The Clinical and Economic Importance of Amoeba in Medicine and in the Human Health

Amoeba falls into the class Lobezea of the Protozoa phylum. The Lobezea are organisms which move with the help of pseudopodia. Reproduction is by binary fission. The production of a cyst is one of the stages in the life cycle. Among the pathogenic species for man is the Entamoeba histolytica. The causative agent of human intestinal amoebiasis, or amoebic dysentery.

Morphology

Enteroamoeba histolytica occurs in the human body in such forms:

1. Entamoeba histolytica forma magna is a vegetative large tissue form which feeds on the erythrocytes and does not become encysted:

2. Entamoeba histolytica forma minuta is a vegetative small commensal encysted form which lives in the lumen of the large intestine.

3. Cysts which develop from the forma minuta. E.histolytica penetrates into the tissues of the large intestine under the influence of a number of factors (lowered resistance of the human body due to various diseases, intoxications, overheating, overstrian, injuries, substances that cause lysis of cells and tissues. The parasite grows to a size of 30-50 micrometer in diameter and becomes capable of phagocytizing erythrocytes. This vegetative form is known as the tissue form. Entamoeba histolytica forma magna. It is usually found in the mucosanguineous stools (feces with blood and mucus) of patient with amebiasis. The amoeba ectoplasm is translucent, while the endoplasm is granular. The endoplasm contains the nucleus and food vacoules. The nucleus has a central karyosome. Forma minuta is the main form of E.histolitica. Its size ranges from 12 to 25 micrometer. Bacteria in phagocytes are found in small numbers in the endoplasm. Ectoplasm is poorly developed and accumulated in the pseudopodia, motility is decreased. Amoebas inhabit the upper part of the large intestine of a healthy man and known as luminal, cavity or commensal forms. The forma minuta transforms into a cyst. The cyst are spherical in shape with a diameter of 9 to 16 micrometer. They have thin-walled, double membranes, Fully mature cysts contain four nuclei. Immature cysts have one, two and sometimes three nuclei. Cysts are discharged with the feces for a long period of time and sometimes throughout life. They may re-enter the human body with foodstuffs or water and transform into luminal forms int he intestine.

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