Actually there is a positive anecdote often cited. The Fore people of New Guinea engaged in ritual cannibalism which lead to the propagation of prions across generations. When they stopped, the generations of disease also stopped.
The Fora people even developed a prion that confers resistance to kuru:
> researchers [...] discovered a naturally occurring variant of a prion protein in a population from Papua New Guinea that confers strong resistance to kuru
> This community [...] has developed their own biologically unique response [...] this genetic evolution has happened in a matter of decades
https://en.wikipedia.org/wiki/Kuru_(disease)