amebiasis



OVERVIEW

Definition

Amebic enteropathy is a disease caused by the parasitization of the colon by lysed amoebae, with the main sites of disease being the proximal colon and ileum.

In the life cycle of amebas, there are two forms: trophozoite and encapsulated, with the trophozoite being the pathogenic form and the encapsulated form being the infectious form.

Amebic enteropathy is also known as intestinal amebiasis or amoebic dysentery.

The main sites of disease are the ileum and proximal colon, which are prone to recurrence and chronicity [1-3].

Types

According to the clinical manifestations, it is divided into the following types.

Asymptomatic type (encapsulated carrier)

Mostly asymptomatic, multiple fecal examinations may reveal amoebic encapsulation in lysed tissue.

Acute amoebic dysentery

Symptoms are mild, fecal examination can find lysed tissue amoebic trophozoites and encapsulation.

Most of the slow onset, systemic symptoms of toxicity is mild, can be in the onset of a few days to a few weeks after the spontaneous remission, untreated or incomplete treatment is easy to relapse or become chronic.

Rarely, it is seen in immunocompromised people, and if not rescued in time, it can lead to death within 1 to 2 weeks due to toxicity or complications.

Chronic amoebic dysentery

Chronic amoebic dysentery occurs when clinical symptoms persist for more than 2 months in acute patients.

Incidence

The disease is endemic globally, with a greater incidence in tropical and subtropical regions, where there are some endemic areas.

Poor socio-economic conditions, poor sanitation facilities, harmless disposal of feces is not fully implemented, public water bodies contaminated by feces and poor personal hygiene habits, such as underdeveloped areas are usually more than developed areas.

The incidence of the disease is higher in summer and fall, and is mostly sporadic.

The incidence is higher in mobile populations and travelers are susceptible to the disease [3].

Causes

Causes

Source of infection

Asymptomatic encapsulated carriers, chronically infected patients and recovering patients are the main infectious sources of the disease.

Patients in the acute stage mainly excrete trophozoites that are weakly resistant to the outside world and are not an important source of infection [1-3].

Transmission

The main mode of transmission is oral, mainly through eating food and water contaminated with encapsulated trophozoites.

Contaminated hands and flies can carry the protozoa.

Direct invasion of the skin and mucous membranes by the trophozoites is very rare.

Susceptible population

The population is generally susceptible, but infants and children are relatively less likely to develop the disease.

Malnourished, immunocompromised and immunosuppressed individuals are more likely to develop the disease and are more severely affected.

High titers of specific antibodies in the population do not protect against the disease, and repeated infections are possible [2-3].

Pathogenesis

After oral intake of food and water contaminated by ameba capsules in lysed tissues, it passes through the stomach, and the capsules that are not killed by gastric juice will enter the lower part of the small intestine, and four trophozoites will escape from the capsule under the action of trypsin, and the immature trophozoites will develop while ingesting, and then gradually migrate downward to the ileocecal part and the proximal colon and other parts of the parasitism.

Once the intestinal wall tissue is invaded, it can reproduce in large numbers and cause disease.

Amebic trophozoites in lysed tissues mainly cause damage to the host through deformation, activity, adhesion, enzyme lysis, cytotoxicity and phagocytosis and other contact killing mechanisms, resulting in the rapid death of the target cells, and at the same time, secrete enterotoxin-like substances, causing increased intestinal peristalsis and intestinal spasm, which leads to abdominal pain and diarrhea.

Symptoms

Main Symptoms

The incubation period is usually 3 weeks, but can be as short as a few days or as long as more than a year, and the symptoms of each type are as follows [1-3].

Asymptomatic type (encapsulated carrier)

Clinical symptoms are usually absent.

Multiple fecal examinations may reveal amoebic encapsulation in lysed tissue.

It may turn into acute type when the immunity of the organism decreases.

Acute amoebic dysentery

Clinical symptoms are mild, mainly abdominal pain and diarrhea.

Intestinal lesions are mild, and symptoms of dysentery may appear when the body’s immunity is reduced.

Mostly slow onset, mild systemic symptoms, no fever or low-grade fever, abdominal discomfort, diarrhea.

Typical manifestations are mucous bloody stools, jam-like, 3 to more than 10 times a day, accompanied by a fishy odor, may have abdominal distension or mild to moderate abdominal pain.

