Years ago, like when mad cow disease first hit Europe, I read a really interesting article in either Time or Newsweek on a theory of where it originated. The article laid out a theory that I thought as fascinating as it was yucky.
In England, they were commonly using bone meal to supplement cattle feeds, however since this was such a popular idea at the time, the price of bones went up high enough to where they needed to start importing bones/bone meal. India was the country that stepped up to the plate with a supply of bones. Rewind a little here and remember that in India there are religions (especially Hinduism) that hold cows in high esteem. So when your favorite bovine passes, they would place the animal in the river as their religion suggests. This created large deposits of bones in the river systems of India. Some capitalist decided that they could basically mine/dredge these bones out of the rivers and sell them to English feed makers.
The yucky part is that Hinduism also allows some humans to also be treated to a river burial. I guess even though India banned river burials at some point, there were still documented occurrences of human bones making it into the bone meal supply chain. And just by chance, one of the areas in India where they were harvesting these bones is a known hotspot for human cases of TSE. So the whole articles point was that we have just witnessed the infecting of our own food supply with TSE causing prions that originally came from the human bones of a TSE infected person in India that crossed over to bovines.
