Amebiasis: Causes, Risk Factors, Symptoms, Treatment


Amebiasis also known as amoebic dysentery, it is a common parasitic enteral infection which causes diarrhea associated with blood and mucus. Amebiasis is caused by a protozoan called Entamoeba histolytica. Majority of the cases occur in the developing countries due to overpopulation and poor socioeconomic conditions and also due to negligence of personnel hygiene and poor sanitation. Amebiasis is acquired through the fecal-oral route. Amebiasis is contagious and an individual will be infected when they come into contact with an infected stool containing cyst of E. histolytica either by eating or drinking contaminated food and water.

If you present with persistent diarrhea, abdominal pain, and have a history of travel to or reside in areas with poor sanitation, seek prompt consultation with a Gastroenterologist or an Infectious Disease specialist in the Internal Medicine department to investigate the potential of Amebiasis.


There are three species of intestinal amoebas Entamoeba histolytica, Entamoeba despair and Entamoeba moshkovskii. Amebiasis is caused by a protozoan called Entamoeba histolytica which is the commonest and causes symptomatic disease. E. dispar is non-pathogenic i.e. it does not cause any harm or disease. These micro-organisms are indistinguishable from each other under a microscope, as they are morphologically similar and genetically different.

Risk Factors

Ø It is predominantly seen in developing countries due to poor socioeconomic conditions, poor environmental sanitation and lack of personal hygiene practices. Ø Bad water quality or untreated river water i.e. the transmission of the parasites occurs when a pond or river or a pool of water is contaminated with excrete of human or animals and the same water is being used for agriculture, and or personel hygiene Ø Younger individuals have more severe form of disease as when compared to older individuals. Ø Homosexual relations can augment the possibility of acquiring E. histolytica infections. Transmission: Ø Amebiasis is acquired through the fecal-oral route, i.e. when a host (human) ingests the food and water contaminated by the cyst form of E. histolytica Ø Transmission occurs only when a person comes into direct contact with the infected individual and consumes the food and water contaminated by the cyst form of E. histolytica Ø Contamination of water occurs mainly in the rainy season as the rain water flows down to the surface of ground through various streams and the contaminated water finally reaches and mixes the river water Ø Common house-hold pests like cockroaches and flies also spreads the cyst form of E. histolytica


Ø Most of the time the patients remain asymptomatic or have suffered from diarrhoea for a few days. The incubation period is between 2 - 4 weeks. Ø E. histolytica exists in 2 stages trophozoites and cysts. The cyst form protects them from the harsh stomach acids, which is responsible for the transmission of the disease. This single cyst upon reaching the small intestines ex-cysts and forms eight trophozoites as the small intestines provides a suitable habitat to the trophozoites. These trophozoites which ingest the blood are responsible for tissue invasion and causes damage of the tissues. When these trophozoites will get colonized in the colon, they infect the intestines and colon and causes severe diarrhoea with blood and mucus (dysentery). Humans and primates are the natural hosts for E. histolytica. Ø Symptoms range from mild abdominal cramps to watery diarrhoea and severe colitis with diarrhoea containing blood and mucus. Ø E. Histolytica mainly effects the gastrointestinal tract. But it also causes extra-intestinal amebiasis wherein it effects the liver (Amebic liver abscess ALA), which is the most common form of extra-intestinal amebiasis and rarely spreads to other organs like brain. Ø Amebic liver abscess generally presents with fever, pain and tenderness in the right upper quadrant region and hepatomegaly. Ø Lung amebiasis causes fever and right upper quadrant pain, cough with blood Ø Brain amebiasis is caused when amoeba travels up from the nose to the brain and causes destruction of tissues in the brain which leads to increased intracranial pressure, headache, vomiting, seizures, altered sensorium and meningitis.

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Different types of amebiasis would require different approach to diagnostic methods. Ø Blood tests like complete blood picture which could reveal high WBC counts and increased eosinophils, liver function test as liver enzymes could be elevated and C-reactive protein could be high due to inflammation. Ø Stool culture and sensitivity might be helpful sometimes, but they are time consuming and the sensitivity of diagnosis is about 50% only. Ø Colonoscopic biopsy would be helpful in detecting the minute ulcers in the colonic lesions. Ø Bio-fire gastrointestinal panel would be rapid and more accurate compared to the microscopic examination and would be helpful in faster diagnosis. Ø Extra-intestinal amebiasis like amebic liver abscess(ALA) would require radiology imaging to detect the presence of abscess in the liver. If the liver abscess is present then, would proceed with further steps like USG guided aspiration of the abscess and test the pus for culture sensitivity and PCR detection as these provide more sensitivity and specificity in diagnosing amebiasis.


