Amoebiasis (amoebic dysentery)

Overview

Amoebiasis is an infection caused by Entamoeba histolytica, a single-celled parasite (a tiny living thing that lives on or in another body). It mainly lives in the large bowel (colon). The parasite is passed out in the stool of an infected person and spreads when someone swallows food or water that has been contaminated with that stool, or puts dirty fingers or objects in their mouth.

Most people who carry the parasite do not feel ill. Only about one or two in every ten infected people develop symptoms, and these are often mild, such as loose stools and stomach cramps. Symptoms usually begin a few weeks after the parasite is swallowed. In some people the parasite damages the wall of the bowel. This causes amoebic dysentery (diarrhoea with blood, stomach pain and fever) or long-lasting diarrhoea.

Rarely, the parasite travels in the blood to the liver and forms an abscess (a pocket of pus). Very rarely it reaches the lungs or brain. Amoebiasis is most common in hot countries where sanitation is poor and housing is crowded, including South Asia. Another harmless parasite, Entamoeba dispar, looks the same under a microscope, so the right tests matter. With the correct medicines, most people recover well.

Symptoms

• No symptoms at all, which is the case for most infected people
• Loose stools or diarrhoea that may last a long time
• Stomach pain and cramping
• Wind (gas), tiredness and weight loss without trying
• Pain in the back passage when passing stool, or a constant feeling of needing to go
• Bloody stools with fever and a tender stomach (amoebic dysentery)
• Vomiting in more severe illness
• With a liver abscess: fever and pain in the upper right side of the stomach, sometimes with yellow eyes or skin (jaundice)

Causes and risk factors

Causes

• Infection with the parasite Entamoeba histolytica, which lives in the large bowel
• Drinking water or eating food contaminated with stool that contains the parasite
• Eating raw vegetables or fruit contaminated with human waste, for example where human waste is used as fertiliser
• Swallowing the parasite from dirty hands or surfaces after contact with an infected person's stool
• Close contact involving the mouth and back passage, including some sexual contact

What makes it more likely

• Living in or travelling to hot areas with poor sanitation and crowded housing
• Drinking water that has not been boiled, filtered or treated
• Eating unwashed raw vegetables or unpeeled fruit
• Living in a rural area or having poor access to a toilet
• Living in an institution with poor hygiene
• Being very young or older, malnourished or pregnant, which raises the risk of severe illness
• Heavy alcohol use, cancer, or taking corticosteroid (steroid) medicines that weaken the immune system

Complications

Most people do not develop complications, but untreated or severe infection can cause problems. The parasite can damage the bowel wall and cause amoebic dysentery or long-term diarrhoea and weight loss. The most important complication is an amoebic liver abscess, which causes fever and pain under the right ribs and needs prompt treatment. Very rarely the parasite spreads to the lungs, brain or other organs. Without treatment the infection can come back. The medicines themselves can cause side effects such as nausea, so tell your doctor if you feel unwell during treatment.

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Diagnosis

Your doctor will ask about your symptoms, recent travel and the water and food you have had, and will examine your stomach. A large or tender liver can be a sign of a liver abscess. The main test is a stool test. Because the parasite is not always present, several stool samples collected on different days are often needed. Ordinary microscopy cannot tell Entamoeba histolytica apart from the harmless look-alike Entamoeba dispar, so some laboratories use special tests that can separate the two.

Blood tests may be done. An antibody blood test (serology) shows that a person has met the parasite, but it cannot always tell a current infection from an old one. An ultrasound scan of the stomach is used when a liver abscess is suspected, and fluid from an abscess can be tested. Sometimes a doctor looks inside the lower bowel with a thin camera (sigmoidoscopy). Stool is often tested again after treatment to check the infection has gone.

