amoibos (gr. changing), changelings
The term “amoebae” refers to animal unicellular organisms (so-called protozoa) that do not have a solid body shape. Amoebae can constantly change their body structure through the formation of pseudopodia and move in this way.
As unicellular organisms belonging to the group of protozoa, amoebae are counted among the so-called primitive animals. They are about 0.1 to 0.8 mm in size. In most cases amoebae are present as naked unicellular organisms.
However, there are also genera that have a kind of shell (so-called thecamoebae). Amoebae are further subdivided into different genera by different categories. While most of these amoebae genera are completely harmless to humans, amoebae of the genus histolytica can cause severe diseases.
Especially gastrointestinal diseases, which can be accompanied by severe diarrhoea, are caused by this amoeba genus. Furthermore, amoebae can form asymptomatic cysts or the so-called amoebic liver abscess in the human body. A basic distinction must be made between two life forms in amoebae.
The so-called trophozoites settle mainly in the human gastrointestinal tract. The second form of life, the amoeba, is an infectious cyst, which can be excreted in the stool by the infected person and thus be transmitted to other living beings. histolytica, which is dangerous for humans, is widespread in the tropics and subtropics.
In these regions it can be assumed that about 70 percent of the population is a carrier of the pathogen. In Central Europe, diseases caused by amoebae are rather rare. If, however, a corresponding symptomatology develops after a stay in the tropics or subtropics, the treating physician should be informed about the stay abroad.
Pathogenicity – Damage to health of amoebae
Most amoeba genera are completely harmless to humans. Only a few amoebae are described as facultative human pathogenic (possibly damaging to humans). Among the most dangerous amoebae for the human organism are those unicellular organisms which are classified as belonging to the genus Entamoeba histolytica.
They are the triggers of the so-called amoebic dysentery, a serious disease that leads to severe watery diarrhoea in those affected. Furthermore, it must be noted that many amoeba genera carry pathogenic germs such as legionella. The absorption of infected, actually harmless amoebae into the human body can thus cause Legionella-specific diseases. In addition, the amoeba genera Naegleria, Balamuthia and Sappina can lead to severe meningoencephalitis (inflammation of the brain and meninges, meningitis).
Amoeba dysentery is a serious diarrhea disease that occurs mainly in tropical and subtropical regions. The trigger for this disease is exclusively the amoeba genus Entamoeba histolytica. Purely statistically it can be assumed that in the critical regions about one in ten is infected with the amoebae that cause amoebic dysentery.
An estimated 100,000 deaths per year can be linked to this diarrhoea disease. Due to the increasing number of tourists in these areas, the pathogen now occurs worldwide. In Germany, up to 200 cases of amoebic dysentery have been recorded in recent years.
In amoebic dysentery, a differentiation must be made between different forms, which differ in their symptoms and characteristics. In a symptomless intestinal infection (so-called intestinal lumen infection), the causative amoebae only settle in the interior of the intestinal tube. This form of infection usually causes no symptoms.
In invasive intestinal amoebic dysentery, on the other hand, the intestinal tissue is also infiltrated by amoebae. Affected persons develop pronounced symptoms in the course of this infection. The so-called extraintestinal amoebic dysentery is the most serious form of the disease. Amoebae can also be found outside the tissues of the affected persons. In this way, in addition to the typical diarrhoea, liver or brain abscesses can also develop.