Amoebiasis (Amebiasis): intestinal infection caused by Entamoeba

Clinical features and complications

Symptoms vary widely. Mild cases may cause loose stools or cramping, while more severe presentations include abdominal pain, mucus or blood in the stool, and tenesmus. Advanced intestinal disease can present as severe colitis with areas of tissue death (ulceration) that may lead to perforation and peritonitis. The parasite can also spread through the bloodstream to produce an amebic liver abscess, which causes fever, right upper-quadrant pain and systemic symptoms. Chronic blood loss from invasive lesions may result in anaemia. Many infections, however, remain asymptomatic and serve as reservoirs for transmission.

Life cycle, diagnosis and important distinctions

The parasite alternates between an infective cyst and an active trophozoite in the gut. Diagnosis is commonly by stool microscopy, antigen tests or molecular assays; imaging and serology are used when a liver abscess is suspected. It is important to distinguish Entamoeba histolytica from nonpathogenic relatives (for example E. dispar), which may appear similar on routine microscopy but do not usually invade tissues. Because laboratory methods differ in sensitivity, clinical correlation is essential.

Treatment and prevention

Therapy usually requires two complementary approaches: a drug that eliminates organisms living in the intestinal wall or organs (tissue-active agent) and a separate luminal agent that clears cysts from the intestinal lumen. Commonly used tissue-active drugs include nitroimidazoles, while luminal amoebicides such as paromomycin or iodoquinol are given to eradicate carriage. Preventive measures focus on improving sanitation, safe drinking water, hand hygiene and careful food handling. Travelers to endemic areas are advised to avoid untreated water and high-risk foods to reduce the chance of acquiring infection.

• High-risk regions include parts of Latin America (for example Central America and western South America), South Asia, and western and southern Africa, where transmission is linked to limited sanitation.
• Because many cases are asymptomatic, public-health control emphasizes hygiene, water treatment and detection of carriers.

History and public-health importance

Amoebic infections have been recognized for centuries; the relationship between a microscopic parasite and invasive intestinal disease was defined after the development of reliable microscopic and later immunological and molecular tests. Today amoebiasis remains a significant public-health issue in areas with inadequate sanitation and is an important differential diagnosis for persistent or bloody diarrhoea in returned travelers. Distinguishing amoebiasis from bacterial or viral causes of traveller's diarrhoea guides appropriate antimicrobial use and public-health responses.

For clinical guidance, laboratory testing and prevention strategies consult local public-health resources or specialist infectious-disease references. Further reading and resources are available from diagnostic and health agencies: see materials on intestinal infection and parasitology, and overview pages for clinical presentation and management (parasite biology, E. histolytica, waterborne transmission, colonic carriage, abdominal pain, bloody diarrhoea, colitis, ulceration, peritonitis, cyst forms, sanitation, Central America, western South America, South Asia, western and southern Africa, and liver involvement).