Brief overview
- Symptoms: Symptoms differ depending on whether one has what is called intestinal or extraintestinal amebiasis and include bloody diarrhea, abdominal cramps, fever, and pus formation in the liver.
- Treatment: specific antibiotics are available to treat amebic dysentery.
- Cause: The transmission of the parasites is fecal-oral, i.e. through the ingestion of cysts excreted in the stool.
- Risk factors: Infection is particularly likely in developing countries. Risk factors include low standards of hygiene, but also, for example, anal-oral sexual intercourse.
- Diagnosis: In addition to blood and stool tests, other examination methods such as ultrasound, MRI and CT are available for diagnosis.
- Prognosis: Amoebic dysentery is considered completely curable if treated properly.
- Prevention: The probability of contracting amoebic dysentery can be reduced by appropriate hygiene measures.
What is amoebic dysentery?
Amoebic dysentery is caused by the protozoan “Entamoeba histolytica”. It is not the only amoeba that affects humans, but it is the only one that makes them sick. The amoebae that do not (E. dispar, E. moshkovskii) are much more common.
Entamoeba histolytica and E. dispar together form the so-called “E. histolytica/E. dispar complex”. It is estimated that about half a billion people worldwide carry both species at the same time. Of these individuals, however, the majority are infected by the non-pathogenic E. dispar.
About 50 million people fall ill with amoebic dysentery every year, of whom a maximum of 100,000 die as a result of the infection.
Not every infected person also falls ill with amoebic dysentery.
More than 90 percent of parasite carriers never develop symptoms. However, since they still excrete disseminated stages (cysts) in their stool, they incessantly infect other people. Only when the amoebae manage to leave the intestine and enter the bloodstream do they cause life-threatening damage to other organs.
What is an amoeba?
An amoeba is a parasite that belongs to the group of protozoa and feeds primarily on red blood cells in the human body. A much better known protozoan disease is malaria. Amoebiasis is transmitted by the cysts of the amoebae.
These spherical surviving stages are much more robust than the motile form of the amoebae and thus increase the likelihood of transmission. They dry out slowly outside the intestine and do not require food.
Either they develop into cysts and are excreted again in the stool, or they attack the intestinal wall. If they are excreted and ingested by another person, the cycle is closed.
If the intestinal wall is attacked in amoebic dysentery, abdominal pain with bloody diarrhea results. In rare cases, the amoebae enter the bloodstream and are carried to different organs.
Due to the battle between the immune system and the amoeba, there is then a lot of pus formation inside the organ. Doctors then speak of an abscess.
How do you get infected with amoebic dysentery?
Infected people constantly excrete cysts. If these cysts get into drinking water or onto food that is eaten raw, others may become infected by consuming the contaminated food or water.
Transmission is especially likely via:
- Fruits and raw vegetables
- @ Water and beverages
- Ice cream or sherbet
- Salad
Generally, a moist, dark environment is ideal for cysts. In such a habitat, they survive for several weeks in drinking water or on food. Even short trips to high-risk countries are enough to become infected with amoebic dysentery. In high-risk areas, about half of the resident population is infected.
Where does amoebic dysentery occur?
Wherever there are no high hygiene standards, there is a risk of transmission of amebiasis. This applies in particular to developing countries. Infection is common in Central and South America, Africa and South Asia, but it also occurs in Western countries.
What are the symptoms?
Most people infected with the amoeba E. histolytica do not show any symptoms of amoebic dysentery. A pure infection without symptoms is referred to as an infestation.
About ten percent of cases develop what is called “intestinal amebiasis,” in which the amoebae invade and colonize the intestinal wall.
In only one percent of cases do the amoebae enter the bloodstream and colonize organs such as the liver. Abscesses form in these organs, limiting organ function, and thus leading to death in the worst case.
If the parasites move from the intestine to other parts of the body, doctors refer to this as “extraintestinal amebiasis.”
Intestinal amebiasis
Intestinal amebiasis is amebic dysentery in the narrow sense. The onset of amebic dysentery is rather insidious. One to several weeks after infection, mucopurulent, sometimes bloody diarrhea and abdominal cramps occur six to eight times a day.
Since other diagnoses such as bacterial diarrhea or appendicitis are more common than amebic dysentery in Western countries, it is important to inform the physician if affected individuals have recently been on a tropical trip.
If intestinal amebiasis is not recognized, symptoms persist. They are easily confused with inflammatory bowel diseases such as Crohn’s disease or ulcerative colitis. Both diseases involve a faulty reaction of the immune system against the intestine, in which repeated diarrhea and abdominal pain also occur.
If misdiagnosed, amoebic dysentery threatens further complications. The inflammation may cause nodules in the intestinal wall that interfere with stool passage. If this is the case, doctors speak of intestinal obstruction (ileus).
In rare cases, the intestine may burst, with serious consequences for the patient and his or her life. There is also a risk of the amoebae entering the bloodstream and causing extraintestinal amebiasis.
Extraintestinal amebiasis
If the amoebae enter the bloodstream, they reach just about every organ. Most commonly, they migrate from the intestine to the liver. This occurs months to years after infection and occurs even without prior diarrhea symptoms or regular abdominal pain.
