Giardia

Giardia is a larger protozoan than Cryptosporidium and while a serious health hazard is not as life-threatening. Its cyst is not as resistant as the oocyst of Cryptosporidium to disinfection. Feces of animals such as beavers are high in Giardia and are sometimes blamed for water-born diseases. Common symptoms are diarrhea, abdominal distention, flatulence, and malaise. Most humans recover, and medication helps.

The source of information was Michael B. Kelly, "The removal of Cryptosporidium by selected drinking water treatment processes", Ph.D. Thesis, Rensselaer Polytechnic Institute, June 1996