Giardiasis, or infestation with the protozoan Giardia lamblia, is one of the more common parasitic disorders that afflicts human beings. It can be transmitted through contaminated food or water as well as by direct or indirect contact with body fluids of an infected person. Symptoms, which are usually relatively mild, can include general abdominal discomfort, burping, flatulence, and foul smelling diarrhea. If the infestation is severe, it can lead to problems with the absorption of nutrients. In a previously healthy person, they cause explosive watery diarrhea and abdominal cramping.
Symptoms come on quickly and also resolve quickly, usually about a week van later.
People who have a depressed immune function, such as cancer patients and people who are HIV-positive, crypasthtosporidia pose a particular problem. In these people, the diarrhea is usually more severe and the condition may even become chronic and life threatening. Numerous cases of cryptosporidiosis are believed to have been caused by drinking supposedly safe tap water. There have also been incidents in recent years in which cryptosporidia in ground water have proliferated beyond the so called acceptable point, causing entire communities to be ad vised to either boil their tap water before using it or, preferably, to use bottled water instead. Infection with entamoebas is a more chronic problem, even in previously healthy people.