Entamoeba histolytica

Background

Microbiology

• Intestinal protozoan parasite within the genus Entamoeba
• Microscopically distinguishable from the non-pathogenic E. dispar, E. moshkovskii, and E. bangladeshii

Epidemiology

• Causes 34 to 50 million cases annually and up to 100,000 deaths

Clinical Presentation

Amoebic diarrhea and dysentery

• Amoebic diarrhea, with or without dysentery, is common
  • About 15 to 30% of cases involve amoebic dysentery (with macroscopic or microscopic blood)
• Typically a subacute onset over 3 to 4 weeks and abdominal pain
  • However, can be up to months
• Fever is rare, even in dysentery
• In children, can lead to intussusception, perforation, and necrotizing colitis

Amoebic liver abscess

• Amoebic liver abscess is far more common in men than women, and rare in children
• Symptoms progress over 2 to 4 weeks, with fever, cough, and abdominal pain
  • The pain is typically a dull ache in the right upper quadrant or epigastrium

Disseminated emoebiasis

• Metastatic infections are possible, most often from direct extension of a liver abscess
• Most commonly spreads to chest, with empyema, bronchohepatic fistula, pericarditis
• Cerebral disease is rare but can happen

Diagnosis

• Microscopically distinguishable from the non-pathogenic E. dispar, so needs molecular tests to confirm diagnosis