Diagnostic Parasitology

 Entamoeba histolytica

The cysts of Entamoeba histolytica, shown below, measure between 10 and 20 µm in diameter. The key identification feature is the number of nuclei; cyst will have 1 to 4 nuclei. In addition, the peripheral chromatin is generally evenly distributed.  In the images below, two nuclei are clearly visible. Image on the left is iron-hematoxylin stain (1000x), and the image on the right is an iodine wet mount (1000x).


The trophozoites of  E. histolytica typically have a diameter of  15 to 20  µm. They exhibit narrow pseudopods.  The image below left is an iron-hematoxylin stain (1000x). The image below right a wet mount of E. histolytica with a "finger-like" projection and ingested red blood cells (1000x).

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Copyright 2008 Don Lehman