We used to swim in a natural hot springs pond all the time when I was a kid. I remember a lady that lived close to the pond, telling me that she would never swim in it, because of what all could be in there...and I pooh poohed it. I don't anymore. I've always thought I picked up my flukes mainly in the Pacific Northwest, where they are known to be an epidemic problem in livestock- but I've since "wondered" what all I may have picked up in this pond. We also had a creek that ran behind our house in the N.W- and the kids played in it all the time. I've often thought about it with all of this stuff too. Just up from where they had their swimming hole, it went through our feedlot for cattle :(