Although I have already commented on this thread in the past, I feel compelled to toss in another 2 cents.
YES, the bacteria in all bodies of fresh water are the same. The difference is in levels. E, coli and other fecal coliform bacteria are ubiquitous in fresh water. They are even in your drinking water, only a levels so low as to be considered not a health hazard. The pathogenic levels in a pond, whether natural or man-made will be determined by its immediate environment and the animal (including human) immersion load. In addition, there are other parasitic organisms that can trigger major health issues in humans.
I would, at least, be prepared to conduct periodic biological water testing to monitor pathogen levels.
Most people involved in the Water Feature industry will wear protective clothing, wader and gloves, when performing any in-pond maintenance. Why do you think this is?
"Everybody is ignorant, only on different subjects." - Will Rogers