There may be abdominal distension or mild to moderate abdominal pain. When the lesion involves the rectum, there may be a sense of urgency and heaviness.

It is very rare, and most common in immunocompromised people, such as malnutrition, weakness, pregnant women, severe infections, use of glucocorticoid therapy and other people.

The onset of the disease is rapid and the symptoms of toxicity are severe. There may be high fever, severe intestinal colic, followed by the discharge of mucous bloody or bloody watery stools more than ten times a day, accompanied by a sense of urgency and heaviness, and a large amount of fecal matter.

There may be nausea and vomiting, and there may be circulatory disturbances and impaired consciousness due to dehydration.

Chronic amoebic dysentery

May present with lack of appetite, malaise, anemia, and abdominal distension. There may be hyperactive bowel sounds and mild pressure pain in the right lower abdomen.

Symptoms may be persistent or intermittent, with intervals of varying length during which no symptoms may be present.

Complications

Complications of amebic enteropathy can be broadly categorized into intestinal and extraintestinal complications [1-2].

Intestinal complications

Amebas parasitizing the intestinal wall in lysed tissue can cause intestinal mucosal ulcers, and when the ulcers reach the muscularis propria and invade the blood vessels, they can lead to intestinal bleeding of different degrees.

Superficial ulcers may ooze blood and cause small amounts of intestinal bleeding, which may lead to bloody stools.

When the ulcer reaches the submucosal layer and encroaches on the large blood vessels or granuloma destruction, it can cause a large amount of intestinal bleeding, resulting in dark red or bright red loose stools, and in severe cases, it can cause hemorrhagic shock.

It is the most serious complication, which can be life-threatening, and is most common in fulminant cases and those with deep ulcers, and perforation is most common in the cecum, appendix and ascending colon.

It can cause limited or diffuse peritonitis, which can result in severe abdominal pain and signs of peritoneal irritation (abdominal muscle tension, abdominal pressure, rebound pain).

Can also lead to chronic perforation, the formation of adhesions, and then the formation of local abscess or penetrate into the neighboring organs to form an internal fistula, usually abdominal pain symptoms are not obvious, but progressive abdominal distension can occur, there may be a loss of intestinal sounds, local peritoneal irritation signs and other signs.

Lysed tissue ameba parasites in the cecum is easy to spread to the appendix, causing amebic appendicitis.

Metastatic right lower abdominal pain, pressure pain and rebound pain at Mai’s point (the junction of the right anterior superior iliac spine and the middle and outer 1/3 of the umbilical cord line) can be seen, which is similar to the clinical manifestations of general appendicitis, but is more prone to perforation than general appendicitis.

Lysogenous tissue ameba parasitism in the colon can lead to ameboma, granuloma and fibrous stenosis and other proliferative lesions in the colon, the lesions are located in the cecum, sigmoid colon and rectum and other places.

In some cases, complete intestinal obstruction or intussusception may occur, resulting in symptoms such as abdominal distension, constipation, anal cessation of bowel movement and defecation, nausea, and vomiting.

Lysed tissues within the amoebic trophozoites can invade the surrounding tissues and organs from the rectum, forming rectal-perianal fistula or rectal-vaginal fistula.

Fecal-smelling pus often flows out of the mouth of the tube.

Extra-intestinal complications

After parasitizing the intestinal tract with amebic trophozoites in lysed tissues, they can migrate through the veins of the intestinal wall, lymphatic vessels or spread directly, and spread to other parts of the body such as the liver, the abdominal cavity, the lungs, the pleura, the mediastinum, the pericardium, the brain, the genitourinary system, or the neighboring skin.

It can cause inflammation, abscess or ulceration in the corresponding parts, such as amebic liver abscess, amebic lung abscess, amebic brain abscess, amebic pleurisy, etc., among which amebic liver abscess is the most common.

Consultation

Department of Medicine

Department of Infectious Diseases

When symptoms such as fever, abdominal pain, diarrhea, mucous blood stools, bloody watery stools occur, it is recommended to consult a doctor promptly.

Emergency Medicine

When symptoms such as severe abdominal pain, large amount of mucous bloody or bloody watery stools, generalized weakness, profuse sweating, irritability, fainting, etc. occur, it is recommended to consult a doctor immediately.

Preparation for medical treatment

Preparation for medical consultation: registration, preparation of documents, common problems

Tips for seeking medical treatment

Record the number, duration and nature of diarrhea for the doctor’s reference.

