1. Amebiasis is common worldwide but most are asymptomatic.
It is NOT a common cause of traveler’s diarrhea and usually requires prolonged travel stay for luminal
disease as compared to liver abscesses which can occur with short exposure time.
3. Do not FNA liver abscesses if amebiasis is suspected; treat empirically and watch for improvement.
4. Liver abscesses require same treatment as for diarrheal disease but need paramomycin to clear luminal cysts.
! Organism is Entamoeba Histolytica
! 40-50 million people infected world-wide per year, especially in countries with poor sanitation and . 40,000
! In US prevalence is 4% with high risk groups being travelers, immigrants, institutionalized patients, gay
! NOT a common cause of traveler’s diarrhea. Unusual to acquire luminal disease if travelling <1 month to
Lifecycle of organism
Ingestion of cysts via contaminated water/food. One cyst can cause disease! Once in small intestine,
trophozoites hatch. Trophozoites then penetrate colonic mucosa to cause bloody diarrhea. Symptoms occur 1-3
weeks after exposure. In liver abscesses, organism ascends via portal venous system.
Over 90% are asymptomatic. Risk factors for disease include steroid use, HIV, alcohol use, malignancy,
pregnancy, malnutrition, very young.
! Diarrhea: 94-100%
! Bloody stool: >94%
! Abdominal pain
! Weight loss: 50%
! Colitis with perforation: 0.5%
Chronic disease: mimics inflammatory bowel disease! See weight loss, diarrhea, abdominal pain.
a) guaiac positive stool, NO fecal leukocytes
b) stool ova and parasite: see cysts or trophozoites. Send 3 specimens on separate days (85-95% sensitive)
a) antibodies present in 5-7 days (92-97% sensitive) and persist for years so positive result may be old
b) IHA (indirect hemagglutination): 90% sensitive
c) Antigen testings: