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.
Molecular methods using the polymerase chain reaction amplify E. histolytica genes from extracted faecal DNA. Sensitivity and specificity are high (80%–100% and 100%, respectively). The advantage of molecular detection is that it is extremely sensitive (able to detect < 1 parasite) and reliably able to differentiate non-pathogenic Entamoeba species from E. histolytica. Drawbacks of this method are the high level of expertise required and the cost. The availability of the test is limited, but at our institution it has proved extremely valuable.
Most patients have a gradual illness onset days or weeks after infection. Symptoms include cramps, watery or bloody diarrhea, and weight loss and may last several weeks. Occasionally, the parasite may spread to other organs (extraintestinal amebiasis), most commonly the liver. Amebic liver abscesses may be asymptomatic, but most patients present with fever and right upper quadrant abdominal pain, usually in the absence of diarrhea.