Entamoeba histolytica

Classification

Species of Amoebae, Table 1.

Life Cycle

Fig. 1.

Figure 1

Life cycle of Entamoeba histolytica. 1 Cysts with 4 nuclei (i.e., metacysts) are ingested orally with contaminated food or drinking water ( A–C). 2–4 After excysting in the small intestine, both the cytoplasm and nuclei divide to form 8 small amoebulae (i.e., metacystic trophozoites). 5, 6 Mature trophozoites (i.e., minuta forms) reproduce by constant binary fission. 7 Uninucleate cyst (i.e., precyst) contains chromatoid bodies and (often) a large glycogen vacuole. 8 Cysts with 2 nuclei and chromatoid bodies. 9 Cysts with 4 nuclei (metacysts) are set free with the feces and become infectious when ingested by man. 10–11 Some of the minuta forms may grow to magna forms, which enter the intestinal wall and, via the bloodstream, other organs such as liver, lung, and brain (11 a–c), where they lead to abscesses (i.e., Amoebomae). Living amoebas are only found at the periphery of these amoebomae. AB, abscess; CH,...