Amoebiasis - Overview, Symptoms, causes

Edited By Irshad Anwar | Updated on Jun 11, 2025 09:30 PM IST

Entamoeba histolytica is a common protozoan parasite found in the large intestine of humans. It is acquired by faecal-oral transmission and can be sexually transmitted by oral-anal contact. Infection is commonly asymptomatic, but symptoms ranging from mild diarrhoea to severe dysentery may occur. The parasite is responsible for amoebiasis and liver abscesses. It is the third leading parasitic disease causing deaths in developing countries.

This Story also Contains

Life Cycle of Entamoeba Histolytica ( Amoebiasis)
Pathway of Amoebiasis in the Human Body
High-Risk Groups for Amoebiasis
Symptoms of Amoebiasis
Diagnosis of Amoebiasis
Prevention of Amoebiasis
Medications for Amoebiasis

Amoebiasis - Overview, Symptoms, causes

It is transmitted in areas where there is poor sanitation, which allows the contamination of drinking water and food with the stool of the people. It is most common in some of the Indian continents and also in parts of Central and South America. Amoebiasis is one of the important biology topics from the chapter Health and Diseases, CBSE class 12th.

Life Cycle of Entamoeba Histolytica ( Amoebiasis)

The life cycle of Entamoeba histolytica is described below, which will give you a better understanding of how it grows inside the human body.

The life cycle of Entamoeba histolytica is quite simple and consists of the infective cyst and invasive trophozoite stages.
Life cycle is completed in a single host, i.e., human
Humans get infected with cysts of E. histolytica from contaminated food and water. Infection can also be acquired directly by anogenital or oro-genital sexual contact.
The mature cyst is resistant to the low pH of the stomach, so it remains unaffected by the gastric juices.
The cyst wall is then lysed by intestinal trypsin, and when the cyst reaches the caecum or lower part of the ileum, excystation occurs. The neutral or alkaline environment, along with the bile component, causes excystation.
Excystation of a cyst produces 8 trophozoites. Trophozoites are active and carried to the large intestine by the peristalsis of the small intestine. Trophozoites mature and divide by binary fission.
The trophozoites attach to the mucus lining of the intestine by lectin and secrete proteolytic enzymes, which cause tissue destruction and necrosis. When the parasite gets access to blood, it migrates and causes extra-intestinal diseases.
When the load of trophozoites increases, some of the trophozoites stop multiplying and revert to cyst form by the process of encystation.
These cysts are released in faeces, completing the life cycle.

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Pathway of Amoebiasis in the Human Body

This disease is generally caused by a protozoan named Entamoeba histolytica.

Pathways	Explanation
Mode of entry	Ingestion of Cysts happens through contaminated water and food. Majorly, it is due to direct contact with faecal matter.
The inactive form of the cysts	The cysts are capable of surviving in the soil or any harsh environment for months. This is because this parasite is in an inactive form.
Parasite activation	Cysts once enter the digestive tract and release Trophozoites, the parasites are activated. Now, this active parasite usually reproduces inside the digestive tract and then migrates to the large intestine. Now these organisms burrow in the large intestine and cause the disease.
Transmission via food handlers	This is one of the most common ways of spreading the cysts of Entamoeba histolytica. The cysts spread while preparing food in unhygienic places.
Contaminated sources	The major sources of contamination are soil fertilisers and contaminated food with infected faeces.
Sexual transmission	A major possibility of transmission also happens when one is involved in activities like oral anal or anal sex with the infected person.

High-Risk Groups for Amoebiasis

Amoebiasis is caused by several reasons, some of the major ones discussed below. There are certain conditions which allow the parasite to grow and spread the Amoebiasis disease.

People who come from areas that have poor sanitary conditions.
People who are living in developing areas lack clean water and proper sanitation infrastructure.
Healthcare workers who are exposed to infected patients or contaminated environments.
Food handlers who are in contact with contaminated food, especially in underdeveloped areas.
People engaged in oral-anal sexual practices with the infected person.
People who have weak immune systems and are prone to other diseases also have a high risk of Amoebiasis.

Symptoms of Amoebiasis

Symptoms of Amoebiasis are often confused with different diseases. Some of the major symptoms and their explanations are given below:

Symptoms	Explanation Of The Symptoms
Asymptotic Infection	This is the most common symptom among the patients. No visible symptoms in the infected person.
Acute Amoebiasis	Diarrhoea or dysentery with blood in the stools. The stools are more frequent than normal.
Chronic Amoebiasis	The symptoms include signs like pus in the stools, weight loss, fever and fatigue.
Intestinal Symptoms	Symptoms are generally visible after 1 to 4 weeks of ingestion of Cysts. Loose stools, Stomach Cramps, Abdominal pain, and bloating are some of the common signs.
Fulminant Colitis	Inflammation in the colon leads to abdominal pain, bloody diarrhoea and in the worst cases, perforation of the intestines.
Peritonitis	Major inflammation is seen in the abdominal lining due to intestinal perforation. This also causes severe abdominal pain, fever and in some cases, there is a possibility of life-threatening infection.
Liver Abscess	Continuous fever and pain in the upper right quadrant of the abdomen. There is also a sensation of tenderness in the region. Occurs only if the parasite has infected the liver, which leads to abscess formation.
Cardiac and Cerebral Symptoms	In rare cases, the parasite affects the heart or brain, which leads to serious complications. Often treated by surgery.
Respiratory symptoms	The parasite enters the main bloodstream and damages the lungs and heart. This also leads to difficulty in breathing.
Other complications	Amoebic ulcers are common when we talk about infection in the intestine. When the parasite affects the main bloodstream, it also leads to anaemia due to the blood loss. Continuous diarrhoea will push the body to a dehydrated state.

Diagnosis of Amoebiasis

Infection of Amoebiasis can occur in several parts of the body. This is the only reason why several tests and diagnosis methods are used to get accurate treatment. Some of the major ones are described below:

Diagnosis Methods	Diagnosis Explanation
Stool test	A stool sample is tested for the presence of E. histolytica The presence of the parasite confirms Amoebiasis.
Enzyme-linked Immunosorbent Assay ( ELISA)	There is a detection of the antigen for antibodies present in the stool. This confirms the Amoebiasis.
Enzyme Immunoassay (EIA)	There is testing for extra-intestinal Amoebiasis. This is not a stool-based test.
Indirect Hemagglutination (IHA)	Antibodies are detected in patients' blood. If the antibodies are absent, the test is repeated after 7 to 10 days for confirmation.
Radiography and ultrasonography	X-rays and ultrasound are used to identify liver abscesses or other organ involvement in the Amoebiasis infection.
Computer tomography ( CT)	There is detailed imaging of scans provided in the test, which helps to detect intestinal perforation, liver abscess and extra-intestinal infection involved. This also includes the scan of the brain and lungs.
Magnetic Resonance Imaging ( MRI)	This test is useful for detecting cerebral Amoebiasis and also the severity of damage caused due to liver abscess.
Liver function test	This is conducted when the liver abscess is confirmed. Abnormal activities of the liver confirm the presence of the parasite.
Colonoscopy and Biopsy	There is direct visualisation of perforation in the colon and tissue. This is detected through biopsy, which is performed to identify the ulcers caused by Amoebiasis.
Chest X-Ray	A process is used in pulmonary complications which is suspected during other tests. This is a rare case of Amoebiasis and is spread throughout the lungs.

Prevention of Amoebiasis

There is no certain way through which you can completely avoid Amoebiasis. But there are certain measures which you can take to prevent Amoebiasis. Some of these are mentioned below:

Access to safe and clean drinking water.
Hands must be washed regularly with soap and water.
Avoid consuming food from unhygienic places.
Avoid eating foods which are unwashed and produced raw.
Use proper sanitation facilities.
Dispose of the sewage properly to prevent contamination.

Medications for Amoebiasis

Amoebiasis is normally treated with a combination of different medicines at the same time. It is generally advised to visit a doctor to eradicate the parasite from your intestine and also other infected tissues and organs. Some of the commonly used medications are mentioned below:

Metronidazole or Tinidazole: Generally used to kill the E. histolytica present in the intestine and other tissues.
Paromomycin: One of the luminal agents which is used to eradicate parasites from the intestine.
Diloxanide Furoate: Another luminal agent which is used for eliminating cyst carriers.
Dehydroemetine: Used in severe cases of extraintestinal Amoebiasis and especially in the case of liver Abscess.
Chloroquine: Used in combination with other drugs to treat Liver Abscess

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Frequently Asked Questions (FAQs)

1. What is another name for Amoebiasis?

Amoebic dysentery is the other name for amoebiasis.

2. What is the prevention for Amoebiasis?

The water should be cleaned not by chlorine treatment but by boiling. The food should be cooked with proper safety. Safe disposal of excreta should be done.

3. What are the three major symptoms of Amoebiasis?

The three major symptoms of Amoebiasis are diarrhoea ( bloody), abdominal pain and fatigue.

4. What is Luminal amoebiasis?

Luminal amoebiasis is defined as a disease in which no clinical symptoms and signs of a disease are apparent.

5. What is the main cause of the spread of amoebiasis?

Contaminated water is main cause of amoebic dysentery.

6. What is the treatment for Amoebiasis?

The most common treatment for Amoebiasis is medications which involve medicines like Metronidazole or Tinidazole, this is followed by luminal agents like Paromomycin that help in eliminating the cyst.