Amebiasis

Introduction

Amebiasis is an infection caused by Entamoeba histolytica, an intestinal protozoan

-Entamoeba histolytica  is acquired by ingestion of viable cysts from fecally contaminated water, food, or hands 

-E. histolytica is infectious in the cyst form

Symptoms & Signs

Intestinal amebiasis: 

-The most common type of amebic infection is asymptomatic cyst passage

-After ingestion by humans, cysts enter the small intestine and form trophozoites, which adhere and invade the intestinal epithelium and form “flask-shaped” ulcers with a pinhead-sized center and raised edges 

-Fever, vomiting, abdominal distention, abdominal pain, tenderness, hepatomegaly, hypotension, diarrhea,dysentery, weight loss, and heme-positive stools 

Amebic liver abscess:

-The most common extraintestinal manifestation is amebic liver abscess

– Fever, right-upper-quadrant pain, intercostal tenderness, right-sided pleural effusion 

Diagnosis 

Diagnosis is by stool examinations for Entamoeba or its antigen or by serologic tests 

Fecal findings: a positive test for heme, a paucity of neutrophils, amebic cysts or trophozoites 

Liver abscesses: 

Needle aspiration: reddish “anchovy paste” purulent material 

Imaging: Ultrasonography, CT or MRI 

Treatment 

Intestinal amebiasis: 

-Treatment of amebiasis involves the use of tissue amebicides and luminal amebicides 

Tissue amebicides: they act on organisms in the bowel wall and the liver 

Metronidazole, tinidazole, chloroquine, emetines 

Luminal amebicides: they act on organisms only in the lumen of the bowel

Diloxanide, iodoquinol, paromomycin 

Diloxanide is commonly used as the sole agent for the treatment of asymptomatic amebiasis 

Liver abscess: 

Metronidazole is the drug of choice for amebic liver abscess; aspiration, percutaneous drainage, and surgery 

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