Parasitology Training Manual
Entamoeba histolytica
See images below.- Entamoeba histolytica is the only pathogenic intestinal amoeba of the Entamoeba species to infect humans.
- It is estimated that approximately 10% of the world population is infected with E. histolytica/dispar, but only a tenth of those
people are infected with E. histolytica.(9)
- Great strides are being made towards the the development of a vaccine against amebiasis.(19)
- E. histolytica is usually found in the cecum and terminal ileum.(6)
- It is the only invasive amoeba of the Entamoeba species infecting not only the intestine but causing secondary infections in
the liver and other tissues of the body.
- Laboratory diagnosis of E. histolytica/dispar is usually based on the finding of a trophozoite or cyst in the stool
concentrate or permanent stained smear. See the note on the Entamoeba Introduction Page regarding number of specimens for diagnosis.
- E. histolytica exists in the body as the fragile motile trophozoite and the hardy infective cyst.
- The cysts typically measures 10 - 20 microns with 4 nuclei and rounded or cigar shaped chromatoidal bars. An immature cyst
may have a vacuole and fewer nuclei. The only infective stage of E. histolytica is the mature cyst.
- The trophozoite of E. histolytica possesses one nuclei with a fine even peripheral chromatin. The punctate karyosome
is usually central but maybe off center. The cytoplasm usually contains little debris with a fine outer membrane. It usually
measures from between 12 and 20 microns.
Click on the image below to enlarge.
Return to Entamoeba Introduction
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Consulting
David M. Raymondo
MLT, CLS(m)
Professional Affiliation: Gamma-Dynacare Medical Laboratories, Ottawa, Ontario, Canada
Gamma-Dynacare is a Division of the Dynacare Health Group
