it is caused by cannibalism, but it can also be caused by eating infected CNS tissue from certain animals.

Prion wasting disease can happen in people (CJD/kuru), cows(mad cow), sheep (scrapie), and deer (zombie deer disease/deer wasting disease). However, in sheep it does not cross the species barrier, and humans cannot contract it from sheep. But you can get it from ingesting infected cow or deer tissue.

So it's not ALWAYS cannibalism, and many of the people who contract it in modern western culture are getting it via infected bovine tissue.