Amoebiasis

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2021年4月27日 (火) 10:06時点におけるVaccipedia.admin (トーク | 投稿記録)による版
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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
    • liver abscess
  • 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
    • most common in 20-40 y/o
  • >50% of patients have no previous dysentery

morphology

  • trophozoite 20-50 μm
  • cyst has 4 nuclei, each nucleus has a nucleolus

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

  • 6 nuclei in cyst