Intestinal Amebiasis (Entamoeba Histolytica Colitis,Amebic Dysentery,)

Intestinal Amebiasis
Body Parts: Abdomen
Medical Subjects: Digestive System

What Is The Intestinal Amebiasis

Entamoeba histolytica, mainly parasitic in colon, causes amebic dysentery or amebic colitis. Amoeba dysentery is also the most important pathogenic species in Rhizopoda. Under certain conditions, it can spread to liver, lung, brain, genitourinary system and other parts, forming ulcers and abscesses.


What Is The Cause Of Intestinal Amebiasis

The pathogenicity of amoeba is a complex process in which the worm interacts with the host and is influenced by many factors. The aggressiveness of Entamoeba histolytica is mainly manifested in the destruction of the solubility of the host tissue.

Tropical insect strains with high incidence of amoebic dysentery have strong virulence due to their long-term adaptation to tissue parasitism. However, in cold and temperate regions, the virulence of insect strains is weak, and there are more insect carriers. However, the virulence of insect strains is not fixed, which can be enhanced by animal passage or weakened after long-term in vitro culture. However, the virulence can be improved by animal inoculation. The appearance of virulence is related to the accompanying bacteria in intestinal cavity. Some people have done experiments by themselves, showing that simply swallowing the washed amoeba cysts of asthenia dysentery only leads to the state of carrying insects, and then swallowing the intestinal cells of patients leads to dysentery. This synergistic effect may be due to the fact that bacteria can provide physical and chemical conditions for the proliferation and activity of amoeba, such as appropriate redox potential and hydrogen ion concentration. At the same time, bacteria may also weaken the host's systemic or local resistance, and even directly damage the intestinal mucosa, providing an opportunity for amoeba to invade tissues.

The host's immune status also plays an important role in whether amoeba can invade tissues, and amoeba dysentery must break through the host's defense barrier before it can invade tissues for reproduction. Clinical and experimental data show that malnutrition, infection, intestinal dysfunction, mucosal damage and other factors cause the host's systemic or local immune function to be low, which is beneficial to the invasion of amoeba on tissues. In people with low nutrition standard or experimental animals, the incidence and pathological index of amoeba are significantly higher than those with balanced diet, and it is difficult to be controlled by drugs. Patients with intestinal or systemic infections such as typhoid fever, schistosomiasis and tuberculosis are prone to amoebic disease, which is not easy to cure after getting sick.

Entamoeba histolytica trophozoites invade the intestinal wall and cause amoebic disease. The common site is cecum, followed by rectum, sigmoid colon and appendix, while transverse colon and descending colon are rare, sometimes involving all or part of ileum of large intestine.


What Are The Symptoms Of Intestinal Amebiasis

In the diagnosis of amoebic disease, besides taking the patient's chief complaint, medical history and clinical manifestation as the diagnosis basis, the important thing is etiological diagnosis, and the only reliable diagnosis basis is the detection of amoebic pathogen in feces. Usually, the patients with large trophozoites are employed, while those with small trophozoites or cysts are only regarded as infected persons.

In diagnosis, intestinal amoebiasis should not be ignored, because amoebiasis lacks special clinical manifestations. The onset of the disease is slow, the poisoning symptoms are mild, and it is easy to recur. The severity of intestinal symptoms or dysentery-like diarrhea varies. Therefore, the cause of intestinal disorder or dysentery-like diarrhea is not clear, or it is suspected that it has no effect after treatment with sulfa drugs and antibiotics.

Clinical Picture

The incubation period of amoebic enteropathy varies from 1-2 weeks to more than several months. Although patients have been infected by Entamoeba histolytica cyst, they only live in symbiosis. When the host's resistance is weakened and intestinal infection, the symptoms begin to appear clinically. According to different clinical manifestations, it can be divided into the following types:

1. Asymptomatic Carriers: although patients are infected by Entamoeba histolytica, amoeba protozoa only exist as symbiotic, and more than 90% of them become cyst carriers without symptoms. Under proper conditions, it can invade tissues, cause lesions and appear symptoms. Therefore, from the point of view of controlling the source of infection and preventing disease, the carrier of cyst should be paid enough attention and must be treated.

