The cysts can survive in the environment in water and food and on surfaces and objects. The parasite that causes amebiasis is found in the United States and around the world. People get amebiasis when they swallow Entamoeba histolytica cysts. In most persons, the parasite lives in the intestine and does not cause illness, or causes mild intestinal symptoms. Symptoms of the mild form of amebiasis include loose or watery stools, abdominal tenderness or discomfort, and stomach cramps.
Symptoms are stomach pain, bloody stools, and fever.
In rare cases, the parasite spreads outside the intestine to the liver and forms an abscess. Even less commonly, it spreads to other parts of the body, such as the lungs or brain. Symptoms usually start within 1 to 4 weeks, but the time between infection and symptoms can be shorter or longer. Infection is diagnosed by examining a stool sample under a microscope to look for the parasite. Because amebiasis can be difficult to diagnose, more than one stool sample might be needed.