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Dientamoeba fragilis is probably a non-pathogenic amoebae found in the gut of about 25% of humans.  Its presence has been associated with mild abdominal complains such as diarrhoea, but it is not clear if the amoeba is cause or effect of the upsets. It is between 4-18um and is the only amoeba in the human gut that has two nuclei (this is why its called Dientamoeba), although many cells are mono-nucleate.  It has been suggested that Dientamoeba may have a flagellate stage (Jahn & Jahn, 1949).  Dientamoeba fragilis branches with the Trichomonads in a SSUrDNA analysis (Sogin et al, 1996).  Dientamoeba fragilis does not have a cyst stage and so how the amoeba infects a quarter of the population is something of a mystery, however it has been suggested that the amoeba is carried into the human body within the eggs of the pathogenic nematode Enterobius vermicularis. Fortunately this nematode is easily  eradicated with metronidazole an inhibitor of  microtubules from some species.


Jahn, T.L. & Jahn, F.L. (1949). "How to know the Protozoa". Iowa, Wm.C.Brown Publ.

Sogin, M. L., Silberman, J.D, Hinkle, G. & Morrison, H.G. (1996). "Problems with molecular diversity in the eukarya.".Society of General Microbiology Symposium: Evolution of microbial Life ed.Roberts, D.M., Sharp, P., Alderson, G. & Collins, M.A. Cambridge University Press. pp167-184.

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