Confirmation from here, I felt a voice when I was in the thick of some cleansing last June, 'I hate people so much, I hate them, I hate them!' during a bout of irrational irritation. It was actually kind of a relief, I was able to understand what was going on.
Been pondering it, the Q, are parasites the physical reflection of demons..?
No, they're critters caught up in the corruption of the earth just as much as we've been stuck in it. Book of Jubilees, animals started eating eachother after the Sons of God took advantage of human women (the stronger preying on the weaker).
I don't think parasites would have been a problem in the world as it was originally created.
A lot of the torah is aimed at how to maintain the best health possible, and Jesus brought it all to a head. I feel blessed (though trying to cleanse is hard. )