What Is Amoebiasis?

Amoeba has two phases: trophozoite and cyst. After the trophozoites escape from the cysts, they parasitize the intestinal cavity or intestinal wall of the large intestine. The contents of the large intestine, including bacteria, are used as nutrients. The size of the trophozoite varies from 12 to 60um, and 15 to 30um is common.

Ji Aiping

(Chief physician)

Beijing Institute of Tropical Diseases, Beijing Friendship Hospital

Amoebic infections are caused by Rhizopoda, Amoebina, Entamoebidae, Entamoeba Caused, the clinical habit is referred to as amoeba. Among them, intestinal amoebas, although there are many species, are mostly parasitic in humans as co-living organisms without pathogenicity. Only amoeba in the lysed tissue can cause disease under certain conditions and is considered to be a disease. It is amoeba that is pathogenic.

Western Medicine Name: Amoebiasis
Other name: Amoebiasis, amebiasis
Affiliated Department: Internal Medicine-

The main symptoms: Abdominal pain, diarrhea
Main cause: Protozoal infection
Contagious: Contagious

Amoebiasis etiology

The trophozoite is very weak, dying within a few hours at room temperature, and dying within a few minutes when encountering dilute hydrochloric acid. The trophozoite can invade and destroy tissues under appropriate conditions, causing colonic lesions and causing clinical symptoms. Therefore, the trophozoite is an invasive form of amoeba within the lytic tissue, but it has no infection capacity. Because it dies quickly outside the body, it is quickly broken by stomach acid even when it enters the digestive tract. Encapsulation is very resistant to the outside world. It can survive in stool for more than 2 weeks and in water for 5 weeks. It can tolerate the effects of commonly used chemical disinfectants. However, it is more sensitive to heat and dryness, and it will die after heating to 50 ° C for several minutes. The cysts can be discharged to the outside world with feces. Ingestion of food or water contaminated by cysts causes infection. So the infection type of amoeba in lytic tissue is cyst. After the cyst is swallowed, it is not affected by gastric acid, and reaches the ileum through the stomach. Due to the action of the basic intestinal digestive juice of the small intestine and the activity of the worm body, the worm body containing the four cores escaped from the cyst wall. After a series of complex changes, the worm body split into four to eight small trophozoites, which settled in the cecum and proximal large intestine. ^[1]

Causes of amoebiasis

After the cyst is swallowed, it enters the lower part of the small intestine. The trophozoites escape from the capsule and fall with the feces. They live in the cecum, colon, and rectum and live together. They feed on bacteria and superficial epithelial cells in the intestinal cavity. Under suitable conditions, the trophozoite invades the intestinal mucosa and causes ulcers. When it reaches a certain range and degree, it causes dysentery.

Amoebiasis epidemiology

The disease is found all over the world, and the level of infection is highly related to environmental sanitation and nutritional status of residents in various places. Amoebiasis in histolytic tissue is more frequent in tropical, subtropical and temperate regions, most of which occur in autumn and second in summer. The incidence is higher in rural areas than in urban areas, with more men than women, more adults than children, and fewer young children, which may be related to the chance of swallowing encapsulated food.

1. Sources of infection: Chronic patients, patients in recovery period, and healthy "exhausting cysts" are the source of infection of the disease. Acute patients are not the source of infection when only trophozoites are excreted in their stool.

2. Ways of transmission: The cysts can survive in the soil for more than 8 days; in humid and cool environments, such as feces, they can survive for several weeks. Encapsulation can enter the body by contaminating drinking water, food, vegetables, etc. In places with poor sanitary environment, water or food is easily contaminated by feces. In areas where manure is used as fertilizer, unwashed and undercooked vegetables are an important transmission factor. Flies and cockroaches can contact feces, carry on the body surface, and vomit and defecate, which will contaminate food with cysts and become an important transmission medium.

3. Epidemic characteristics: Amoebiasis in lytic tissues is more common in tropical, subtropical, and temperate regions, with more cases occurring in autumn and less in summer. The incidence is higher in rural areas than in urban areas, with more men than women, more adults than children, and fewer young children, which may be related to the chance of swallowing encapsulated food.

Pathological changes of amoebiasis

Colonic lesions begin with a localized submucosal abscess, which is scattered and isolated. The tissue destruction gradually develops in depth, from the submucosa to the muscle layer, forming a typical flask-like ulcer with a small mouth and a large bottom. Early lesions can only be seen with small mucosal ulcers, which are slightly upturned around the surface, but the edges are irregular. Dark yellow or gray-black necrotic tissue can be seen on the surface of the ulcer, and trophozoites can be found in the deep part. The mucosa between the ulcer and the ulcer is generally normal, and without a secondary bacterial infection, there is no inflammatory response. Lesions are mainly of the nature of tissue necrosis and cell lysis, rather than inflammation.

