Amoebic dysentery

Amoebic dysentery is a diarrheal disease caused by the pathogen Entamoeba histolytica. It leads to bloody, slimy diarrhea and cramping abdominal pain. The main source of infection is contaminated drinking water

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Amoebic dysentery - briefly explained

Amoebic dysentery is an infectious disease caused by the Entamoeba histolytica parasite. This occurs mainly in tropical and subtropical regions with poor hygienic conditions. The transmission occurs mainly through contaminated drinking water, less often through fruit and vegetables, which came into contact with the pathogen through poor hand hygiene or during fertilization. A smear infection is also possible. The pathogen colonizes the intestine and can even stay there for several years without causing symptoms. If the cyst changes to the minute shape, there are no symptoms or only simple diarrhea, if it changes to the magna shape (see below), the intestinal wall is damaged and the pathogen can spread and, in addition to bloody, watery diarrhea, severe complications such as a liver abscess (encapsulated Accumulation of pus in the liver). This severe course of the disease is called amoebic dysentery. If the disease is diagnosed in good time, it can be treated well with medication. With appropriate antibiotic therapy, the prognosis is very good.

What is amoebic dysentery?

Amoebic dysentery is an infectious disease. Amoebas are unicellular parasites that are mainly found in the large intestine. In the event of an infection by amoebas (amebiasis), a distinction must be made between the intestinal colonization by Entamoeba dispar or moshkovskii, which is harmless to humans, and an infection with Entamoeba histolytica. The latter sometimes leads to the most severe courses (amoebic dysentery) and complications. However, around 90 percent of all amebiasis cases are harmless infections caused by Entamoeba dispar.

Background information - What is the Minuta- and Magnaform?

Entamoeba histolytica goes through two stages: that as an immobile cyst and that as a so-called trophozoite, which can form cysts again.

After the Entamoeba histolytica cysts have been ingested through food or drinking water, they multiply and develop in the intestine into so-called minuta forms (non-hematogenic trophozoites). The trophozoites can multiply through cell division and form cysts again, which are excreted in the stool. In this form of cyst, the pathogens in the environment can remain infectious for a long time.

In some cases, however, the minute forms also transform into so-called magna forms (hematogenic trophozoites). These can penetrate the intestinal mucous membrane of the rectum and large intestine, damage it and move on from there. Only Entamoeba histolytica has the ability to penetrate tissue. These forms of the disease are therefore called invasive forms. Damage to the intestinal wall can lead to widespread ulcers in the colon.

While the minute forms lead to simple diarrhea, the magna forms can cause severe inflammation of the intestinal mucosa (amoebic colitis) with bloody diarrhea. This can lead to serious complications such as threatening bowel enlargement with intestinal perforations, abscesses (encapsulated accumulation of pus), mainly in the liver, and peritonitis. The extent to which symptoms develop depends primarily on the body's defenses and the amount of pathogen absorbed.

Cause: How is the pathogen transmitted?

The infectious cysts of the pathogen are excreted by infected people with the stool and spread - like many diarrhea pathogens - primarily via the drinking water. They are very resilient and can survive permanently outside the body if the environment is sufficiently moist. Although amoeba are found worldwide, infections are rare in developed areas with well-developed sewage systems and good drinking water supplies. The disease spreads rapidly, especially in developing countries where wastewater mixes with the groundwater that is used as drinking water. The frequent use of human excrement as fertilizer, in addition to contamination of the groundwater, leads to the ingestion of cysts by contaminated food.

Distribution: where does amoebic dysentery occur?

It is a globally occurring pathogen that also occurs in the cold climates of the Arctic. However, it is most widespread in tropical regions. The worldwide distribution pattern of the infection rate in the population is strongly influenced by the hygienic conditions, the population density and the local income levels. Developing countries are particularly affected here. In individual areas, up to 90 percent of people are infected. It is estimated that there are more than 50 million diseases worldwide. Port cities and coastal areas such as the west coast of Africa or the coast of northern Brazil as well as slum areas in India and Bangladesh are often severely affected. There is also a high infection rate in the humid areas of Southeast Asia. During outbreaks in these regions, a weakened immune system of those affected, often caused by malnutrition, also plays a role. Under appropriate conditions, epidemics can occur here.

Symptoms: what symptoms does amoebic dysentery cause?

The timing of the infection is very variable. In most cases, the first symptoms appear between one and four weeks after ingestion of the pathogen. Over the course of several days, the symptoms increase slowly with changing intensity. The spectrum ranges from a symptom-free infection to full symptoms of amoebic dysentery and impending complications.

The main symptom is diarrhea. In uncomplicated cases, these occur differently and frequently and are regularly accompanied by cramp-like abdominal pain. Usually the sick person is doing relatively well. If mucus and blood are added (dysentery), a severe infection can be assumed. The bowel movement is also referred to as raspberry jelly-like here. The cramp-like abdominal pain increases sharply, with fever, chills, headache and nausea. The diarrhea increases.

