itchy red bumps

I have enjoyed reading posts from this site over the last 6 months. I have enjoyed hotspringing since the 1960's and have been to most of the hot springs in Calif., Baja, and Idaho. I even have black and white photos of deep creek with the date l962. One of these I gave to Mike Castro a few years ago and he has it on his wall. There are no trees or aniv. pool.
I am writing to say that ten years ago my three brothers and I revisted the Sespe hot springs (our Dad took us their in the 60's). We camped and soaked for 3 days and all of us complained of severely itchy red bumps that were worse than flea or mosquito bites and lasted for a week. It was so bad that we have never returned. Of the many hot springs I've been in this has never happened before or since. I've seen 2 inch long leeches in the Tub in the long valley when the water was to hot to get in.
I suspect there is some type of parasite or protozoa that can infest warm water that stagnates and isn't washed out by a fresh flow. It was autum that time at the Sespe hot springs and the Sespe river was dry. I would assume that after a good winter wash out deep creek will be clean again.