​Infectious Diseases and Microbiology - Amebic dysentery ( Entamoeba histolytica)

​Infectious Diseases and Microbiology - Amebic dysentery ( Entamoeba histolytica) 
Entamoeba histolytica is a type of single-celled parasite.
There are two stages that are encountered. The trophozoite type of amebae is the exclusive presence in tissue. It is also present in liquid feces with the occurrence of amebic dysentery. The dormant cysts are exclusively found within the colon's lumen and can be observed in soft or solid feces. Both symptomatic and asymptomatic patients excrete cysts in their feces, which can subsequently contaminate food and water sources. The cysts exhibit resistance to chlorination. The primary modes of transmission are by the ingestion of fecal matter and the direct contact of the mouth with the anus.

Infection with E histolytica leads to three distinct symptoms. Several patients are asymptomatic yet continue to be carriers, releasing cysts in their stool. patients who show symptoms may display amebic dysentery, which includes cramps, tenesmus, gas, and feces containing blood and mucus. A tiny portion of these patients may also experience more severe extraintestinal disease, characterized by abscesses, particularly in the liver.

Following the consumption of a cyst (metacyst), the process of excystation commences upon activation. The metacyst undergoes fast division, resulting in the formation of four amebulae, with each amebula corresponding to one cyst nucleus. Subsequently, each amebula undergoes further division, leading to the production of eight tiny trophozoites within each infective cyst. The trophozoites invade the large intestine, resulting in tissue damage and the formation of a distinct flask-shaped ulcer. Further invasion leads to the development of abscesses and the spread of the infection throughout the body.

The stool analysis under a microscope shows trophozoites with ingested red blood cells and cysts with four nuclei, indicating the presence of the parasite. Nonpathogenic species, such as Entamoeba coli, can be differentiated from E histolytica by the presence of cysts that contain eight nuclei. Serum antibody testing can aid in diagnosing amebic dysentery and extraintestinal amebiasis that affects the liver.

Treatment for symptoms of varying severity may involve the administration of metronidazole and luminal amebicides, such as iodoquinol. Control strategies include the implementation of proper hygiene practices, sanitation measures, and educational initiatives aimed at preventing the transmission of diseases.

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