Entamoeba histolytica -Introduction, Morphology, Pathogenicity

Introduction

Table of Contents

Entamoeba histolytica is a protozoan parasite responsible for amoebic dysentery and amoebiasis. It primarily infects the intestinal tract, causing symptoms like diarrhea, abdominal pain, and sometimes liver abscesses. The parasite has two forms: the infectious cyst and the trophozoite, which causes tissue damage. E. histolytica is transmitted through the fecal-oral route, often via contaminated water or food. Early diagnosis and treatment are crucial, as amoebiasis can lead to severe complications if untreated. Antiprotozoal medications such as metronidazole effectively treat infections caused by this pathogen.

Morphology

Entamoeba histolytica has two distinct forms: the cyst and the trophozoite. The cyst is spherical, measuring 10-20 micrometers, and contains four nuclei.

Cyst of Amoeba (Entamoeba histolytica) in saline wet mount of feces microscopic examination — Fig. Cyst of Amoeba (*Entamoeba histolytica*) in saline wet mount of feces microscopic examination

The trophozoite is the active, motile form, typically 12-60 micrometers in size.

Cyst of Entamoeba histolytica — Fig. Cyst of *Entamoeba histolytica* in iodine wet mount of feces

It has a single, central nucleus with a characteristic karyosome and a prominent pseudopod for movement. The trophozoite may also contain red blood cells, indicating its ability to invade tissue. Both forms are key to its transmission and pathogenesis.

Pathogenicity

Entamoeba histolytica is a protozoan parasite responsible for amoebiasis, which can cause intestinal dysentery and liver abscesses. The trophozoite form invades the intestinal mucosa, leading to ulceration and inflammation. This results in symptoms like abdominal pain, diarrhea, and sometimes bloody stools. In severe cases, the parasite can spread to other organs, including the liver, causing abscesses. Transmission occurs via the fecal-oral route, often through contaminated water or food. Cysts are the infectious stage and can survive in the environment. Left untreated, E. histolytica infections may lead to chronic disease or severe complications. Early detection and antiprotozoal treatment are essential to prevent long-term damage and spread.

Lab Diagnosis

The laboratory diagnosis of Entamoeba histolytica typically starts with microscopic examination of stool samples. The presence of trophozoites or cysts in the stool confirms infection. Cysts are round and contain up to four nuclei, while trophozoites have a single nucleus with a prominent karyosome. Wet mount preparations and iodine staining are commonly used for direct observation. Additionally, antigen detection tests, such as enzyme-linked immunosorbent assay (ELISA), can identify specific E. histolytica antigens in stool. PCR-based methods offer high sensitivity and specificity, helping differentiate E. histolytica from non-pathogenic amoebae.

Trophozoite of Entamoeba histolytica — Fig. Trophozoite of *Entamoeba histolytica* in LPCB preparation of stool

Serology may also be used, especially in cases with extraintestinal involvement, such as liver abscesses. Culture on special media like PEA (proteose peptone agar) can also be done, though it is less commonly used. Early diagnosis is crucial for effective treatment and to prevent complications.

Treatment

The treatment of Entamoeba histolytica infection typically involves antiprotozoal medications. Metronidazole is commonly used for intestinal amoebiasis and extraintestinal infections like liver abscesses. After initial treatment with metronidazole, paromomycin or iodoquinol may be used to clear intestinal cysts. In severe cases, surgical drainage may be required for liver abscesses. Additionally, supportive care, including rehydration, is essential to manage symptoms like diarrhea and dehydration. Early diagnosis and prompt treatment are critical to prevent complications and improve recovery outcomes.

Prevention

Prevention of Entamoeba histolytica infection primarily involves practicing good hygiene. First, always wash your hands with soap and water before eating or after using the restroom. Additionally, drinking clean, purified water is essential to avoid fecal contamination. Avoid eating raw or undercooked food, particularly in areas with poor sanitation. Proper disposal of human waste and the use of latrines can reduce environmental contamination. Moreover, travelers to endemic areas should consider antiprotozoal prophylaxis. Finally, education on sanitation practices is vital for communities at high risk of amoebiasis.

Keynotes

Entamoeba histolytica is a protozoan parasite responsible for amoebiasis, causing intestinal and extraintestinal infections.
It infects the intestinal tract, leading to dysentery, abdominal pain, and sometimes bloody diarrhea.
Cysts are the infectious form, transmitted via the fecal-oral route, commonly through contaminated food or water.
Trophozoites invade the intestinal mucosa, causing ulcers and potentially spreading to other organs, like the liver, leading to abscesses.
Microscopic examination of stool samples, along with antigen detection and PCR, aids in diagnosis.
Metronidazole is the primary treatment for intestinal and extraintestinal amoebiasis, often followed by paromomycin to clear cysts.
Prevention involves good sanitation, hygiene practices, and drinking clean water to reduce the risk of infection.
Early diagnosis and prompt treatment are essential to prevent severe complications and long-term health issues.

Related Footage

Entamoeba histolytica found during feces Microscopy @ 400X and 800X

Entamoeba histolytica(EH) Quadrinucleated Cyst in Iodine wet mount

Amoeba, trophozoites and cyst in LPCB preparation

Entamoeba histolytica-Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynote