rare condition
一种任意蛋白变性就会发生的稀有疾病
that could appear if a random protein went bad,
变性通常由基因突变
usually through an inherited mutation,
或由医疗程序如移植导致
or through medical procedures like transplants.
现在 我们通过给奶牛喂养更安全的食物来降低CJD变异的几率
Today, we keep the risk of variant CJD low by giving cows safer food
并确保我们的牛肉中没有神经系统组织
and by making sure no nervous system tissue gets into our beef.
尽管风险很小 你也不能在美国献血
And even though the risk is small, you also can’t donate blood in the U.S.
也不能在高风险国家停留太长时间 或在
if you spent too much time in high-risk countries or got a blood transfusion
欧洲输血 因为朊病毒也可经血液传播
in Europe, because there’s a chance prions could be spread through blood, too.
最重要的是 新的农业实践真正地使疾病得以控制
Mainly, it’s those new farming practices that have really helped get the disease under control,
且在2016年 英国自疾病爆发以来
and in 2016, there were no new reports of BSE in cows in the UK
首次没有BSE的新报道
for the first time since the outbreak started.
二者都令人兴奋慰藉
Which is both exciting and a relief.
此外 因疯牛病通过神精系统传染
Also, because mad cow disease is transmitted through nervous system tissue,
故没有证据证明你可以从
there’s no evidence you can get it from milk
牛奶或制作汉堡和牛排的肉中感染
or the meat used to make things like hamburgers and steak.
所以你大可不用担心你的烤牛肉
So your roast beef is not out to get you.
这是我们需要了解的
Which is always good to know.
感谢观看本期节目
Thanks for watching this episode of SciShow,
特别感谢斯考特•索雷尔向我们咨询疯牛病
and special thanks to Patreon patron Scott Sorrell for asking us about mad cow disease!
如果你想提交你的问题或喜欢节目
If you’d like to submit your questions or just support the show,
您可以点击partreon.com/scishow
you can do so at patreon.com/scishow.
音乐
[OUTRO ♪]

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视频概述

疯牛病的简介,起源,临床表现

听录译者

收集自网络

翻译译者

【MED】Joye

审核员

审核员W

视频来源

https://www.youtube.com/watch?v=Pxojz6grwcU

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