The blood vessels at the bottom of the ulcer have thrombosis, but sometimes the lesions can damage the arterioles and cause severe or even life-threatening bleeding. Ulcers can also penetrate the muscle layer to the intestinal wall, making the latter extremely thin, and the contents of the intestine can leak into the abdominal cavity, or penetrate the intestinal wall, causing localized abscess or diffuse peritonitis.

In chronic disease, polyp-like debris can reach the intestinal lumen. Scars can still be seen after the ulcer heals. As the trophozoite repeatedly invades the mucosa and is infected with secondary bacteria, the intestinal mucosal tissues proliferate and hypertrophy, and massive granuloma can appear, becoming ameboma, which is more common in the anus, anorectal junction, transverse colon and cecum. Amoebic tumors are sometimes extremely large and hard to distinguish from colorectal cancers.

The distribution of amoeba lesions was in the order of cecum and ascending colon, anus, rectum, appendix, and lower ileum. The trophozoite can enter the portal vein blood flow, form an abscess in the liver, and can flow into the lungs, brain, spleen and other tissues and organs in the form of emboli to form an abscess.

The lesions were seen under the microscope, and the main changes were the tissue necrosis. Mild or moderate lymphocytic infiltration with a small amount of neutrophils, which is more pronounced when secondary infections occur. Amoeba trophozoites are covered throughout the lesion, especially on the margins where the lesion spreads, even in adjacent normal tissues.

Clinical manifestations of amoebiasis

Onset is usually slow, with abdominal discomfort, thin stools, sometimes diarrhea, several times a day, and sometimes constipation. Symptoms such as pus and blood dysentery in diarrhea. If the disease develops, dysentery-like disease can increase to 10 to 15 times or more per day, accompanied by acute stress, severe abdominal pain and bloating. The ileum, transverse colon, and especially the rectum can be tender, sometimes like ulcers or appendicitis. Systemic symptoms are generally mild and very different from bacterial dysentery. Fecal examination may have a small amount or a large amount of trophozoites, and the stool has a rotten smell.

The symptoms of amoebic liver abscess appear in the intestinal amoeba for several months, years, or even ten years, and some people have never suffered from intestinal amoebiasis. The onset is mostly gradual, with long-term irregular fever and nighttime night sweats as the main expendable symptoms. There may be a history of dysentery-like episodes one to several years before the onset of illness. The total number of white blood cells in the early stages of laboratory tests has increased significantly. Between 15,000 and 35,000, neutrophils can exceed 80%. If trophozoites or cysts can be found in the stool, it is helpful for diagnosis. Through diagnostic puncture, if a typical chocolate-like pus can be drawn and Xia Yilei crystals and tissue residues can be found in it, the diagnosis can be established. If amoeba trophozoites can be detected again, the diagnosis is more accurate.

Amoebiasis complications

There are two types of enteral and parenteral. Parenteral complications will be described in liver amoebiasis and other rare parenteral amoebiasis. The following refer to intestinal complications of amoebiasis.

1. Intestinal perforation: This is the most life-threatening complication of intestinal amoebiasis. Perforation can cause intestinal contents to penetrate the abdominal cavity due to intestinal wall lesions, resulting in localized or diffuse peritonitis or abdominal abscess, and occasionally caused by traumatic puncture during rectal endoscopy. Diffuse peritonitis is more common and has a poor prognosis. Deep intestinal wall ulcers mostly cause chronic perforation, and the sites are mostly in the cecum and appendix. Traumatic perforation is more common in the rectum.

2. Intestinal bleeding deep ulcers: can erode blood vessels, cause intestinal bleeding of various sizes, major bleeding is life-threatening, and must be actively rescued and given anti-amoeba medication.

3 Appendicitis: Amoeba can invade the appendix, and its clinical manifestations are similar to those of general appendicitis. It may even become the first symptom of intestinal amoebiasis and is prone to perforation.

4 Amoebic tumors: Amoebic ulcers penetrate deep into the myometrium. The lesions affect the entire intestinal cavity and produce a large amount of granulation tissue. The large masses that can be touched are mainly located in the cecum. They are also found in the transverse colon, rectum and anus. Not easy to distinguish from bowel cancer. Can cause intestinal obstruction.

5. Other amoebic dysentery can cause ulcerative colitis after repeated episodes. Intussusception sometimes occurs, and most of the seats are at the junction of the cecum and colon, with severe pain and palpability. Colonic stenosis can occur after chronic amoebic dysentery, but it is rare.

