Faecal protozoan (Dientamoeba fragilis) – this is one of the smaller protozoa parasitizing in the human digestive tract. It occurs only in the form of trophozoite and does not produce cysts. The target location is the large intestine. Protozoa do not move outside the digestive tract to other organs. The mode of transmission of infection is not well understood, but the zoonotic nature of the disease is likely. The protozoa enter the human body via the faecal-oral route, probably attached to the eggs of the threadworm.

Dientamoebiasis (a disease caused by Dientamoeba fragilis) occurs all over the world, much more frequently in regions of high population density. If clinical symptoms occur during the course of the infection, they are usually mild and include diarrhea, abdominal pain and lack of appetite, which vary in intensity. Asymptomatic colonization occurs in 75-85% of infected adults, in children symptoms appear in 90% of cases. Symptoms of an acute infection persist for 1-2 weeks. Stools are brown-green, sometimes with mucus. The symptom of a chronic infection is abdominal pain lasting several months. Currently, however, the ability of Dientamoeba fragilis to cause disease symptoms is increasingly questioned.