2. Acute Atypical Amoebic Bowel Disease: It has a slow onset, no obvious systemic symptoms, unknown abdomen, only loose stools, sometimes diarrhea, several times a day, but lacks typical dysentery-like feces, which is similar to general enteritis, and trophozoites can be found in stool examination.

3. Acute Typical Amoebic Bowel Disease: The onset is often slow, with abdominal pain and diarrhea beginning, and the number of stools gradually increasing, reaching as many as 10-15 times a day, with varying degrees of abdominal pain, urgency and severity, which indicates that the disease has spread to the rectum. The stool is bloody and mucus, mostly dark red or purplish red, with fishy smell, and the worse case may be bloody stool, or the white mucus is covered with a little bright red blood. Patients' general symptoms are generally mild, their body temperature and white blood cell count may increase in the early stage, and trophozoites may be found in feces.

4. Acute Fulminant Amoebic Enteropathy: with rapid onset, poor nutritional status of the whole body, severe illness, obvious poisoning symptoms, high fever, chills, delirium, abdominal pain, and severe diarrhea, the stool is purulent, bloody, foul-smelling, or watery or watery stool, which can be more than 20 times a day, accompanied by vomiting, collapse, dehydration and electrolyte disturbance to varying degrees. Blood test showed neutrophil proliferation. It is easy to suffer from intestinal bleeding or perforation. If it is not treated in time, it may die from toxemia within 1-2 weeks.

5. Chronic Persistent Amoebic Enteropathy: It is usually a continuation of acute infection, with diarrhea and constipation appearing alternately. The course of disease lasts for months or even years, and it can be healthy as usual during intermission. Recurrence is often induced by improper diet, overeating, drinking, cold, fatigue, etc. Diarrhea occurs 3-5 times a day, stool is yellow paste, and trophozoites or cysts can be found. Patients are often accompanied by umbilical attack or dull pain in lower abdomen, anemia, emaciation, malnutrition and so on.


How To Check For Intestinal Amebiasis

Etiological Examination

1. Stool Examination

  • Live Trophozoite Test: The active trophozoites are often examined by direct smear with normal saline. Purulent bloody stools of patients with acute dysentery or loose stools of patients with amoebitis require clean containers, fresh stool samples, and the faster and better the inspection. In cold season, attention should be paid to heat preservation during transportation and inspection. During the inspection, take a clean glass slide, drop 1 drop of normal saline, dip a small amount of feces with bamboo sticks, smear it in normal saline, add a cover glass, and then put it under a microscope for inspection. The typical amoebic dysentery stool is sauce red mucus-like, with special fishy smell. Microscopically, there are more red blood cells and less white blood cells in mucus, and sometimes Charcot—Leyden crystals and active trophozoites can be seen. These characteristics can be distinguished from the feces of bacillary dysentery.
  • Cystic Inspection: Iodine smear method is commonly used in clinic, which is simple and easy. Take a clean glass slide, drop 1 drop of iodine solution, dip a small amount of fecal sample with bamboo stick, smear it in iodine solution and add cover glass, and then put it under a microscope for examination to identify the characteristics and number of nuclei.

2. Amoeba culture: There are many improved artificial media, such as Locke's solution, egg, serum medium, nutrient agar serum saline medium, agar peptone biphasic medium and so on. However, the technical operation is complicated and certain equipment is needed, and the positive rate of artificial culture of amoeba is not high in most subacute or chronic cases, so it seems unsuitable for routine examination of amoeba diagnosis.

