September 15, 2010
September 15 - Entamoeba histolytica
Entamoeba histolytica is one of the most common parasites of humans and apes, with some estimates going as high as 50 million people infected worldwide. These single-celled amoebae are ingested as cysts that are shed in feces of other infected hosts. The protozoa excyst in the intestines and multiply there, usually resulting in symptoms ranging from mild diarrhea to full-on amebic dysentery. Eventually, they can bore through the intestinal wall and begin to infect other tissues such as the liver, spleen and brain. The amoebae will even gobble up red blood cells as seen in the photo (the dark circles in the outer two cells). Interestingly, it is now known that many suspected cases of E. histolytica that are based on microscopic examination are actually those of Entamoeba dispar, a benign species, which is actually up to 10 times more common that it's virulent cousin.