Once ingested into the warm, dark gut of a new host, stomach acid dissolves the shell, releasing the organisms which attach themselves to the lining of the small intestine and interfere with the body's ability to absorb nutrients and water. The life cycle is completed when the crypto and giardia reproduce in the gut and form new cysts or oocysts which are passed from the body in the feces. Scientists are able to identify several species of cryptosporidium and giardia, and each one seems to prefer a different host. Wildlife is a common source of the giardia found in surface waters, according to Dr. Rebecca Cole, wildlife parasitologist for the National Wildlife Health Center. Crypto is common in dairy herds.
Common manure spreading practices can wash crypto into streams and lakes.
There isn't any effective antibiotic for treating dairy herds, and adults can carry the parasite but not have any of the symptoms. Calves pick up the infection from their mothers and show symptoms for a while, especially diarrhea, but eventually their symptoms disappear too. Although the joint DNR-State Laboratory of Hygiene study was unable to pinpoint a source of the crypto that sickened Milwaukee, unusually high spring runoff conditions in the agricultural lands that are a part of the watershed providing Milwaukee's drinking water are thought to be at least one possible source of the 1993 outbreak. Fighting what we can't see Given the abundance and range of crypto and giardia, it's unlikely they will ever be eradicated from the environment. BMPs may be as economical as planting grassy strips to slow runoff, as simple as changing the timing of fertilizer application, or as involved as building engineered structures, such as water diversions, sediment basins and manure storage facilities.