Case #207 – July, 2007
This was a case of giardiasis caused by Giardia duodenalis. Also shown were cysts and trophozoites of Entamoeba hartmanni, a nonpathogenic amoeba. Diagnostic features were:
- the shape of the Giardia cyst (blue arrow, Figure A), and the presence of fibrils (green arrow, Figure A) and intracystic bodies (red arrow). Three nuclei were faintly visible as well. Follow-up email communication with the submitter confirmed the size to be about 10 micrometers in length.
- cysts of E, hartmanni that had four or less nuclei and rounded chromatoid bodies. These features are consistent with E. histolytica, E. dispar, and E. hartmanni but size helps distinguish E. histolytica/E. dispar from E. hartmanni.
- a trophozoite of E. hartmanni that had a small, discrete, centrally located karysome, finely granular cytoplasm, and somewhat even peripheral nuclear chromatin. These features are also consistent with the three ameba listed above but, again, size is a distinguishing feature.
In this case, size was not given, but the size of the E. hartmanni could be extrapolated based on the size of the neighboring G. duodenalis cyst.
More on: Giardiasis: Nonpathogenic amoebae
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