The causative agent of the disease was discovered by F. A. Leshem in 1875 when examining the feces of a patient with bloody diarrhea and named him Amoeba coll . F. A. Lesch considered Amoeba coli to be the causative agent of a special type of dysentery. He also infected four dogs with feces of this patient, one of which got an acute form of amoebiasis with a typical colon lesion and pathogen excretion. In 1883 p. R. Koch, when examining the corpses of people who died from dysentery, isolated an amoeba from intestinal tissues and from liver abscesses. A similar pathogen was isolated by Koch from the feces of some patients with dysentery. The current name for the causative agent of amoebiasis – Entamoeba histolytica – proposed by F. Schaudinn
in 1903 p. For the first time, amoebiasis as an independent infectious disease was isolated by W. Cauncilman and F. Loffler in 1891 under the name amoebic dysentery.
Etiology of Amebiasis
The causative agent of amoebiasis – Entamoeba histolytica – belongs to the genus Entamoeba , family Entamoebidae , such as protozoa – Protozoa . The life cycle of the pathogen of amoebiasis consists of two stages – vegetative and dormancy, or cysts.
At the vegetative stage, three main forms of amoeba are distinguished:
1) large vegetative (tissue)
2) small vegetative (enlightening, commensal ),
3) precystic . The large vegetative (tissue) form is manifested only in svidovidilenye feces of patients with intestinal amoebiasis in the acute period of the disease or with an exacerbation of the chronic form. its protoplasm has two layers: the outer (ectoplasm) and the inner (endoplasm).
The ectoplasmic layer forms pseudopodia, with the help of which the amoeba actively moves and can penetrate the wall of the colon, where it can phagocytose red blood cells ( erythrophage ), which can be seen in the endoplasm. It releases proteolytic enzymes. Outside the body, it is not viable and dies within 20-30 minutes. Small vegetative (gaps a) form of E. histolytica is excreted from feces of convalescents after acute intestinal amoebiasis, patients with chronic form of amoebiasis, cystonosi in the use of laxatives. It has much smaller dimensions, sedentary, ectoplasm, its power to phagocytose red blood cells. Under appropriate conditions, it can turn into a large vegetative form, causing illness. Outside the body, it is not viable and quickly dies. The pre-cystic form is even smaller, oval or round, sedentary, its bypass shell due to compaction of the endo-and ectoplasm. This form is transitional to cystic form. A cyst (resting stage) of a spherical shape, with a diameter of 8-16 microns. Mature forms have four nuclei, and immature ones, one, two or three, unlike Entamoeba soy cysts containing eight nuclei. Cysts are excreted with feces of patients with a chronic form of amoebiasis during remission, healthy cystonosiosis , and also convalescents after acute amoebiasis. Cyst is the only form of Entamoeba histolytica , which is able to stay in the environment for a long time. So, in feces, cysts last for 15 days, in tap water for about one month, in moist soil for 8-10 days, they tolerate low temperatures well, and die at 85 ° C very quickly. Comparison resistant to disinfectants. So, 1% solution of bleach, 5% formalin solution do not have a noticeable disinfecting effect.