Treatment

1. See a doctor for stool tests, because the harmless look-alike Entamoeba dispar does not need treatment
2. If Entamoeba histolytica is found but you have no symptoms, the doctor usually prescribes one medicine that clears the parasite from inside the bowel (a luminal amoebicide)
3. If you have symptoms such as diarrhoea or dysentery, the doctor prescribes a nitroimidazole medicine (metronidazole or tinidazole) that kills the parasite in the body tissues
4. Straight after that, take a second, luminal medicine to clear any parasites left in the bowel, so the infection does not come back
5. A liver abscess is treated with the same two-step plan; a large abscess is sometimes drained with a needle guided by an ultrasound scan
6. If you are vomiting, hospital staff may give fluids and medicines through a drip into a vein until you can swallow tablets
7. Do not take anti-diarrhoea medicines unless a doctor advises it, and return for a repeat stool test if asked

Medicines in Pakistan

Medicines a doctor may use, by group. Read the role: some are only for special cases. Each link opens our page for that medicine, with every brand and its official DRAP price. Your doctor decides which medicine and dose are right for you.

Also used (not yet in our price list): Paromomycin (luminal amoebicide), Iodoquinol (luminal amoebicide)

Self-care and prevention

Self-care

• Take every medicine your doctor prescribes, including the second medicine after the first course, even if you feel better
• Go back for a repeat stool test if your doctor asks, to make sure the parasite has gone
• Wash your hands well with soap and water after using the toilet or changing nappies, and before preparing food or eating
• Do not take anti-diarrhoea medicines unless a doctor has advised them
• Drink only safe water: boiled tap water, filtered and treated water, or sealed bottled water
• Avoid raw vegetables, unpeeled fruit, drinks with ice and street food until you are well
• Tell your doctor if you feel sick or unwell from the medicines

Prevention

• Wash hands with soap and water after using the toilet or changing nappies, and before handling food or drinks
• Drink boiled water (boiled for at least one minute), properly filtered and treated water, or sealed bottled drinks
• Avoid ice, fountain drinks, unpasteurised milk products and street food where sanitation is poor
• Where sanitation is poor, avoid raw vegetables and choose fruit you peel yourself
• Use a proper toilet and keep human waste away from food crops and water supplies
• Get treatment if you are infected, because treatment and good hygiene make it much less likely that you pass it on

Common questions

Is amoebiasis contagious?

Yes. The parasite passes from the stool of an infected person to another person through contaminated water, food, hands or surfaces. The risk of passing it on is low once you are treated and keep good hand hygiene.

Why do I need two different medicines?

The first medicine (a nitroimidazole such as metronidazole or tinidazole) kills the parasite in the bowel wall and other tissues. A second luminal medicine is then taken to clear parasites that remain inside the bowel. Without the second step the infection can come back.

My stool report says amoeba but I feel fine. Do I need treatment?

Not always. A harmless parasite called Entamoeba dispar looks the same as Entamoeba histolytica under a microscope and does not need treatment. If special tests confirm Entamoeba histolytica, people without symptoms are usually given a luminal medicine. Ask your doctor what your report means.

Can I take anti-diarrhoea tablets for amoebic dysentery?

These medicines are generally avoided in amoebiasis because they can make the illness worse. Speak to a doctor or pharmacist instead, and see a doctor urgently if there is blood in your stool.

What is an amoebic liver abscess?

It is a pocket of pus in the liver caused by the parasite spreading from the bowel through the blood. It usually causes fever and pain in the upper right side of the stomach. It is diagnosed with an ultrasound scan and treated with medicines, and sometimes the pus is drained with a needle.

Sources

1. Centers for Disease Control and Prevention (CDC). Amebiasis | Amebiasis | CDC (2025).
2. Centers for Disease Control and Prevention (CDC) DPDx. Amebiasis [Entamoeba histolytica] (n.d.).
3. MedlinePlus (US National Library of Medicine). Amebiasis: MedlinePlus Medical Encyclopedia (2024).
4. Journal of the Pakistan Medical Association (Khan B, Afshan K, Firasat S, Qayyum M). Seroprevalence and associated risk factors of Entamoeba histolytica infection among gastroenteritis patients visiting the public healthcare system, Pakistan (2019).
5. Tropical Doctor (Alvi AR et al., Aga Khan University record). Amoebic liver abscess: Experience in a south Asian country (2010).

Prepared from the sources listed below by the MedInfoBase team. Last reviewed 16 October 2026. This page is general health information, not medical advice. It gives no doses and does not replace a doctor: talk to your doctor or pharmacist before starting, stopping or changing any medicine. How we write and check our pages.

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