Entamoeba histolytica is one of the most common parasitic infections worldwide, infecting about 50 million people and resulting in 40 000–100 000 deaths a year. In Australia, people at risk of infection include immigrants, travellers returning from countries of high endemicity, Indigenous people, and men who have sex with men. Clinical manifestations range from asymptomatic carriage to invasive disease. Amoebic colitis and amoebic liver abscess are the most common invasive manifestations observed in Australia. Diagnosis depends on a high index of suspicion and laboratory investigations.
Antibody testing to diagnose carriage of E. histolytica is unhelpful, as the sensitivity is only 8%. A positive antibody test confirms the suspicion of invasive amoebic disease provided the patient has not had a disease episode in the recent past, as antibody titres can remain high for years after successful therapy. For symptomatic intestinal infection and extraintestinal disease, treatment with metronidazole or tinidazole should be followed by treatment with iodoquinol or paromomycin.
In patients with invasive disease, metronidazole should be used in conjunction with a luminal agent to eradicate the organism. The role of surgery is generally limited to patients with complications of invasive disease. Surgical drainage is generally unnecessary in amoebic liver abscess, as cure can be achieved with medical therapy alone.