Lecture on amebiasis

2021-03-23 12:00 AM

The small active form that lives in the lumen of the colon has a size ranging from 8 to 25 micrometres, moving more slowly than the large active form, in the cytoplasm, there is no erythrocyte.


Amoeba is a protozoan infection with Entamoeba histolytica, a disease that typically causes ulcers in the colon mucosa and is capable of causing abscesses in different organs (liver, brain ...). The disease tends to be long lasting and chronic if not actively treated. Approximately 90% of cases of amoebic infection are asymptomatic.

Research history

In 1875, FA Lesch discovered the first amoeba in the stool of a dysentery patient in Peterburg. He inflicted experimental amoebic dysentery on four dogs. On the 18th day of the disease, he opened the dog to check the colon and found a lot of ulcers and in these sores, there were many amoebae.

In 1883, R. Koch did research on the pathological anatomy of amoeba dysentery in Egypt. He found amoeba on slices across the ulcer of the colon, across the wall of the liver abscess in four corpses.

In 1891 Councilman and Lafleur named the disease and called "amoebic dysentery".

In 1903 Shaudin identified a single cell belonging to the family Entamoebidae and named it Entamoeba histolytica. They are of two forms: the pathogenic active form and the non-pathogenic active form.

In 1904 Kartulis found an amoeba in a brain abscess.

In 1912, the use of Emetin in the treatment of amoeba-induced diseases began.



Entamoeba histolytica protozoan belonging to Entamoebidae family, Amoebida order, Protozoa branch. The life cycle of the divided amoeba is 2 periods: the active and the holiday period (cocoon). However, it can change from the active form to the resting form or vice versa depending on the nutritional conditions of the environment in the host body. Based on the shape and physiology of E. histolytica, the amoeba is divided into 3 forms:

The large active form (Entamoeba histolytica forma magna) captured in feces, mucus-blood of patients with intestinal amoeba, size 15-30 micrometer, is most active at temperature 37 ° C and pH 6.5. The cytoplasm of amoeba has many red blood cells. E. histolytica forma magna, when entering the cell, usually shrinks in the cytoplasm to 4-8 micrometers in size.

Small active form (Entamoeba histolytica forma minuta) living in the lumen of the colon with size ranging from 8 to 25 micrometers, moving more slowly than the large active, in the cytoplasm without red blood cells.

The cocoon (Entamoeba histolytica forma cystica) is a small active form. The cocoon is oval in shape or round, 10-14 micrometers in diameter, covered by 2 sheaths. Young cocoons have 1 nucleus, but when old, there are 4 nuclei. Coccid formation is indispensable in the life cycle of the amoeba and plays a role in infection.


A patient (both acute and chronic) and a healthy person carrying a fecal discharge of amoeba cocoon, contaminating food and drinking water. Some animals like monkeys, dogs, cats, mice, etc. can get sick, but they do not expel the cocoons so they are not the source of the disease.


Through the gastrointestinal tract due to food and water contaminated with amoeba cocoons. Amoeba cysts exist in relatively good surroundings: at 17-20 ° C they persist monthly; at 45 ° C the cocoon dies after 30 minutes, at 85 ° C it dies after a few seconds. With Crezyl 1/250 disinfectant can kill amoeba cocoons within 5-15 minutes.

Sensory body - immune

 Amoeba can be infected by people of all ages, but 90% of infected people are asymptomatic, only 10% of infected people develop amoebic dysentery or abscesses in different organs.

People infected with E. histolytica will develop local immunity (in the intestinal wall) and the whole body, but there is no strong protection against pathogens.

Translation properties

The disease often spreads. However, in tropical countries with low social and economic life, the disease can cause large epidemics.

Mechanism of pathogenesis and pathology

Amoeba cocoons through food, water ... enter the human body through the digestive tract. When reaching the stomach, thanks to the effect of gastric juice breaking the shell, the four cores in the released cocoon develop into 4 small amoebas (forma minuta), then they move down to reside in the ileum, where rich in nutrients, pH is suitable and has many symbiotic bacteria. Normally, small amoeba does not penetrate the intestinal wall to cause disease but excreted by the colon down the stool. Some small amoebas shrink into cocoons and are also passed out in the feces, risking transmission to others.

