As a family practice doc, I treat skin infections every day, so I thought I would add some insight into this thread and try to dispel some misconceptions.
The vast majority of skin infections are caused by Staph bacteria, with a lesser minority caused by Strep and a tiny handful of other organisms. These bacteria reside on the skin of all of us, and are prevented from causing infections by the barrier of our skin and our host defenses. Occasionally, these bacteria will take advantage of the "opportunity" of an open wound or laceration to circumvent our defenses and cause an infection.
Animal feces and sewage have numerous organisms, but the most numerous by far are the coliform bacteria. These bacteria are common inhabitants of our GI system, and do not typically form skin infections, but rather, cause GI infections(Diarrhea). So by wading in "contaminated" waters we typically are not increasing our chance of skin infections. The reason beaches close when there is a high coliform count is because the act of swimming allows water into our mouths and sinuses which we then swallow and thus seed our GI tract with harmful organisms.
With all that being said, I wouldn't wet wade if there were any open sores on my legs as the water makes an excellent vehicle to carry Staph into your wound from your skin. I believe after 20 years of treating staph infections, I have yet to see someone come in with an infection merely from wading in foul water without some trauma or open access point into the skin.
For me, wet wading a cool stream in the heat of a summer day is one of the greatest pleasures of FF!
