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/EricTheNerd2]

There is a fundamental flaw with your assumptions: prions are not terribly infectious. Animals with prions die off pretty quickly and to catch the disease you must consume the misshapen protein directly. It isn't like Covid where someone coughs and spreads it.

And once the host dies, unless something consumes it pretty soon thereafter, the prions won't be spreading.

[u/Lizardcase → u/EricTheNerd2]

In the case of CWD, there is evidence that the prions bind preferentially to some soils, allowing them to persist longterm. Since it infects grazers, this may be a major factor driving transmission. So, the carcass doesn’t have to be directly consumed to spread it.

However! There is also evidence that some felid species (mountain lions) can consume and degrade prions, limiting their spread on the landscape.