When the intestinal wall is damaged (by other bacteria or trauma), the small amoeba can attack the intestinal wall, reproduce there, and secrete protein-digesting enzymes leading to cell necrosis of the intestinal lining. In the intestinal wall, at first, the amoeba causes congestion points in the mucosa, then forms small clumps on the surface of the mucosa, then gradually dies and forms ulcers. The ulcers can be up to 2-2.5cm wide, around the edge of the erection, edema, and congestion. The base of the ulcer is deep to the submucosa and covered with pus. Close together sores can connect to form larger, deep sores to the muscle layer and together with bacteria create deep abscesses, which can cause intestinal perforation and purulent peritonitis. Amoeba also creates granulomas in the intestinal wall that are sometimes difficult to distinguish from colon cancer.

When the ulcers damage the blood vessels of the intestinal wall, the amoeba can penetrate the bloodstream and travel through the body causing damage to organs other than the intestine such as the liver, lungs, brain, etc. Here amoebas can form abscesses.


Classification of clinical categories

According to the classification of the World Health Organization - 1972 divided into the following categories:

Intestinal amoeba

It is divided into:

Acute intestinal amoeba form.

Chronic entero-amoebic form: Chronic amoebic dysentery.

Complications in the intestine due to amoebas: Peritonitis due to perforation of the intestine, amoeba, appendicitis due to amoeba, colonic spasm due to scarring, rectal prolapse ...

Amoeba outside the intestine

It is divided into:

Amoebic Hepatitis: Hepatitis due to a non-purulent amoeba or liver abscess caused by amoeba.

Abscess due to amoeba in other organs (lungs, brain ...).

Skin amoeba.

Symptoms study according to each clinical form

Amoeba (amoebic dysentery)

Amoeba is the basic clinical form of the disease caused by E. histolytica. As the disease progresses amoeba can divide into the following:

Acute amoebic dysentery:


It lasts from 1-2 weeks to 3 months.


Can be gradual or acute. Some patients may see signs of progression: Fatigue, loss of appetite, dizziness, abdominal pain ... The main difference with bacillary dysentery is that patients with amoebic dysentery often feel relatively normal health, The patient usually has no fever or very mild fever, and the leukocytes do not increase.

Full play:

Amoeba dysentery is characteristic of the damaged colon also known as dysentery syndrome. Dysentery syndrome includes 3 main symptoms, mainly:

Cramping abdominal pain: Amoeba dysentery patients often have abdominal pain cramping in the right pelvic fossa (corresponding to the ileum area). In the case of prolonged disease, pain in both pelvic fossa areas (damage to the sigmoid colon and rectum) can be seen.

Pouring and "fake" going out: Patients often feel a burning sensation after each cramping pain, going out to be forced a lot and if prolonged can lead to complications of haemorrhoids or rectal mucosa. In patients with dysentery amoeba often see going out "fake" that is very pouring out but not having feces, different from the bacillus to draw out, often more or less there are feces.

Going out many times, bloody mucus stools: The number of times in patients with dysentery amoeba usually from 4-10 times/day, rarely go out as many times as bacillary dysentery. The stools are usually loose at first, with pulp, but in the next days, the stools are just clear like banana sap and blood. The mucus and blood are often separate from each other, as in bacillary dysentery.

In patients with amoebic dysentery in addition to intestinal manifestations, other organs are very little changed. Blood and urine tests were both within normal ranges.

Chronic amoebic dysentery:

Acute amoebic dysentery usually lasts 4-6 weeks, without specific treatment, it will turn to chronic almost as a rule. After the acute period, although untreated, the patient also feels better, the number of bowel movements decreases gradually as a tendency to cure. However, the disease is still progressing in chronic dullness and there will be acute relapses. Therefore, many authors divide chronic amoebic dysentery into 2 forms: Chronic having recurrent episodes alternating with normal and chronic times. Chronic amoebic dysentery can last up to 10 years or more.

Complications in the intestine due to dysentery amoeba:

Peritonitis due to perforation: A dangerous complication and difficult to diagnose because often occurs slowly and atypical. Peritonitis can be complete or localized in the right pelvic fossa, so it is easy to confuse appendicitis with perforation. The localized form may turn into chronic adhesion peritonitis or chronic periecalitis.

Colon ameboma (ameboma): A rare complication. Tumor location is usually in the cecum or colon up, more rarely can be seen in the colon corner of the liver and spleen. Tumors are sometimes large in size, causing colon narrowing or obstruction. However, when treated with specific amoebic destruction, the amoeba rapidly decreased and disappeared.

