This is a histologic section of liver from a tortoise with amoebiasis. The large blue cells in the sinusoids are the amoebae. The condition is caused by Entamoeba invadens. Tortoises were initially thought to be carriers of the organisms, but they also can develop clinical (and usually fatal) disease. The infection starts in the intestine or colon, often in conjunction with bacterial infection or other parasites. From there, amoebae enter the blood stream and migrate to other viscera, especially liver and lung. Photo courtesy Northwest ZooPath.