Classification: Protist - group Sarcodina (ameboid protozoa)
Cell characteristics: Trophozoites - Amorphous; change shape constantly. Range in size from 12 to 60 micrometers. Small, central karyosome, beaded chromatin at nucleus' margin, finely granular cytoplasm; ingested red blood cells sometimes visible. Move by means of pseudopods (false feet).
Cysts - Non-motile. Characteristics as in trophozoites.
Source:
Pathogenicity: Causative agent of amoebic dysentery (amebiasis), a disease common in areas with poor sanitation. Trophozoites attach to the mucosa of the large intestine and cause tissue damage resulting in bloody diarrhea, ulceration of the large intestine in severe cases, abdominal pain, fever, fatigue and sometimes perforation of the bowel. Eats red blood cells.
Transmission: fecal-oral route, contaminated food or water.
Treatment: Chlorine is not effective, must use filtration.
Upon entering the less acidic small intestine, cysts undergo excystation. Mitosis produces eight small trophozoites from each cyst. Cysts develop when fecal material becomes too solid. Initially containing one nucleus, mitosis produces the mature cyst with four nuclei. Cysts are shed in the feces and may infect new hosts. They may also persist in the original host resulting in an asymptomatic carrier.
Entamoeba histolytica
