Many intestinal protozoa parasites inhabit the gastrointestinal tract of humans. However, majority of them are non-pathogenic commensals or only result in mild disease while a few of them such as Cryptosporidium parvum (CP), Entamoeba histolytica (EH) and Giardia lamblia (GL) are pathogenic and have been associated with human gastrointestinal disorders worldwide among children and adults alike. An analysis was carried out involving 1766 patients observed during the period 2009–2010 and 771 native patients observed during the period 1996–1997A wide variety of intestinal parasites was detected in the study subjects.
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. Asymptomatic human infections are usually diagnosed by finding cysts shed in the stool. Various flotation or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination.