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. A blood test is available but is recommended only if the patient's health-care provider thinks that the infection has invaded the wall of the intestines or some other organ, such as the liver. Blood tests might be positive if a person had an amebic infection in the past. Anyone can get amebiasis, but it is most common in people who live in developing countries with poor sanitary conditions. In the United States, the disease is seen most often in immigrants from developing countries, men who have sex with men, and people who live in group settings or institutions that have poor sanitary conditions.