Amoebiasis is a parasitic infection of the intestines caused by the single-celled protozoan Entamoeba histolytica.

  1. histolyticausually enters the human body when a person ingests parasitic cysts in contaminated food or water. It can also enter the body through direct contact with fecal matter. The cysts are a relatively inactive form of the parasite that can live for several months in the soil or environment where they were deposited in feces. The microscopic cysts are present in soil, fertilizer, or water that’s been contaminated with infected feces. Food handlers may transmit the cysts while preparing or handling food. Transmission is also possible during anal sex or colonic irrigation.

When cysts enter the body, they lodge in the digestive tract. They then release an invasive form of the parasite called a trophozite. The parasites reproduce in the digestive tract and migrate to the large intestine. There, they can burrow into the intestinal wall or the colon. This causes bloody diarrhea, colitis, and tissue destruction. The infected person can then spread the disease by releasing new cysts into the environment through infected feces.

Once the trophozites have breached the intestinal walls, they can enter the bloodstream and travel to various internal organs. If they invade an internal organ, they can potentially cause abscesses, infections, severe illness and death.

When symptoms occur, they tend to appear one to four weeks after ingestion of the cysts. According to the Centers for Disease Control and Prevention (CDC), only about 10 to 20 percent of people who have amebiasis become ill from it. Symptoms at this stage tend to be mild and include loose stools and stomach cramping.

If the parasite invades the lining of your intestine, it can produce amebic dysentery. Amebic dysentery is a more dangerous form of the disease with frequent watery and bloody stools and severe stomach cramping. If the parasite enters your bloodstream, it can end up in your liver, heart, lungs, brain, or other organs, where it causes tissue destruction and abscesses. The liver is a frequent destination for the parasite. Symptoms of amebic liver disease include fever and tenderness in the upper-right part of your torso.


A doctor may suspect amebiasis after asking about your recent health and travel history. Your doctor may test you for the presence of E. histolytica. You may have to give stool samples over several days to screen for the presence of cysts. Your doctor may order lab tests to check liver function, which can help determine if the ameba has damaged your liver.

If damage to your internal organs is a concern, your doctor will probably order an ultrasound or CT scan to check for lesions on your liver. If lesions appear, your doctor may need to perform a needle aspiration to see if the liver has any abscesses. An abscess in the liver is a serious consequence of amebiasis.

Finally, a colonoscopy may be necessary to check for the presence of the parasite in your intestinal or colon tissue.



Treatment for uncomplicated cases of amebiasis generally consists of a 10-day course of metronidazole (Flagyl) given by mouth. Your doctor may also prescribe medication to control nausea if you need it.

If the parasite is present in your intestinal tissues, the treatment must address not only the organism but also any damage to your infected organs. Surgery may be necessary if the colon or peritoneal tissues have perforations.

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