Entamoeba histolytica

Entamoeba histolytica

Updated: 01/26/2024

© Jun Wang, MD, PhD

 

General features

• A protozoan transmitted by ingestion of amebic cysts
•  Fecal-oral transmission usually through food or water
• Most cases asymptomatic, while up to 100k death annually

 Life cycle

Key clinical features

• Intestinal amebiasis and extraintestinal manifestations
• Bloody diarrhea due to colonic tissue damage
  
• Presentation depends on locations of infection
• Gastrointestinal: Gradual onset, fever, abdominal pain, tenesmus, diarrhea (with or without blood), dysentery
  
• Liver: Abscess, most common extraintestinal complication; fever, right upper quadrant pain, hepatomegaly with hepatic tenderness; may rupture and involve surrounding structures
• Respiratory tract: Rare, atelectasis and pleural effusions
• Brain: Abscesses, very rare, sudden onset symptoms such as headache, vomiting, and mental status changes with rapid progression to death

Colonoscopic findings

• Sharply defined ulcer

Pathologic findings

• Ulcer and trophozoites in necrotic tissue
• “Flask-shaped” ulcer
• Trophozoites in tissue

Diagnosis

• Stool microscopy: poor sensitivity, cyst or trophozoites
• Stool antigen detection
• Serology: high sensitivity and specificity, not helpful in distinguishing between an acute or previous infection
• Stool molecular studies: high sensitivity and specificity, more expensive

Treatment

• First-line treatment: Metronidazole

 

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