While cattle were blamed as a likely source of Cryptosporidium, the protozoan parasite that caused Milwaukee's 1993 waterborne epidemic, researchers are now convinced waterfowl droppings play a major role in contaminating water supplies.
Recent research indicates ducks and Canada geese can excrete infective crypto into water supplies.
In lab and field studies, waterfowl don't get sick from crypto, yet it passes through their digestive systems intact and is deposited in their fecal droppings. Crypto is a zoonotic disease that affects mainly ruminants, pigs and humans. Infection causes acute diarrhea, dehydration and weight loss despite good appetite. Factors that influence severity of the disease include age at exposure, immune system capability and level of environmental contamination. Cyrpto acute disease usually lasts 3-7 days, but a chronic syndrome can persist for several weeks.