6. Amoebic disease of the liver: refers to the dissolution of amoeba in the tissue through the portal vein to the liver, causing the liver cells to dissolve and become necrotic and become an abscess. It is usually called amoebic liver abscess, which is the most common complication of intestinal amebia The main symptoms are long-term fever, increased autologous cells, systemic consumption, and liver enlargement and tenderness, which are prone to cause chest complications. About half of the patients with amoebic liver abscess have a history of amoebic dysentery from one week to several years ago.

Amoebiasis disease diagnosis

Amoebiasis diagnostic criteria

The diagnostic principles recommended by the WHO experts are:

1. Detection of trophozoites with erythrocytes from fresh stool samples or trophozoites from intestinal wall biopsies is a reliable basis for the diagnosis of this disease.

2. Only 1-4 nuclear cysts or intestinal trophozoites were found in stool samples, which should be reported as amoeba and dispare amoeba infections. At this time, even if the patient has symptoms, the diagnosis of intestinal amebiasis cannot be obtained based on this. It should be confirmed according to the epidemiological history, serum antibody test, fecal antigen test or PCR test that the infected strain is indeed amoeba Only then can the diagnosis be established. Otherwise, you must look for other causes of diarrhea.

3. If a high titer of amoeba antibodies can be found in the serum of symptomatic patients, it is also a strong evidence for the diagnosis of this disease. ^[2]

Amoebiasis test

1. Fecal examination: The stool is dark red with faeces, blood, pus, or mucus.

2. Sigmoidoscopy: If the stool test is negative, sigmoidoscopy has great diagnostic value. The ulcer is usually superficial and covered with yellow pus. The edge of the ulcer is slightly protruding and slightly congested. Scraping material from the ulcer surface for microscopic examination reveals more opportunities for pathogens.

3. Amoebic liver abscess: Abdominal B-ultrasound revealed lesions.

Differential diagnosis of amoebiasis

It should be distinguished from intestinal diseases caused by other causes, especially bacterial dysentery. Intestinal tuberculosis, schistosomiasis, colitis, colon cancer and other intestinal protozoal infections can also be confused with intestinal amebiasis. Ulcer disease, gallbladder disease, and colon polyps must be distinguished from those with unclear abdominal pain and intestinal bleeding. The comprehensive use of the above diagnostic methods is not difficult to identify.

Amoebiasis Treatment

1, general treatment: pay attention to rest, eat a semi-liquid, low-residue, high-protein diet.

2. Pathogen treatment: metronidazole or metronidazole: it is an anti-trichomonas drug, which has a strong killing effect on amoeba trophozoites invading tissues and is relatively safe. It is suitable for all types of intestines and intestines Amoebiasis. The dosage is 600-800mg, taken orally, 3 times a day, continuously for 5-10 days; for children, 50mg / kg / day, divided into 3 times for 7 consecutive days. Nausea, abdominal pain, dizziness, and palpitation occasionally occur during medication, and no special treatment is required. Avoid alcohol during the medication period, as it can cause confusion. Not to be used by pregnant women and breastfeeding women within 3 months. ^[1]

Prognosis of amoebiasis disease

Prognosis is good after timely treatment of intestinal amoebiasis. Such as complicated intestinal hemorrhage, intestinal perforation and diffuse peritonitis, and those with metastatic abscess of liver, lung and brain, the prognosis is poor.

Prevention of amoebiasis disease

Boiling, filtering, disinfecting drinking water, preventing eating lettuce and preventing contamination of the diet, proper disposal of feces, preventing fly breeding and flies are all important measures. It is extremely important to examine and treat cyst-extractors and chronic patients in the catering industry.

Amoebiasis disease care

1. Isolation of the digestive tract.

2. Condition observation: observe the frequency, shape and color of stool.

3. Attention should be paid to the collection of fecal specimens: collect fresh stools in time, select the parts with mucus, pus and blood for timely inspection, and pay attention to insulation. ^[3]

Expert opinion on amoebiasis

With the improvement of China's health conditions and the improvement of people's living standards, the incidence of amoebiasis has decreased significantly, but patients are often seen in outpatient clinics and have been taking medicines for months and years. Infants only a few months old were diagnosed with amoebiasis and given antibiotic treatment. Therefore, it is important to pay attention to the medical history when diagnosing the disease. For example, infants (especially urban babies) are basically not likely to come into contact with the amoeba cysts in the lysed tissue unless they are closely related to the disease. In addition, not every This kind of amoeba can be pathogenic, but the child is therefore given long-term antibiotic treatment, which in turn causes disturbance of the intestinal flora and causes diarrhea.