Amoebiasis

Amoebiasis is a parasitic infection caused by the protozoon Entamoeba histolytica. It serves as a significant cause of morbidity and mortality.

• It is the 3rd leading parasitic cause of death worldwide, surpassed only by malaria and schistosomiasis.
• Globally, amoebiasis affects approximately 10% of the world's population, with nearly 100,000 deaths yearly.
• It occurs in all age groups.
• Common in tropical areas with poor sanitary conditions and low socioeconomic status.

• First described by Lambi in 1859, as a one-celled parasite with no specific shape.
• Fedor Aleksandrovich Lošch established its pathogenic nature in 1875, in a patient with dysentery in St. Petersburg.

Simplest Organism of the Animal Kingdom

• Phylum: Protozoan
• Class: Rhizopoda
• Order: Amoebida
• Genus: Entamoeba
• Species: E. Histolytica

Forms

Trophozoite

• Colonizes the lumen of the large intestine
• May cause invasion of the mucosal lining

Cyst

• Person-to-person transmission
• Resistant to gastric acidity, digestive enzymes, harsh environmental conditions, and chlorine

Other Species of Entamoeba (Non-Pathogenic)

• E. dispar
• E. coli
• E. hartmanni
• E. gingivalis
• E. moshkovskii
• E. polecki

• Fecal contamination
• Other sources of fecal contamination
• Direct contact with dirty hands, objects, surfaces
• Sexual contact
• Geophagy (consumption of soil)
• Blood transfusion
• Mother to fetus transfer

• The ingestion of cysts of E histolytica:
• Excystation in the small bowel and invasion of the colon by the trophozoites.
• Incubation period varies from 2 days to 4 months.
• Invasive disease:
• Adherence of E histolytica to colonic mucins, epithelial cells, and leukocytes.
• Mediated by lectin.
• After adherence:
• Trophozoites invade the colonic epithelium.
• Produces the classical 'flask-shaped ulcers'.
• Spread of amoebiasis to the liver occurs via the portal vein:
• Liver abscesses form, filled with acellular proteinaceous debris (anchovy paste).
• Spread to other sites is via rupture of the liver abscess into contiguous structures and hematogenous route.

• Young children
• Malnutrition
• Alcoholism
• Prolonged use of steroids
• Prolonged use of antibiotics
• Immigrants/travelers to tropical areas
• Poverty
• Pregnant women
• Immunodeficiency
• Poor sanitary conditions
• Male homosexuals

Depends on the site of affectation:

• Non-Invasive Amoebiasis
• Asymptomatic
• Vague abdominal symptoms
• Self-limiting but may be recurrent.
• Invasive Intestinal Amoebiasis
• Fever
• Anorexia
• Nausea
• Abdominal pain
• Diarrhea
• Bloody and mucoid, little fecal material
• Tenesmus
• Fulminant Amoebic Colitis
• Severe bloody diarrhea
• Severe abdominal pain
• High fever
• Children younger than 2 years are at increased risk
• Intestinal perforation is common.
• Chronic Amoebic Colitis
• Recurrent episodes of bloody diarrhea and vague abdominal discomfort
• Amoeboma
• Presents as a right lower quadrant abdominal mass
• Appendicitis
• Toxic megacolon
• Weight loss and anemia
• Invasive Extra-Intestinal Amoebiasis
• Liver abscess
• Peritonitis
• Pleuropulmonary abscess
• Hepatobronchial fistula
• Pericarditis
• Cerebral amoebiasis
• Genitourinary involvement
• Cutaneous lesions

It’s a long list:

• Campylobacter
• Shigella
• Salmonella
• Yersinia
• Enteroinvasive Escherichia coli
• Enterohemorrhagic Escherichia coli

• Stool:
• Light microscopy:
• Not specific
• Cyst or trophozoites
• Enzyme immunoassay (EIA)
• Other stool tests:
• Occult blood is almost always present in invasive disease.
• Fecal leukocytes may be absent.
• Serum tests:
• Antibody tests:
• Most useful in patients with extra-intestinal disease
• Indirect hemagglutination antibody (IHA) test
• EIA
• Immunodiffusion (ID)
• Radiological Imaging:
• Chest radiography
• Ultrasonography
• CT
• MRI
• Other Ancillary Tests:
• FBC:
• Leukocytosis
• Eosinophilia is not a feature of amoebiasis.
• Mild anemia
• Erythrocyte sedimentation rate is elevated.
• Liver function tests:
• Elevated alkaline phosphatase
• Elevated transaminases
• Reduced albumin.
• Urinalysis may reveal proteinuria.

• Medical Care:
• Asymptomatic infections are not treated in endemic areas, except HIV-positive patients.
• Medications:
• Iodoquinol
• Paromomycin
• Diloxanide furoate
• Symptomatic intestinal disease and hepatic abscess:
• Metronidazole and tinidazole.
• Follow therapy with iodoquinol, paromomycin, or diloxanide furoate.
• Surgical Care:
• Drainage of abscess
• Tailored to the form of extra-intestinal disease.

• Hand washing
• Proper handling of food, water, and sewage
• Isolation of hospitalized patients (standard precaution)
• Treatment of drinking water
• Provision of portable water
• Avoid uncooked foods such as vegetables in endemic areas
• Avoid 'street' foods/snacks