3. Histological examination: Using sigmoidoscopy or fibrocolonoscopy to observe mucosal ulcer directly, and making biopsy or smear, the detection rate is the highest. It is reported that the cases with sigmoid colon and rectum lesions account for about 2/3 of patients with symptoms. Therefore, all suspicious patients should try to have colonoscopy, swab smear or biopsy. The trophozoites must be taken at the edge of ulcer, and it is advisable to see local bleeding after clamping. In addition to the attention characteristics, the examination of pus puncture fluid should be taken from the wall of pus cavity, which is easier to make trophozoites.


In recent years, many serological diagnostic methods have been reported one after another, among which indirect hemagglutination (IHA), indirect fluorescent antibody (IFAT) and enzyme-linked immunosorbent assay (ELISA) are more studied, but the sensitivity is different for different types of cases. IHA is highly sensitive, with the positive rate of 98% for intestinal amebiasis and 95% for extraintestinal amebiasis, but only 10%-40% for asymptomatic carriers. IFA is slightly less sensitive than IHA. EALSA is sensitive, specific and promising. Complement fixation test is also a trap for the diagnosis of ectoamoeba, and its positive rate can reach over 80%. Others, such as gelatin dispersin test and intradermal test, have auxiliary diagnostic value. In recent years, it has been reported that sensitive immunological techniques have been successfully used to detect amoeba specific antigen in feces and pus. Especially, the application of monoclonal antibody against amoeba murmur provides a reliable, sensitive and anti-interference tracer for immunological technology to detect pathogenic substances in host excreta.

Diagnostic Treatment

If there is a high degree of clinical suspicion, but the diagnosis can not be confirmed by the above examination, it can be treated with enough ipecacine injection or oral treatment such as anliping and metronidazole. If the effect is obvious, a preliminary diagnosis can also be made.


How To Prevent Intestinal Amebiasis

Amoeba enteropathy is prevalent all over the world, mostly in tropical and subtropical regions, but amoeba infection and prevalence also exist in colder regions and even in the Arctic Circle. Its infection rate is closely related to environmental sanitation, economic conditions and eating habits. It is estimated that about 10% of people in the world are infected, and the infection rate in some places can reach as high as 50%. In China, the distribution in rural areas is generally higher than that in cities. In recent years, due to the improvement of health conditions and living standards in China, acute amoebic dysentery and abscess cases are relatively rare except in some areas, and most of them are scattered chronic persistent or typical cases and carriers.

Infection Source: Chronic patients, convalescent patients and healthy carriers are the infection sources of this disease, with strong cyst resistance, which can survive for more than 12 days in wet and low temperature environment and 9-30 days in water. However, the capsule has weak resistance to dryness, high temperature and chemical drugs. For example, at 50℃, it will die in a short time, and the survival time in dry environment is only a few minutes. It cannot survive for a long time in 0.2% hydrochloric acid, 10%-20% salt water, soy sauce, vinegar and other condiments. 50% alcohol can kill it quickly.

Transmission Route: Entamoeba histolytica can be transmitted in the following ways:

  1. Encapsulation of polluted water sources can cause outbreaks in this area.
  2. When manure is used as fertilizer, unwashed and uncooked vegetables are also important transmission factors.
  3. Cysts spread by contaminating fingers, food or utensils.
  4. Both flies and cockroaches can come into contact with feces, and carry and vomit feces on the body surface, which will pollute food and become an important transmission medium.

Epidemic Characteristics: Entamoeba histolytica is widely distributed. In temperate regions, it can be prevalent from time to time, while in tropical and subtropical regions, its epidemic situation is particularly serious. Its incidence changes due to climate, with autumn as the most frequent occurrence, followed by summer. The incidence rate of male is more than that of female, and the incidence rate of adult is higher than that of children, which may be related to swallowing food containing cysts or age immunity.

To treat patients and those who carry cysts, drink water boiling, do not eat uncooked food, and prevent food contamination. Prevent flies from breeding and killing flies. Check and treat cystic and chronic patients in catering industry, and pay attention to personal hygiene such as washing hands before and after meals.


