Entamoeba histolytica

Entamoeba histolytica is a motile protozoan that infects approximately 10% of the world’s population, predominantly in tropical and subtropical regions. In the United States, this infection is most often seen in immigrants, overseas travelers, male homosexuals, and institutionalized persons. Infection is usually acquired through contaminated water or food and can be spread by the fecal–oral route. Sexual transmission has been reported occasionally. Risk factors for symptomatic infection include pediatric age group, malnutrition, pregnancy, immunosuppression, and steroids.