Name: Why Do Bats Carry So Many Dangerous Diseases?
Uploaded: 2020-03-30T02:44:20.000Z
Duration: 12 min 45 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

One fifth of all mammal species today are bats.

And that's awesome, because they help us out in all sorts of ways.

Like, they pollinate a lot of plants, help regrow forests

and control pests, and their poop is pretty excellent fertilizer.

Some of them can sense magnetic fields, or use sound

to find their food—and, of course, there's the one thing

they all have in common: they can truly fly.

They're the only mammals around capable of powered flight...

But they're also somewhat notorious for something else:

You might have noticed that part, what with all the talk

about zoonotic diseases that's been happening lately.

Those are diseases that are passed to humans from other animals.

And while bats aren't to blame for everything, they have played

a role in the transmission of at least 11 viruses

These diseases aren't the bats' fault, of course.

Research shows that disturbing animal habitats is usually

what causes the transfer of a zoonotic disease to humans.

Still, bats in particular do carry a lot of viruses.

And that's because they have unique immune systems.

Which means we can learn a lot about these pathogens

In fact, bat immune systems are so special

that what we learn from them could someday help us treat

a wide variety of conditions, from cancer to diabetes.

And the kicker is: bats probably have weird immune systems

Unlike gliding, flapping flight requires a huge amount of energy.

So, bats have evolved ways to kick their cellular fuel production

into high gear—mainly, by putting their mitochondria into overdrive.

Those are special compartments within cells that turn food into fuel.

When mitochondria convert nutrients into energy,

they also create byproducts called reactive oxygen species.

So basically, mitochondrial exhaust fumes,

in the form of really reactive molecules which contain oxygen.

to rouse immune cells to action and kill bacterial invaders.

But, they can also cause a lot of damage.

They can weaken cell membranes, mess with proteins,

and even break DNA, and because of that, they play

an important role in diseases like cancer and arthritis.

Cells can try to keep them in check with antioxidants

— compounds that essentially neutralize these overeager molecules.

But those can only do so much, and when the balance gets out of whack,

cells experience a condition called oxidative stress.

This is when most of the DNA damage happens.

So, bats' supercharged mitochondria mean extremely high levels

of oxidative stress—which, in turn, means constantly high levels

But since bats don't immediately get super-cancer

after their maiden flight, researchers have long suspected

they've evolved ways to protect themselves

And a few years ago, genetics studies found mutations

which boost their ability to detect and repair damaged DNA.

Essentially, they've also turbocharged the mechanisms

that prevent genetically damaged cells from replicating.

Which may also explain why they don't seem to get cancers very often.

So, bats produce tons of energy without damaging their cells.

DNA damage can also be a sign of a viral infection,

because viruses need to hijack the cell's genetic machinery to

reproduce, and that process usually involves some strategic snipping.

So, naturally, DNA damage triggers an immune response: inflammation.

Essentially, when cells detect DNA damage or other signs of infection,

they chemically call in white blood cells.

These cells kill and destroy pathogens using a variety

And they also help control how the inflammation unfolds—like,

by bringing in additional white blood cells or switching some of them

from germ-killing to tissue repair once the invasion is over.

This immediate or acute inflammatory response helps to get rid

But remember, thanks to their supercharged mitochondria,

bat cells experience constant DNA damage.

They can repair this damage thanks to those advanced DNA-repair tools.

But the damaged DNA should still light an immune flare

So bats would experience super-inflammation all the time!

And prolonged, chronic, and systemic inflammation isn't so great.

White blood cells and the processes they set in motion

can be really destructive to the body's own tissues.

In short, too much inflammation can lead to organ failure

For one thing, they dampen the activity of STING proteins.

These proteins are one of the ways mammalian cells

trigger an inflammatory response when a virus is detected.

Also, a genetic analysis of multiple bat genomes

showed that they're the only mammals that completely lack genes