INTESTINAL – ENTAMOEBA HISTOLYTICA
Q.1: Describe the morphology of Entamoeba histolytica
- Entamoeba histolytica is a protozoan parasite belonging to the genus Entamoeba.
- It is a large, oval-shaped organism, measuring 20-60 μm in diameter.
- The trophozoite form has a distinct nucleus with a large karyosome, and a clear cytoplasm with a characteristic 'halo' around the nucleus.
- The cyst form is smaller, measuring 10-15 μm in diameter, and has a double layer of cyst walls.
Q.2: Describe the life cycle of Entamoeba histolytica
- Ingestion: The parasite is ingested through contaminated food or water.
- Excystation: The cyst form is digested in the small intestine, releasing four trophozoites.
- Trophozoite stage: The trophozoites attach to the intestinal mucosa, feed on host cells, and multiply.
- Cyst formation: The trophozoites develop into cysts, which are passed out in the feces.
- Transmission: The cysts are ingested by a new host, and the cycle repeats.
Memory trick: "ICE TROPHOZOITE CUBES" – Ingestion, Excystation, Trophozoite, Cyst formation, and Transmission.
Q.3: Describe the clinical manifestations of Entamoeba histolytica
- Dysentery: bloody diarrhea, abdominal pain, and fever.
- Amoebic liver abscess: right upper quadrant pain, fever, and jaundice.
- Intestinal obstruction: abdominal pain, vomiting, and constipation.
- Extraintestinal amoebiasis: abscesses in the lungs, liver, or other organs.
Q.4: Enumerate the differences between Amoebic dysentery and Bacillary dysentery
| Characteristic | Amoebic Dysentery | Bacillary Dysentery |
|---|---|---|
| Causative agent | Entamoeba histolytica | Shigella spp. |
| Presence of blood | Yes | No |
| Mucus in stool | Yes | No |
| Abdominal pain | Yes | Yes |
| Fever | Yes | Yes |
| Duration of illness | 7-14 days | 1-7 days |
Q.5: Describe the laboratory diagnosis of amoebiasis
- Stool examination: cysts and trophozoites can be identified.
- Serological tests: ELISA and IFA can detect antibodies against E. histolytica.
- Imaging studies: CT or ultrasound can detect liver abscesses.
- Endoscopy: biopsy can be taken for histopathological examination.
Memory trick: "STEPS" – Stool examination, Serological tests, Imaging studies, and Endoscopy.