Colon polyps due to dysentery amoeba: As benign adenoma (adenoma) of different sizes and sizes, developing in the colon mucosa.

Intestinal bleeding due to amoebic dysentery: Intestinal bleeding is common in patients with acute amoebic dysentery or recurrent episodes of chronic amoebic dysentery. However, this complication is only seen in 0.5% of patients with dysentery amoeba only.

The rectal mucosa due to amoebic dysentery: This is also a rare complication and is seen in patients with chronic recurrent amoebic dysentery.

Amoebic appendicitis: A rare but serious complication and if not specifically treated, the death rate is very high.

Parenteral amoeba disease

Liver amoeba disease:

Amoeba can reach the liver and cause amoebic hepatitis or amoebic liver abscess.

Amoebic hepatitis:

Acute amoebic hepatitis often occurs with clinical manifestations of amoebic dysentery. The patient feels pain in the right lower rib region. The examination will reveal enlarged liver, mild or moderate fever, and rarely see jaundice. A blood test can show a moderate increase in leukocytes. Without specific treatment, amoebic hepatitis usually turns into an amoebic liver abscess.

Liver abscess caused by amoeba:

 Symptoms always present in patients with liver abscess caused by amoebas are liver enlargement and pain in the liver area. Ludlow sign (+) in the majority of patients. Pain increases with deep breathing or when lying on your right side. Patients often have high fever, may have non-periodic fever, fever with chills, sweating. The intoxication is evident: Fatigue, lethargy, emaciated face, pale skin.

In some patients with liver abscess due to amoeba appear jaundice, abdominal distension, shortness of breath.

Blood tests often have elevated leukocytes and a left-shift leukocyte formula. The rate of blood sedimentation increases, and liver enzymes increase. If the abscess is close to the upper surface of the liver, it will irritate the bronchi. X-ray shows reduced diaphragm mobility, possibly even pleural effusion. Ultrasound of the liver showed ultrasonic dilution. Amoeba liver abscess is usually few nipples, large lobe and mainly in the right liver lobe.

Lung amoeba disease:

Amoeba can reach the lungs through the bloodstream or liver abscesses close to the upper surface rupture causing diaphragm puncture, pus overflow causing pneumonia, pleura or amoebic abscess.

Pneumonia - pleura caused by amoeba:

Patients present with chest pain, dry cough or thick phlegm sometimes with blood. Low or no fever. Hear a small crackling in the lungs. Chest radiograph shows infiltrative clumps. Peripheral blood tests showed that leukocytes increased, in which eosinophils (E) increased, blood sedimentation speed increased. If the patient is not treated specifically, pneumonia - pleura will turn into a pulmonary abscess due to amoeba.

Lung abscess caused by amoeba:

The disease usually progresses chronically. Patients with mild fever with moderate or high fever, fluctuating fever. Cough with lots of chocolate-colored phlegm. Sputum smear can reveal E. histolytica. Chest radiograph will show lesions with transverse fluid levels.

amoebic lung abscess can lead to purulent pleuritis, purulent-gas overflow, liver-lung catheterization.

After and not amip:

Histolytica from the intestine enters the large circulation to the brain causing abscesses in the two hemispheres of the cerebrum. Patients with increased intracranial pressure syndrome: Severe headache, vomiting and nausea, toxic infection syndrome of different degrees. Neurological symptoms depend on the location of the damage in the brain.

An abscess caused by amoeba in some other organs:

Abscess of the spleen, kidney abscess, female genital abscess ... can be found but very rare.

Skin amoeba:

Skin amoeba is a secondary pathology. Skin lesions are usually found in the area around the anus, the perineal layer forming red patches, behind into ulcers. Amoeba can also create a fistula around the liver or near incisions of the liver, lung abscess.

Diagnosis of disease caused by the amoeba

Clinical basis (depending on the disease).

The colon is the primary residence of the amoeba so the intestinal amoeba is the basic disease experienced by most patients. Dysentery syndrome is the basic syndrome in amoebic disease with the following symptoms: Abdominal pain along with the colon frame, especially the cecum, colon up, pouring. After passing, the pain is lessened, the stool has clear mucus and separate blood, mucus, and blood. The number of times going out 4-10 times a day, once going out "fake". Not clear toxic infection syndrome. The patient may have a low fever, erratic fever during the day or no fever, symptoms of mild intoxication, which are not clear.

 Epidemiological bases: Contact with sick people, in the same kitchen, with sick people, living in epidemic-circulating areas, eating food suspected of being contaminated with the amoeba. Parenteral forms can be considered progressive bowel disease. In addition to the symptoms and syndromes of organs and organizations damaged by amoeba, it also has symptoms and syndromes of intestinal amoeba disease or a history of epidemiology related to the intestinal amoebic disease. Therefore, the exploitation of a history of amoebic dysentery is very important and very meaningful.

Test grounds: Determination of the diagnosis must be based on the determination of E. histolytica in the feces, pus of the patient's abscess. The most common method is to take fresh specimens on an optical microscope (must be examined immediately after taking specimens). In addition, it is possible to apply the immunofluorescence method, complement combination reaction, or amoebic culture in artificial media and transfer disease to experimental animals (cats, mice ...).

To identify the abscesses or amoebas can do an ultrasound of the liver, kidney, chest X-ray, brain, computed tomography (CT. Scanner).

In the case of an abscess of the liver, kidneys, lungs that can be poked, chocolate-colored pus will appear. Look for E. histolytica and Charcot-Leyden crystals in the stool or purulent fluid of the abscess.

Differential diagnosis

Depending on each disease, it is necessary to differentiate between different diseases.

For intestinal amoeba (dysentery amoeba)

Need to distinguish from bacillary dysentery because there is dysentery syndrome. However, bacillary dysentery usually evolves acutely with the toxic infectious syndrome. Symptoms of dysentery are also different: Abdominal pain along with the colon frame, especially the sigmoid colon and rectum, frequent bowel movements, mixed bloody mucus, or dilute like meat wash ... Distinguishing from chronic colitis, with Crohn's disease, ulcerative colitis, with dysbacteriosis, with heavy metal toxicity (lead, mercury ...), with hyperuricemia syndrome. Distinguishing from tumors of colorectal, tumors of the subframe ...

For hepatitis and liver abscess caused by amoeba: Hepatitis due to amoeba needs to be differentiated from viral hepatitis. The amoebic liver abscess should be differentiated from the bacterial abscess or biliary tract cancer, liver cancer ...

For pulmonary abscess: Need to make a differential diagnosis with pulmonary tuberculosis, lung tumor or lung abscess of other aetiologies.


Specific treatment - amoebic agents

Drugs act directly by exposure

Chiniofon (Mixiot, Yatren): Tablets 0.2-0.25g administered at a dose of 1.5g / day for 10 consecutive days. Can be combined with Chiniofon enemas to keep the colon (1-2g mixed with 200 ml of warm water).

Iodoquinol tablets 650mg / day for 10 days.

The drug acts on amoeba in cells (intestinal mucosa)

Emetin: Dose of 1 mg / kg heavy / day, intramuscularly for 5-7 days (0.04-0.06 grams / day; whole dose: 0.01 gram / kg heavy). In necessary cases, a repeat can be used, but must be 45 days away from the first one. 

Dehydroemetin (Mebadin): 2 times stronger than Emetin and less toxic. Dosage 1mg / kg body condition / 24 hours, intramuscularly for 5-7 days.

The drug works on both the amoeba and the cocoon

Metronidazole (Flagyl, Klion): Tablets 0.25g administered at a dose of 25-30mg / kg / day for 10 days.

Combination treatment

Pain relievers and intestinal mucosa: If the patient has severe abdominal pain due to colon spasm, use pain relievers and muscle relaxants such as Atropin, NOSPA, papaverine, spasmaverin etc. Do not use astringent drugs for intestinal mucosa such as bismuth salts; smecta ...

In the case of liver abscesses, lung abscesses with bacterial superinfection, amo-killing drugs must be combined with antibiotics (according to antibiotic), and at the same time, the abscesses must be solved with aspiration or surgery. liver vehicle due to the amoeba is too big (diameter> 6 - 8cm).


The main preventive measures are eating and drinking hygiene, avoiding the infection of amoeba cocoons in food, and drinking water. Handling fertilizers, absolutely do not use fresh fertilizers for vegetables and fruits. When using fresh fruits and vegetables, they must be washed, disinfected, or treated with ultraviolet rays to kill amoeba cocoons.

Treatment of amoeba carriers with metronidazole.