The treatment with medications and duration of treatment vary depending upon the site of the amebiasis i.e. tissue infection or luminal infection and the age of the individual. Amebicides (medications used to treat amebiasis) are divided into 2 sub-groups: first-line agents like ornidazole, metronidazole, secnidazole, tinidazole; and second line agents like emetine hydrochloride, dehydroemetine and chloroqinue phosphate. Metronidazole is commonly used for the treatment of major and minor cases of amebiasis when exposed to E. histolytica. Diloxanide is used in children who are asymptomatic. In case of luminal infection, iodoquinoline or Diloxanide furoate is used. Asymptomatic carriers should also be treated in order to reduce and stop the spread of infection which also stops the risk of developing symptomatic infection. Generally, in the treatment of amebiais, metronidazole is often used in combination with second line agents. The drug metronidazole causes metallic taste which is a known side effect of the drug. The health care provider will be deciding on how-long the medication to be used. Based on the severity of abscess, a follow-up radiology imaging may also be advised.

Preventive Measures

Maintaining good hand hygiene practices like hand-washing with soap and water after using the toilet and proper disposal of soiled diapers and proper disposal of sewage is the most effective way in preventing amebiasis. Individuals with amebiasis should avoid sexual contact until the infection is treated and completely resolved. Drinking of boiled tap water or sealed bottle water would prevent the risk of acquiring amebiasis Always eat fresh fruits and vegetables that are peeled and boiled at high temperatures.

Do's & Don’t's

Do's Don't
Provide proper health education and community awareness on amebiasis.  Avoid drinking raw (unpasteurized) dairy products. 
Always drink boiled tap water or sealed bottled water. Abstain from dairy products when experiencing diarrhea.
Consume fresh fruits peeled by yourself and boiled vegetables.  Avoid consuming alcohol while on metronidazole.
Seek prompt and appropriate medical treatment for amebiasis to ensure effective resolution of the infection, and follow the healthcare provider's advice on when it is safe to resume sexual activity. Refrain from sexual contact until amebiasis is completely treated.

If you present with persistent diarrhea, abdominal pain, and have a history of travel to or reside in areas with poor sanitation, seek prompt consultation with a Gastroenterologist or an Infectious Disease specialist in the Internal Medicine department to investigate the potential of Amebiasis.

Frequently Asked Questions
Amebiasis is an infectious disease caused by the protozoan parasite called Entamoeba histolytica. It primarily affects the intestines but can also invade other organs, causing symptoms ranging from mild diarrhea to severe illness.
The parasite that causes amebiasis is usually transmitted through the ingestion of contaminated food or water containing the cyst form of Entamoeba histolytica. Poor sanitation and hygiene practices can contribute to its spread.
The symptoms of amebiasis can vary. Some people infected with the parasite may not show any symptoms, while others may experience mild to severe symptoms, including diarrhea (which may be bloody), stomach cramping, fatigue, weight loss, and fever. In severe cases, the infection can spread to other organs like the liver causing abscesses.
Diagnosis of amebiasis involves a combination of stool tests to detect the parasite or its DNA, along with imaging techniques like ultrasound or CT scans in severe cases where organ involvement is suspected.
The primary treatment for amebiasis usually involves medications to kill the parasite. Commonly prescribed drugs include metronidazole, tinidazole, or other medications specific to treating Entamoeba histolytica infections. In severe cases or complications like liver abscesses, drainage or additional medications may be necessary.
Preventive measures include practicing good hygiene, such as washing hands thoroughly with soap and water before handling food, using clean water sources, and maintaining proper sanitation. Avoiding consumption of contaminated food or water from uncertain sources, particularly in regions where the infection is more prevalent, can significantly reduce the risk of acquiring amebiasis.
Amebiasis itself is not considered highly contagious. However, the parasite can be transmitted through the ingestion of contaminated food or water containing Entamoeba histolytica cysts. Proper hygiene and sanitation practices help prevent its spread.
Yes, it's possible to become re-infected with Entamoeba histolytica after successful treatment. Reinfection can occur if a person is exposed to contaminated food, water, or surfaces carrying the parasite. Proper hygiene and sanitation practices are crucial to prevent reinfection.
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