NEET-PG 2018 — Microbiology

22 Questions — Page 3 of 3

Q21

The life cycle shown in the image below is characteristic of which organism?

Q22

Which of the following Schistosoma egg is shown below?

NEET-PG 2018 - Microbiology NEET-PG Practice Questions and MCQs

Question 21: The life cycle shown in the image below is characteristic of which organism?

A. Schistosomiasis (Correct Answer)
B. Paragonimus
C. Fasciolopsis buski
D. Fasciola hepatica

Explanation: ***Schistosomiasis*** - The image clearly depicts the characteristic **cercariae** penetrating human skin, with subsequent migration to the portal blood and maturation into adult worms in specific venous plexuses (e.g., rectum, liver, bladder). - The presence of **miracidia** hatching from eggs and infecting snails, followed by the release of cercariae from snails, is the hallmark life cycle of *Schistosoma* species. The eggs are shown in feces and urine, indicating different species of Schistosoma. *Paragonimus* - The life cycle of *Paragonimus* (lung flukes) involves ingestion of **undercooked crustaceans** (crabs or crayfish) containing metacercariae, not skin penetration by cercariae. - Adult worms typically reside in the **lungs**, and eggs are coughed up and swallowed or passed in feces, which is different from the venous system involvement shown. *Fasciolopsis buski* - *Fasciolopsis buski* (intestinal fluke) infection occurs through ingestion of **aquatic plants** contaminated with metacercariae. - The adult worms reside in the **small intestine**, and while eggs are passed in feces, the characteristic skin penetration by cercariae is absent in its life cycle. *Fasciola hepatica* - *Fasciola hepatica* (liver fluke) is acquired by ingesting **metacercariae** on aquatic vegetation, similar to *Fasciolopsis buski*. - Adult worms inhabit the **bile ducts** of the liver, and the life cycle does not involve skin penetration by cercariae as the mode of human infection.

Question 22: Which of the following Schistosoma egg is shown below?

A. Schistosoma mansoni
B. Schistosoma hematobium (Correct Answer)
C. Schistosoma japonicum
D. Cannot be differentiated on wet mount

Explanation: ***Schistosoma hematobium*** - The image clearly displays an **elongated, oval-shaped egg** with a characteristic **terminal spine**. - This morphology is pathognomonic for **Schistosoma hematobium**, distinguishing it from other Schistosoma species. *Schistosoma mansoni* - Eggs of *Schistosoma mansoni* are typically **oval-shaped** with a distinct **lateral spine**. - The spine is located on the side of the egg, not at one of its poles as seen in the image. *Schistosoma japonicum* - *Schistosoma japonicum* eggs are more **rounded or oval** and possess a very small, **rudimentary spine** that is often difficult to visualize or absent. - The clearly visible, prominent terminal spine in the image rules out *S. japonicum*. *Cannot be differentiated on wet mount* - The distinct morphological features (shape and spine location) of Schistosoma eggs allow for reliable differentiation on a **wet mount** microscopic examination. - These features are crucial for accurate species identification in laboratory diagnostics.