How To Treat Intestinal Amebiasis

General Treatment

In acute stage, you must stay in bed and give infusion if necessary. Give a liquid or semi-liquid diet according to the illness. Chronic patients should strengthen nutrition to strengthen their physique.

Pathogen Treatment

  1. Metronidazole: It has a strong killing effect on amoeba trophozoites and is safe. It is suitable for various types of intestinal and extraintestinal amoebic diseases, and is the first choice for anti-amoebic diseases at present. The dose is 400-800mg, which is taken orally three times a day for 5-10 days. Children are given 50mg per kilogram of body weight every day, divided into three times for 7 consecutive days. Occasional nausea, abdominal pain, dizziness, and palpitation during the medication period do not require special treatment. Do not use it within 3 months of pregnancy or nursing women. The curative effect reaches 100%.
  2. Tinidazole: It is a derivative of nitroimidazole compounds. The dosage is 2g per day. Children should take 50mg per kilogram of body weight every day, once in the morning, for 3-5 days. Occasional anorexia, abdominal discomfort, constipation, diarrhea, nausea, itching, etc. The curative effect is similar to or better than that of dropping.
  3. Emetine: Emetine has a high killing effect on trophozoites in tissues, but has no effect on Entamoeba in intestinal cavity. This medicine is very effective in controlling acute symptoms, but its radical cure rate is low, so it needs to be used in the same amount as quinoline halides. The dose is 1mg/kg per day, but not more than 60mg per day for adults, generally 30mg each time, twice a day, deep subcutaneous or intramuscular injection for 6 days.
  4. Note: The toxicity of emetine is great, so you should stay in bed during the treatment. Before each injection, you should measure blood pressure and pulse, and pay attention to the decrease of heart rhythm and blood pressure. Toxic reactions include vomiting, diarrhea, abdominal colic, weakness, myalgia, tachycardia, hypotension, precordial tenderness, abnormal electrocardiogram and occasional arrhythmia. Children, pregnant women, patients with cardiovascular and kidney diseases are prohibited. If you need to repeat treatment, at least every 6 weeks.
  5. Halogenated Quinolines: they mainly act on Entamoeba trophozoites in intestinal cavity rather than tissues. It is effective for mild and cystic patients, and is often used in combination with emetine or metronidazole for severe or chronic patients. 100-150ml iodoform solution was used as retention enema. The main side effects were diarrhea, occasional nausea, vomiting and abdominal discomfort. It is contraindicated for those who are allergic to iodine and have thyroid diseases.
  6. Others: Antamide, 0.5g orally, 3 times a day for 10 consecutive days. Paromomycin, 15-20mg/kg body weight per day, is taken orally for 5-7 days. Anliping, taken orally, 0.1g, 3 times a day for 10 days. All the above three drugs act on Entamoeba intestinal cavity.

Tip: In addition to metronidazole, the above drugs often need the combined application of two or more drugs to achieve better results.

Treatment of Complications

Under the active and effective treatment of metronidazole and ipecacine, all intestinal complications can be alleviated. Outbreak patients have mixed bacterial infection, so antibiotics should be added. Massive intestinal bleeding can be transfused. Those who need surgical treatment such as intestinal perforation and peritonitis should be treated with metronidazole and antibiotics.

If intestinal amoebiasis is treated in time, the prognosis is good. If complicated with intestinal bleeding, intestinal perforation, diffuse peritonitis and liver, lung and brain metastatic abscess, the prognosis is poor. After treatment, fecal examination of protozoa should last for about half a year, so as to find possible recurrence as soon as possible.


How To Identify Intestinal Amebiasis

Amoeba enteropathy needs to be differentiated from bacillary dysentery, schistosomiasis, intestinal tuberculosis, colon cancer and chronic nonspecific ulcerative colitis.

