Entamoeba histolytica - tumor necrosis factor: a fatal attraction.

Abstract

Entamoeba histolytica is a protozoan parasite, and is the causal agent of human amebiasis whose primary mode of transmission is the ingestion of food and/or water that is contaminated with feces containing E. histolytica cysts. Excystation is the stage in a parasite's life cycle, which occurs after the cystic form has been swallowed by the host. When excystation occurs in the intestinal lumen, trophozoites are released and colonize the large intestine, from where the parasite can travel along different life paths which determine the ultimate pathophysiology of amebiasis. E. histolytica trophozoites usually reside as a nonpathogenic commensal in the colon of most infected individuals, where they feed on the colon's microbiota [1]. In 90% of infected individuals, who are asymptomatic, these trophozoites divide and encyst, and the trophozoites and cysts are subsequently excreted in the feces. However, in the other 10% of infected individuals, symptomatic infection occurs because the trophozoites invade the colonic mucosa by burrowing. The burrows then coalesce to form flaskshaped ulcers and a resultant colitis (amebic dysentery). Disease progression may end with intestinal amebiasis or it may continue in a distal organ as an extraintestinal disease, usually the liver (amebic liver disease). However, rare extraintestinal manifestations of amebiasis with pulmonary, cardiac, and brain involvement can also occur [2].