Entamoeba histolytica
Trophozoites
The trophozoites (trophs) of E. histolytica rang in size from 8 to 65 microns,with an average size of 12 to 25 ?m. The trophophozoite exhibits rapid, unidirectional, progressive movement, achieved with the help of finger like hyaline pseudopods. The single nucleus typically contains a small and central Karyosome. Variants of the karyosome include eccentric or fragmented karyosomal material. The peripheral chromatin is typically fine and evenly distributed around the nucleus in a perfect circle. The E. histolytica trophozoite finely granular cytoplasms, Red blood cells in the cytoplasm are considered diagnostic because E. histolytica is the only intestinal ameba to exhibit this characteristic. Bacteria, yeast, and other debris may also reside in the cytoplasm, but their presence, however, is not diagnostic
Cyst
The spherical to round cysts of E. histolytica are typically smaller than the trophs, measuring 8 to 22 ?m, with an average range of 12 to 18 ?m .The presence of a hyaline cyst wall helps in the recognition of this morphologic form. Young cysts characteristically contain unorganized chromatin material that transforms into squared or round – ended chromatoid bars in order cysts. The chromatoid bars may or may not be present in mature cysts. A diffuse glycogen mass is also usually visible in young cysts. As the cyst matures, the glycogen mass usually disappears. One to four nuclei are usually present. The mature infective cyst is quadrinucleated (containing four nuclei). The cytoplasm remains fine and granular. Red blood cells, bacteria, yeast, and other debris are not found in the cyst stage.
Life cycle
Once the infective stage is ingested, excystation occurs in the small intestine. As a result of the nuclear division, a single cyst produces eight motile trophozoites. These motile amebae settle in the lumen of the large intestine, where they replicate by binary fission and feed on living host cells. On occasion, trophzoites migrate to other organs in the body, such as the liver, and may cause abscess formation. Encystation occurs in the intestinal lumen, and cyst formation is complete when four nuclei are present. These infective cysts are passed out into the environment in human feces and are resistant to a variety of physical conditions. Survival in a feces contaminated environment for up to a month is common.
Clinical symptoms
Amebiasis, an infection of the intestine or liver by an ameba,often Entamoeba histolytica. The amebae are present in food or water that has had contact with infected feces. Mild amebiasis may not have symptoms. Severe infection may cause diarrhea, belly pain, jaundice, loss of appetite, and weight loss. It is dangerous in infants, the aged, and disabled patients. Amebic dysentery, intestinal amebiasis. An inflammation of the intestine caused by Entamoeba histolytica. Symptoms are frequent, loose stools flecked with blood and mucus. An amebic abscess often accompanies amebic dysentery.
Laboratory diagnosis
Stool examination is the method of choice for recovery of E. histolytica trophozoites and cysts. Through using wet preparations and permanent staining techniques on a suspected stool. When E. histolytica is suspected but not recovered in stool samples. Other laboratory tests including serological procedures may be utilized such methods currently available include Enzyme –Linked Immunosorbent Assay (ELISA).