  1. Cellular Dysentery: acute onset, severe systemic poisoning symptoms, effective antibiotic treatment, microscopic examination of feces and bacterial culture are helpful for diagnosis.
  2. Schistosomiasis: It has a slow onset, a long course of disease, a history of contact with infected water, hepatosplenomegaly, and an increase in eosinophils in blood. Schistosoma eggs can be found in feces or hatched cercariae, and eggs can be found in intestinal mucosa biopsy.
  3. Intestinal Tuberculosis: Most of them have primary tuberculosis lesions, and patients have consumptive fever, night sweats and nutritional disorders; Feces are mostly yellow and gruel, with mucus and little purulent blood, and diarrhea and constipation appear alternately. X-ray examination of gastrointestinal tract is helpful for diagnosis.
  4. Colon Cancer: The patients are older, with frequent changes in defecation habits, thinning stools, progressive anemia and emaciation. Abdominal mass is palpable in the late stage, and X-ray barium enema and fibercolonoscopy are helpful for diagnosis.
  5. Chronic Nonspecific Ulcerative Colitis: It is difficult to distinguish clinical symptoms from chronic amoebic disease, but amoebic disease can not be found in stool examination, and this disease can be considered when anti-amoebic treatment still fails.

What Are The Complications Of Intestinal Amebiasis

Intestinal Complications

1. Intestinal Perforation: Acute intestinal perforation mostly occurs in patients with severe amoebic bowel disease, which is the most life-threatening complication of intestinal amoebic disease. Perforation can cause localized or diffuse peritonitis due to intestinal wall diseases, and perforation is more common in cecum, appendix and ascending colon. Chronic perforation first forms intestinal adhesion, and then often forms local abscess or penetrates into nearby organs to form internal fistula.

2. Intestinal Hemorrhage: The incidence rate is less than 1%, which can generally occur in patients with amoebic dysentery or granuloma, and is caused by ulcer invading intestinal blood vessels. Massive bleeding is caused by ulcer reaching submucosa, invading large blood vessels or destroying granuloma. Massive bleeding is rare, but once it happens, it is in critical condition and often leads to shock due to bleeding. A small amount of bleeding is mostly caused by bleeding from superficial ulcer.

3. Appendicitis: Because amoebic bowel disease is better than cecum, there are more chances to involve appendix. Appendicitis was found in 6.2%-40.9% of the autopsies of colon amoebic disease, and only 0.9% of them involved appendix. Its symptoms are similar to those of bacterial appendicitis, and it also has acute and chronic symptoms. However, if there is a history of amoebic dysentery and obvious right lower abdominal tenderness, this disease should be considered.

4. Amoeba Tumor: The intestinal wall produces a large amount of granulation tissue, forming a palpable lump. It usually occurs in the cecum, but also in the transverse colon, rectum and anus. It is often accompanied by pain, which is very similar to tumor and is difficult to distinguish from intestinal cancer. When the tumor is enlarged, it can cause intestinal obstruction.

5. Intestinal Stenosis: In chronic patients, the fibrous tissue of intestinal ulcer can be repaired to form scar stenosis, and abdominal colic, vomiting, abdominal distension and obstruction appear.

6. Perianal Amoebic Disease: This disease is rare and often misdiagnosed in clinic. When there is skin injury or anal fissure, anal inflammation and cryptitis, amoeba trophozoites can directly invade the skin and cause perianal amoebic disease. Sometimes the disease can be secondary to the treatment of hemorrhoids and fistula by thread-hanging. Amoeba trophozoites can infect the perianal tissues through blood, resulting in brown rash of millet size, which is flat and swollen with unclear edges, and finally forms ulcer or abscess. After rupture, pus and secretion are discharged. It is easy to be misdiagnosed as anorectal carcinoma, basal cell carcinoma or skin tuberculosis.

Extraintestinal Complications

Amoeba trophozoites can spread from intestinal tract to distant organs through blood flow and lymph, causing various extraintestinal complications, among which liver abscess is common, followed by lung, pleura, pericardium, brain, peritoneum, stomach, gallbladder, skin, urinary system and female reproductive system.

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