Developed countries:

E. histolytica/E. dispar is 2.4% among immigrants

4% among travellers

27% among men who have sex with men

Most cases represent E. dispar colonization (only 4.6% of cases involved E. histolytica in some specific studies)

Developing countries:

Approximately 22%

For instance: Bangladesh 2.2% of preschool children have amoebic disentery.

Acute amoebiasis can present as diarrhoea or dysentery(*) with frequent, small and often bloody stools.

Chronic amoebiasis can present with gastrointestinal symptoms plus fatigue, weight loss and occasional fever.

Extraintestinal amoebiasis can occur if the parasite spreads to other organs, most commonly the liver where it causes amoebic liver abscess. Amoebic liver abscess presents with fever and right upper quadrant abdominal pain.

(*) Dysentery is defined as diarrhoea with visible blood in the stools. The most important and most frequent cause of acute dysentery is Shigella, especially S. flexneri and S. dysenteriae type 1. Other causes include Campylobacter jejuni, especially in infants, and, less frequently, Salmonella; dysentery caused by the latter agents is usually not severe. Enteroinvasive Escherichia coli are closely related to Shigella and may cause severe dysentery. However, infection with this agent is uncommon. Entamoeba histolytica cause dysentery in older children and adults, but rarely in children under 5 years of age.

Source:Stanley SL, Lancet 2003,361,1025-1034

4-20% of asymptomatic individuals infected with E. hystolytica develop disease within a year. The onset is often gradual with several weeks of symptoms.

Trophozoites use a galactose and N -acetyl-D-galactosamine (Gal/GalNAc)-specific lectin to adhere to colonic mucins and thereby colonize the large intestine. Cytolysis is undertaken by the amoebapores, a family of at least three small peptides capable of forming pores in lipid bilayers. E histolytica trophozoites can also kill mammalian cells by induction of programmed cell death (apoptosis).

Amoebic invasion through the mucosa and into the submucosal tissues is the hallmark of amoebic colitis.

Amoebic liver abscess is 10 times as common in men as in women and is a rare disease in children. It is the most common extraintestinal manisfestation of amoebiasis. Once treated the liver recovers to normality and does NOT leave scars!

Stool examination

Stool ELISA and PCR

Colonoscopy/flexible sigmoidoscopy

CT scan for suspected liver abscess