Several non-pathogenic protozoa inhabit the intestinal. The non-pathogenic protozoa can be divided into two groups: amoebae and flagellates. Protozoa are a diverse group of unicellular eukaryotic organisms, many of which are motile. That can be flagellates, ciliates, and amoebas. During the period 1994-1996, 1,917 children without symptoms, aging between 6 and 10, were studied by means of coprological analysis and Graham method, all of them living in 20 villages in the Guadalquivir valley.The overall prevalence of intestinal parasitism have been of 27.12%. The reported parasites and their prevalence are as follows: Enterobius vermicularis (20.44%), Giardia lamblia (5.05%), Entamoeba coli (2.45%), Endolimax nana (1.61%), Entamoeba histolytica (0.31%), Entamoeba hartmanni (0.05%), Iodamoeba bütschlii (0.05%).
Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Symptoms can range from mild diarrhea to severe dysentery with blood and mucus. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver, as this is where blood from the intestine reaches first, but they can end up almost anywhere in the body. More recent developments include a kit that detects the presence of amoeba proteins in the feces and another that detects amoeba DNA in feces. These tests are not in widespread use due to their expense.