For a long time, Giardia was thought to be a non-pathogenic parasite and was often isolated from individuals without clinical symptoms. However, there has been found a huge bulk of evidence indicating the potential of this parasite for developing disease. Children are more likely to be infected than adults, but different age groups may experience clinical symptoms such as mild diarrhea, flatulence, anorexia, abdominal pain, pain in the epigastric region and ultimately maladaptive syndrome.
Methods: Searches were conducted by two independent researchers in international (PubMed, Web of science, Scopus and Google scholar) and national (SID, Magiran) databases for related studies from the inception of the databases to September 2017 (without time limitation) in English and Persian languages.
Discussion: Giardia has global expansion. In the United States, it is the most common parasitic infection and is the leading cause of epidemic diarrhea caused by water pollution. The same socio-economic factors affecting the spread of Entamoeba histolithic also affect Giardia . Giardiasis should be considered in the differential diagnosis of all cases of "diarrhea in travelers" . The first epidemic of giardiasis caused by contaminated water has been reported in St. Petersburg passengers in Russia. Other short-term epidemics have been reported in the United States and some other places. In general, the points that are relevant to the prevention of ami-bialis also apply to giardiasis contamination. Since studies have shown that Giardia is capable of sustaining the purification and chlorination of water resources, it seems that a better (and perhaps impossible) way of preventing pollution of urban water reservoirs by humans, dogs and mice could be effective.