Question

Infective stage of Entamoeba histolytica is
A. Trophozoite
B. Pre-cyst
C. Uninucleate cyst
D. Tetranucleate cyst

Answer 1

Hint: The life cycle of the Amoeba consists of three stages. These are trophozoite, pre-cystic and the cystic stage. The cysts that are eliminated in the faeces of the infected person are known as Tetranucleate. The infection with Entamoeba histolytica is acquired by the indirect faecal-oral route or through sexual intercourse. The water or food that is contaminated with the faeces is responsible for the entry of the cyst in healthy individuals. The infective stage in humans is this cyst.

Complete answer:
Option (A) is a trophozoite
Cysts and trophozoites of Entamoeba histolytica are passed in faeces. The cysts are typically found in the formed stool, whereas trophozoites are typically found in the diarrheal stool. The infection by Entamoeba histolytica occurs due to the ingestion of mature cysts in fecal contamination of food, water, or hands.

Option (B) pre cyst
In the precystic forms, entamoeba is found only in the intestinal lumen. There is variation in size of Entamoeba histolytica cysts. The cytoplasm of this is clear and at this stage each cyst is mononucleated. The characteristic of the cysts of Entamoeba histolytica is the presence of chromatoid bodies.

Option (C) is Uninucleate cyst
The life cycle of Entamoeba histolytica is 1. Cysts with 4 nuclei (it means metacysts) are orally ingested with the contaminated food or drinking water (A–C). 7 A uninucleated cyst (it means precyst) contains the chromatoid bodies and often a large glycogen vacuole. 8 Cysts with 2 nuclei and chromatoid bodies.

Option (D) is tetranucleate cyst
Tetranucleate cysts of Entamoeba and Giardia are the diagnostic and infectious stage of each parasite. The cyst wall, that is hard and impermeable to the small molecules, protects the Entamoeba and Giardia from the lysis due to environmental insults such as osmotic shock in the freshwater, stomach acid, and duodenal proteases.

Thus, the correct answer is an option D- Tetranucleate cyst.

Note:
Amebiasis is a disease which is caused by the parasite Entamoeba histolytica. It can affect anyone, but it is more common in people who live in tropical areas that have poor sanitary conditions.