I made my living in the mountains and have seen beaver fever alot.We always used the cold creeks for cooling down beer and pop and take baths sometimes..The beaver fever I have seen has "always" been from drinking contaminated water,not from cooling beverages or bathing although it can happen they say,just never seen it in Idaho creeks.
Boiling the water is #1 for making sure the water is safe..It's not that hard to fill a large metal container and boil it for atleast 1 minute.
Water filters that have at least 0.1 filtration work well..Never seen the fever from anyone using one such as the Sawyer water filters and bottles.I have four myself.I filter creek water into a 5 gallon bucket using the gravity method.
If I was to fill a trailer water tank with creek water just for bathing and dishes it would be treated with bleach...Buying used travel trailers, the first thing I do is sterilize the water tank.
I have never had beaver fever but have paid the price dearly from my co-workers getting it and missing work.Once you have gotten it you will never repeat your mistake again.