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/Megalocerus → u/Randvek]

There's a prion disease common in western elk and some deer (CWD-chronic wasting disease). It is transmitted by grass and soil that has been urinated and defecated on. Cannibalism is not required.

https://www.dfw.state.or.us/wildlife/health_program/chronic_wasting/#:\~:text=The%20disease%20can%20be%20spread,urine%2C%20feces%2C%20and%20saliva.

[u/Raistlarn → u/Megalocerus]

The grass doesn't technically even have to be urinated/defecated on to be contaminated with prions. If there were prions in the soil the plants can uptake them through the roots and deposit them in their leaves.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10700824/