Record the change of body temperature for doctor’s reference.

Preparation Checklist

Pay special attention to the time of onset of symptoms, special manifestations, etc.

Is there any abdominal pain? Where is the location of the abdominal pain? Is it distended, vague or colicky?

What is the timing, frequency and duration of the episodes of abdominal pain?

Do you have diarrhea? How many times a day do you pass stools? What is the approximate amount each time?

Is there blood or mucus in the stool?

Is there any fever? What is the highest temperature?

Is there any lack of appetite, fatigue, etc.?

Any history of traveling or eating cold food before the onset of the illness?

Was there any contact with patients with chronic diarrhea before the onset of the illness?

Are there any immune disorders, hormone therapy, malnutrition, severe infections, etc.?

Test results in the last six months, which can be brought to the doctor’s office.

Laboratory tests: stool routine, blood routine

Imaging test: X-ray barium enema examination

Others: Colonoscopy

Medication in the last 3 months, if available, bring the box or package to the doctor

Pathogenic treatment drugs: metronidazole, tinidazole, ornidazole, etc.

Diagnosis

Diagnosis based on

History of illness

There may be a history of travel or a history of eating cold food or contact with patients with chronic diarrhea prior to the onset of the disease.

Clinical manifestations

The onset of the disease is mostly slow, often no fever or only low fever, abdominal pain, diarrhea (dark red jam-like stools, up to 3 to 10 times a day, each time the stool is more, may have a fishy smell), often without a sense of urgency and heaviness.

There may be obvious pressure pain in the right lower abdomen and hyperactive bowel sounds.

Laboratory examination

After adding saline smear and microscopic examination, a large number of clumped red blood cells, a small number of white blood cells, etc. can be seen.

Microscopic examination shows active trophoblasts that phagocytose erythrocytes, which are identified as amebas in lysed tissues and are of diagnostic value.

Antibodies can be detected in patients infected with amebas in lysed tissues of more than 1 week’s duration, and the detection methods include convective immunoelectrophoresis, enzyme-linked immunosorbent assay, and so on.

If the serum is positive for specific IgG antibodies, it helps to diagnose the disease. Positive specific IgM antibodies are indicative of recent or current infection, while negative antibodies do not exclude the disease.

DNA probe hybridization technique, polymerase chain reaction (PCR) can be used to detect the DNA of amoebic trophozoites in the feces, pus, or blood of the patient, and if positive, it can be used as the basis for the diagnosis of the disease.

Colonoscopy

Colonoscopy reveals scattered submerged ulcers of varying sizes with slightly elevated margins, red halos, and mostly normal interulcer mucosa.

Under colonoscopy, specimens can be scraped from the ulcer surface for microscopic examination, and there are more chances of finding pathogens.

X-ray barium enema

It can visualize the lesion pattern in the intestine.

It is valuable for causing intestinal stenosis, amoeboma and other colonic lesions.

Differential diagnosis

Bacterial dysentery

Similarity: both can cause fever, abdominal pain, diarrhea and other symptoms.

Differences:

Bacteriophageal dysentery is mostly acute in onset, with small amount of stool per evacuation, mostly mucopurulent blood-like stools, little fecal matter, common pressure pain in the left lower abdomen, acute and severe, and a large number of red blood cells, leukocytes and pus cells can be seen in the stool routine, and culture can have dysentery bacillus growth.

Amebic enteropathy mostly slow onset, each bowel movement is more, mostly jam-like stools, fecal matter, common in the right lower abdominal pain, stool routine can be seen in lysed tissues within the amoebic trophozoites or encapsulated.

Bacterial food poisoning

Similarities: both can have a history of unclean diet before the onset of the disease, both can cause abdominal pain, diarrhea and other symptoms.

Differences:

Bacterial food poisoning has a rapid onset, short incubation period, mostly several hours, small amount of feces each time, the onset of the same eater often at the same time or successively, pressure and pain around the umbilicus, large amount of feces each time, more severe symptoms of intoxication, and the culture of the remaining food, vomitus, or fecal matter can have pathogenic bacteria growth.

Amebic enteropathy is mostly slow onset, the incubation period is usually 3 weeks, but can be as short as a few days or as long as more than a year, mostly jam-like stools, fecal matter, to the right lower abdominal pain is common, fecal routinely see lysed tissues within the amoebic trophozoites or encapsulated.

