How does nature deal with prion diseases?

[u/ProDidelphimorphiaXX]

Wasn’t sure what to flair.

Prion diseases are terrifying, the prions can trigger other proteins around it to misfold, and are absurdly hard to render inert even when exposed to prolonged high temperatures and powerful disinfectant agents. I also don’t know if they decay naturally in a decent span of time.

So… Why is it that they are so rare…? Nigh indestructible, highly infectious and can happen to any animal without necessarily needing to be transmitted from anywhere… Yet for the most part ecosystems around the world do not struggle with a pandemic of prions.

To me this implies there’s something inherent about natural environments that makes transmission unlikely, I don’t know if prion diseases are actually difficult to cross the species barrier, or maybe they do decay quite fast when the infected animal dies.

[u/Randvek]

It’s truly awful, but read about Kuru sometime.

Prions are rare because by far the easiest way to spread the diseases involve cannibalism. This isn’t common in nature and was quite uncommon in civilization as well until modern factory farming techniques started “recycling” animal parts. Mad Cow Disease spreads amongst cows via cannibalism, then humans eat the cannibal cows and get it. Humans don’t spread it to other humans (edit: without eating them).

[u/Emu1981 → u/Randvek]

Prions are rare because by far the easiest way to spread the diseases involve cannibalism.

You can also have prion transmission by eating the brains and spinal cord from organisms that have been infected with a prion that your species is susceptible to (or meat that has been contaminated with those). This is how people get variant Creutzfeldt-Jakob disease from eating beef from cows infected with bovine spongiform encephalopathy (aka mad cow disease).

Humans don’t spread it to other humans.

You can get infected by prions from blood transfusions if you are really unlucky. The biggest issue with prion diseases is that they can remain undetectable for decades before they start causing symptoms. This is why some people from the UK are not allowed to donate blood due to the mad cow disease pandemic back in the 80s/90s (the ban in Australia has recently been lifted).

[u/SirButcher → u/Emu1981]

You can get infected by prions from blood transfusions if you are really unlucky.

This is true, but let's be honest: blood transfusion is not really normal in nature. Most of the time, when humans existed, it was impossible to do such a feat (and survive it).

[u/Jazigrrl → u/Emu1981]

Just to add to this, my grandma died from CJD. She was likely infected from meat in the 80’s during a European cruise and it didn’t appear until 30 years later. The doctors theorize her chemotherapy awakened the infection. Because I am immediate family, and even though they’re 90% sure this was variant CJD, I’m never allowed to donate blood again, or probably donate organs, which sucks.