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Entamoeba histolytica
epidemiology
- worldwide
- 40-50 mil. symptomatic cases per year
- number of asymptomatic cases unknown
- 40,000-50,000 per year
- sexual transmission in developed countries
life cycle and pathophysiology
- feco-oral infection of cyst
- hutch in small intestine into trophozoite
- reside in large intestine
- propagate by binary fission
- some penetrate large intestine wall
- bloody diarrea
- trophozoites phagocityze RBC
- only RBC phagocitizing trophozoite means infection
- non-RBC-phagocitizing trophozoite means colonization
- some invade into portal vein through liver
- some encyst in large intestine
- cysts are excreted from anus
clinical manifestation
- incubation a few days to years
- 80% of infection are asymptomatic
- mild, extensive, extreme
- large intestine ulcer
- flask-shaped ulcer in histpathology
- advanced disease mimics ulcerative colitis and Crohn's disease
amoebic liver abscess (ALA)
- right lobe: left lobe =4:1
- male: female=10:1
- all age groups
- >50% of patients have no previous dysentery
morphology
- trophozoite 20-50 μm
- cyst has 4 nuclei, each nucleus has a nucleolus
treatment
- metronidazole for trophozoite
- paromomycin for cyst eradication
Entamoeba dispar
- formerly named as E. histolytica in 1903
- non-pathogenic type of old E. histolytica was distinguished as E. dispar in 1925
distribution
- E. disper vs E. histolytica
- 3:1 in developing countries
- 10:1 in developed countries
Entamoeba coli