The infection sometimes breaks through from the liver to the chest and heart. Although the amoebae reach the liver through the intestines, diarrhea occurs in only 30 percent of abscess patients. This means that even without abdominal pain and diarrhea, amoebic infection is possible.
How is amebic dysentery treated?
In the treatment of amebic dysentery, it plays an important role whether the amoebae have already damaged the intestinal wall or whether it is an asymptomatic infestation. Both require medical treatment to avoid later complications and to limit the spread of amoebic dysentery as efficiently as possible.
Infestation without symptoms:
If E. histolytica has been detected in the stool without symptoms of amoebic dysentery and without evidence of organ damage, therapy with the antibiotic paromomycin for about ten days is sufficient. The substance is not absorbed into the body and thus kills only the amoebae in the intestine.
Infection of the intestinal wall (intestinal amebiasis):
If the amoebae have infected the intestinal wall, there is usually bloody, mucous diarrhea. If this is the case, amebic dysentery is treated with metronidazole in addition to paromomycin. The physician uses a stool sample examination to check whether the treatment was successful.
Amoebic abscess:
In severe courses of amoebic infection, the patient may need to be stabilized before definitive therapy is possible. If the affected person is severely ill, the physician must decide, depending on the organ and the patient, exactly how to proceed in order to save the patient’s life.
Amoebic dysentery: causes and risk factors
Looking at all the ways amoebic dysentery is transmitted, it is clear that the main risk factor is the hygienic conditions of the particular region.
When traveling to affected regions, special attention should be paid to the hygiene of drinking water and food. One’s own behavior in tropical and subtropical countries accounts for a large part of the risk of contracting the disease.
Another route of infection is anal-oral sexual intercourse. In this case, the cysts pass directly from the rectum into the mouth of the sexual partner.
In addition, there is also an increased incidence of the disease:
- young children
- older people
- pregnant women
- patients under cortisone therapy
- immunocompromised patients
- malnourished people
For these people, complications such as a liver abscess are often more serious than for other patients. Early diagnosis and consistent therapy may prevent the spread of amoebae.
Examinations and diagnosis
The first step is a direct discussion with the patient (anamnesis). Past trips to risk areas should be mentioned, as should acute complaints. The physician asks the following questions:
- Have you recently been to a tropical country?
- Do you have diarrhea and if so, for how long?
- Is your diarrhea bloody-mucous?
Even though the trip abroad may have been years ago, it is important to tell your doctor about the trip so that he or she can make a tentative diagnosis of amebic dysentery.
Detection of amoebic dysentery is done using a stool or tissue sample from the intestine (intestinal biopsy) that the doctor or lab technician looks at under a microscope. However, it is usually not possible to distinguish between malignant E. histolytica and other amoebic species in this way.
However, there are special methods that detect either certain components of the amoebae, so-called amoebic antigens, or the genetic information (DNA) of E. histolytica in the stool.
Blood tests are also available to detect antibodies in the blood that the patient’s immune system has produced in the event of infection against E. histolytica.
A blood test also becomes important when extraintestinal amebiasis is suspected. In the case of extraintestinal amebiasis, cysts are not necessarily found in the stool, but only the amoebae in the affected organs.
If organs other than the intestine are affected, ultrasound and, if necessary, computed tomography (CT) or magnetic resonance imaging (MRI) can be used to view the abscess in an image.
The physician does not have to report the amoebic dysentery to the health department. However, if cases accumulate among his patients, it is very much reportable. This is how the legislator tries to efficiently limit possible outbreaks of amoebic dysentery in Germany.
Amoebic dysentery: course of the disease and prognosis
The course of amoebic dysentery is very diverse. Infection with E. histolytica does not make everyone sick. Even if one does become ill, symptoms range from simple diarrhea to a life-threatening liver abscess.
In any case, a known infection should always be treated consistently to protect oneself and others. If this is the case, amoebic dysentery is now considered a completely curable disease. About 100 years ago, amoebic dysentery was still a major health problem in Germany.
However, if amoebic dysentery is not treated, one contributes to the spread of the disease, and it may eventually lead to the dangerous organ infestation, which is potentially life-threatening.
The two drugs against amoebic dysentery are well tolerated and promise a complete cure if the disease is detected and treated early enough.
To prevent amoebic dysentery, the following rules should be followed when traveling to high-risk areas:
- Peel raw fruit before eating.
- It is best to boil vegetables.
- Do not eat raw meat or raw seafood.
- Do not drink tap water; also do not use it to brush your teeth without boiling it first.
- Chlorinated water is also not protective. If you are unsure, always boil the water as a precaution.
- Be careful with unsealed water bottles in restaurants, as they are often refilled with tap water.
- Also, avoid ice cubes or homemade water ice as well as sherbet.
- Use different condoms during sexual intercourse and oral sex.
By taking these precautions, you will reduce your chances of getting amoebic dysentery. If you suspect that you have caught amoebic dysentery despite all the precautions, see a doctor immediately.
