Originally Posted by 6USMC6
Not necessarily. I was at an event outside Dubois, WY in the mid 80s where half a dozen people drank unfiltered water from a quick little stream full of brookies. Every one of them wound up in the hospital with giardia. If there was a beaver pond, it was several miles up stream. There was a fair sided elk herd up there and a lot of mule deer.
I do carry an MSR filter on bike and hiking trips and use it if there is any question as to the safety of the water (if there is lots of large animal sign around)