Schistosomiasis

Similarities: both can cause fever, abdominal pain, diarrhea and other symptoms.

Differences:

Schistosomiasis has a history of contact with infected water, in addition to the above symptoms, there are symptoms such as caecal dermatitis, hepatomegaly, defecation less than 10 times a day, mostly mucous bloody stools, thin feces, to the left lower abdominal pressure and pain is common, fecal routine can detect schistosomal eggs or hatching of trichuris trichiuria, and schistosomal circulating antigens or antibodies are positive.

Amoebic enteropathy is more voluminous per bowel movement, mostly jam-like stools, fecal matter, fecal routine can see lysed tissue within the amoebic trophozoites or encapsulated, blood amoebic antibody positive.

Others

It also needs to be differentiated from intestinal tuberculosis, rectal cancer, colon cancer, chronic non-specific ulcerative colitis, etc., and most of them can be diagnosed with the assistance of colonoscopy.

Treatment

Aim of treatment: eliminate pathogens, cut off transmission channels, prevent and reduce complications.

Treatment principle: general treatment, symptomatic treatment and pathogenic treatment.

General treatment

Acute patients should rest in bed, and can eat liquid or less residue diet.

Chronic patients should strengthen nutrition and avoid eating irritating foods, such as chili peppers.

Intestinal isolation is needed until clinical symptoms disappear and fecal examination fails to find trophozoites and encapsulated bodies for 3 consecutive times (1 time every other day).

Symptomatic treatment

Appropriate fluid replacement can be used to maintain water-electrolyte balance in case of severe diarrhea, vomiting or persistent fever.

Pathogen treatment

The following classes of antilysosomal intratissue amoebic drugs are currently in common use:

Nitroimidazoles

For the first choice of drugs, the ameba trophozoites have a powerful killing effect.

Commonly used drugs include metronidazole and tinidazole.

There can be transient leukopenia and neurological disorders such as dizziness, vertigo and ataxia.

It is contraindicated in pregnant and lactating women, those with a history of hematologic disorders and neurological disorders.

Antimicrobials

For patients with severe amoebic dysentery, especially when combined with bacterial infections, antimicrobial drugs are required on top of the application of anti-amoebic drugs.

Commonly used drugs include baloneycin or quinolone (e.g., levofloxacin, norfloxacin) antibacterial drugs.

Prognosis

Cure

The prognosis is good for patients without complications and who receive timely and effective antipathogenic therapy.

Patients who are not treated promptly and thoroughly, are heavy, and cause serious complications have a poor prognosis [1-3].

Prognostic factors

The prognosis of amebic enteropathy is related to a number of factors, and the following factors often lead to a poor prognosis.

Failure to receive prompt and effective treatment.

Inadequate treatment.

Severe amebic enteropathy.

Complicated extra-intestinal amebiasis that is not properly diagnosed and treated.

Daily

Daily Management

Dietary management

Acute patients can eat fluid or less residue diet, such as congee and noodles.

Chronic patients should strengthen nutrition and avoid stimulating foods, such as chili peppers and mustard.

Separate raw and cooked utensils to prevent food from being contaminated. Drinking water should be boiled and no raw or cold food should be eaten.

Life management

In acute stage, bed rest should be provided.

Pay attention to personal hygiene, wash hands before and after meals.

Change the contaminated bed sheet in time, keep the bed sheet dry and tidy.

Disease monitoring

For diarrhea, observe and record the number of times of diarrhea, whether there is mucus and blood stool, and whether there is fecal odor liquid coming out from the perianal area.

For vomiting, observe whether there is blood vomiting and the number of times of vomiting.

For those with fever, learn the correct way to measure body temperature, and monitor and record changes in body temperature.

Prevention

Management of infectious agents

Early detection and treatment of asymptomatic carriers of amoebic encapsulation in lysed tissues and patients with amoebiasis.

If any of them work in the catering industry, they should be transferred out of their jobs during treatment.

Cutting off the means of transmission

Eliminate the breeding places of flies and cockroaches, pay attention to food hygiene, and preferably soak raw vegetables in boiling water first.

Strengthen the management of water sources and carry out harmless treatment of feces, garbage and sewage.

Strengthen hygiene education for the public and develop good personal hygiene habits of washing hands before and after meals.

Protecting susceptible people

Adopt good living habits, eat reasonably, do not favor one food over another, and do not stay up late.

Strengthen physical exercise to enhance physical fitness [1-2].