amebiaasi

Amebiasis, or amebiasis, is an infection caused by Entamoeba histolytica, a protozoan parasite in the Entamoeba histolytica complex. The disease can range from asymptomatic intestinal carriage to invasive intestinal disease and extraintestinal manifestations. The pathogenic E. histolytica contrasts with morphologically similar but nonpathogenic species such as E. dispar. Transmission occurs via ingestion of cysts in contaminated food or water, and is more common in settings with poor sanitation. Many infected people are asymptomatic carriers, while symptomatic disease is more frequent in tropical regions and among travelers.

In intestinal amebiasis, patients may experience abdominal pain, diarrhea that can be bloody with mucus, and tenesmus. Amebic dysentery may present with fever and weight loss. Invasion of the colonic mucosa can produce flask-shaped ulcers. Extraintestinal disease occurs when trophozoites reach the liver through the portal circulation, causing an amebic liver abscess; other organs such as the lungs or brain can be involved in rare cases.

Diagnosis relies on detecting trophozoites or cysts in stool, but these organisms can be indistinguishable from nonpathogenic relatives, so antigen-detection assays, serology, and molecular tests are increasingly used. Imaging (ultrasound or CT) helps identify liver abscesses. Colonoscopy may be employed in some cases but is not routinely required.

Treatment typically involves a tissue-active antimicrobial (a nitroimidazole) to treat invasive disease, followed by a luminal agent to eradicate intestinal carriage. Large liver abscesses may require drainage. Prevention focuses on sanitation, safe drinking water, and good hand and food hygiene, alongside precautions for travelers in endemic areas.