Mild forms of the disease, if they persist over a longer period of time (chronic course with varying diarrheal symptoms), can lead to fatigue, weight loss and listlessness.

The course of the disease becomes drastically more difficult when complications such as an intestinal rupture or an amoebic liver abscess are added. When the intestine ruptures (intestinal perforation), the intestinal wall breaks through in the area of ​​an amoebic ulcer and causes severe inflammation of the abdominal cavity and the peritoneum (peritonitis). Occasionally abscesses (encapsulated collection of pus) appear in the abdomen and other organs. The pathogen can colonize other organs, preferably the liver, via the bloodstream. One or more abscesses that are filled with fluid develop in the liver. The amoebic liver abscess can occur years after infection and is a serious, life-threatening disease that requires inpatient treatment.

Diagnosis: how can amoebic dysentery be determined?

An amoebic infection can be determined by microscopic detection of cysts or trophozoites in the stool. However, the doctor cannot differentiate between a harmless Entamoeba dispar infection and an Entamoeba histolytica infection that requires treatment. Exception: Magnaforms (haematogenic trophozoites) that only occur in Entamoeba histolytica infections are rarely detected.

Various special stool examinations are available to differentiate between the two types of amoeba. Since pathogens are not always excreted, several stool samples may have to be taken on different days. The most important method is the ELISA (enzyme-linked immunosorbent assay). It is used to detect characteristics typical of parasites, so-called antigens. With the polymerase chain reaction (PCR) parasite-specific gene components can be determined. Furthermore, a cultural cultivation is also an option.

The determination of antibodies in the blood, which are usually already present at the beginning of the symptoms, can also be helpful. If there is a suspicion that the pathogen is already spreading in the body, further blood values ​​(such as inflammation markers) are determined.

An amoebic liver abscess is associated with the detection of antibodies and usually with slightly increased liver values ​​and significantly increased inflammation values ​​and can be easily detected using imaging methods such as sonography, computed tomography (CT) or magnetic resonance tomography (MRT).

Therapy: How can amoebic dysentery be treated?

The nitroimidazoles metronidazole, tinidazole, nimorazole and ornidazole are available for treatment with antibiotics. In Germany, doctors mainly use metronidazole. Therapy is usually carried out over seven to ten days. In severe cases, it should be administered as an infusion. This group of antibiotics (the nitroimidazoles) mainly acts against pathogens in the tissue, and only to a small extent in the intestine. Sick people who shed cysts should then take the aminoglycoside antibiotic paromomycin or the active ingredient diloxanide furoate for several days. The patient's condition usually improves rapidly with antibiotic therapy. The anticonvulsant N-butylscopolamine can also help against the cramp-like abdominal pain, but doctors only use it if there are no contraindications.

An amoebic liver abscess can often be treated purely with medication, but it can also require surgical therapy or puncture of the abscess.

Prevention: How can you protect yourself from amoebic dysentery?

Amoeba infection is the most common parasite infection that occurs in travelers. Since the disease is mainly transmitted through water, vacationers should pay particular attention to drinking water hygiene. In the respective travel countries you should not take water from the tap or open vessels into your mouth - not even when brushing your teeth. Boiling and sufficient filtration are suitable to rid the water of amoebic cysts. Chlorination alone is not enough.

If plants are fertilized with feces, they can often not be cleared of cysts even by washing. Travelers should therefore avoid salads and other raw vegetables. Fresh fruit that you peel yourself, on the other hand, is considered safe. The general advice is: "Boil it, cook it, peel it or forget it!", In English: "fry it, boil it, peel it or forget it!".

In general, the risk of infection depends on the individual travel behavior. Those who visit luxurious hotels and restaurants with a high hygienic standard have a significantly lower risk of infection than a backpacker who eats food in local cookshops and street stalls. There is currently no vaccination. Experts do not consider the preventive use of antibiotics to be sensible.

Dr. med. Markus N. Frühwein

© W & B / private

Our advisory expert:

Our author Dr. med. Markus Frühwein, has his own practice in Munich and is director of the Bavarian Society for Immune, Tropical Medicine and Vaccination e.V.

Swell:

  • AWMF, S1 guidelines for diagnosis and treatment of amebiasis, status 10/2018. Online: https://dtg.org/images/Leitlinien_DTG/Leitlinie_S1_Amoebiasis_Diagnostik-Therapie_102018.pdf (accessed on November 6, 2019)
  • Robert Koch Institute (RKI), amoebic infection. Online: https://www.rki.de/DE/Content/InfAZ/A/Amoeben-Infktionen/Amoeben.html (accessed on November 6, 2019)
  • Centers for Disease Control and Prevention (CDC), Parasites - Amebiasis - Entamoeba histolytica Infection. Online: https://www.cdc.gov/parasites/amebiasis/general-info.html (accessed November 6, 2019)

Important note: This article contains general information only and should not be used for self-diagnosis or self-treatment. He can not substitute a visit at the doctor. Unfortunately, our experts cannot answer individual questions.

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