Entamoeba histolytica is a human intestinal parasite that causes amoebic dysentery (a diarrheal disease) and liver abscess. It is estimated that more than 500 million people are infected with E. histolytica worldwide. For example, in Bangladesh, 1 in every 30 children dies of diarrhea or dysentery before the age of 5. Since E. histolytica is a food- and water-borne pathogen with a high potential for mass dissemination, the NIH has classified it as a Category B priority bioterrorism agent. The disease can be contracted by ingestion of contaminated food or water that contains E. histolytica spores. Once in the human intestine, this parasite becomes highly motile and invades the wall of the intestine, causing tissue destruction and bloody diarrhea. The invasiveness of E. histolytica depends on its ability to engulf human red blood cells, bacteria, and other contents of human large intestines. The process of engulfing large particles, such as human cells, bacteria, or fungi is called phagocytosis. This scanning electron micrograph shows the process of phagocytosis of a fungus by E. histolytica. The micrograph was false colored in Adobe Photoshop. Multicolored thread-like filaments are called fungal hyphae. When fungi grow, they form these densely intertwined assemblages of thin filaments, dubbed mycelium. The surface of E. histolytica, enveloping around the fungus, is shown in pink.
The work was supported by a grant from the NIH (NIAID AI046414) to Dr. Lesly Temesvari.