Question

Select the correct sequence of Schistosoma nasale life cycle
A. Redia
B. Cercaria
C. Miracidium
D. Sporocyst
E. Metacercaria
Choose the correct answer from the options given below:

• A. C \(\rightarrow\) D \(\rightarrow\) A \(\rightarrow\) E
• B. C \(\rightarrow\) D \(\rightarrow\) B
• C. C \(\rightarrow\) A \(\rightarrow\) D \(\rightarrow\) E
• D. C \(\rightarrow\) B \(\rightarrow\) E

Hint:

Schistosome Life Cycle Exception: Unlike Fasciola (Miracidium $\rightarrow$ Sporocyst $\rightarrow$ Redia $\rightarrow$ Cercaria $\rightarrow$ Metacercaria), Schistosoma has NO REDIA and NO METACERCARIA: Miracidium (C) $\rightarrow$ Sporocyst (D) $\rightarrow$ Cercaria (B).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Schistosome (blood fluke) developmental life cycles lack redial and metacercarial stages, proceeding directly from miracidium to two generations of sporocysts and fork-tailed cercariae.
Key Formula or Approach:
\[ \text{Schistosome Life Cycle: } \text{Egg} \rightarrow \text{Miracidium (C)} \rightarrow \text{Mother \& Daughter Sporocysts (D)} \rightarrow \text{Furcocercous Cercaria (B)} \]

Step 2: Detailed Explanation:
Developmental stages in the life cycle of {Schistosoma nasale (Nasal Schistosomiasis Snoring Disease of cattle):
1. Miracidium (C): Hatches from the characteristic boomerang-shaped egg in water and penetrates the intermediate snail host (Indoplanorbis exustus).
2. Sporocyst (D): Transforms in snail tissues into mother sporocysts, which produce daughter sporocysts.
3. Cercaria (B): Daughter sporocysts directly give rise to free-swimming, fork-tailed furcocercous cercariae that emerge from the snail and actively penetrate host nasal mucosa/skin.
(Schistosomes completely lack redia and encysted metacercaria stages).
Sequence: C $\rightarrow$ D $\rightarrow$ B.

Step 3: Final Answer:
Hence, the correct life cycle sequence is C $\rightarrow$ D $\rightarrow$ B, matching option (B).