Question

Arrange the following trematodes on the basis of their size starting from the smallest to the largest:
A. Fasciola hepatica
B. Heterophyes heterophyes
C. Opisthorchis tenuicollis
D. Notocotylus attenuates
E. Clonorchis sinensis
Choose the correct answer from the options given below:

• A. B, E, C, D, A
• B. D, C, B, A, E
• C. D, B, E, C, A
• D. B, D, C, E, A

Hint:

To easily remember sizes, associate the flukes with their micro-habitats: Heterophyes is a micro-intestinal fluke (smallest), Notocotylus is a small cecal fluke of birds, the liver flukes Opisthorchis and Clonorchis are medium-sized bile duct dwellers, and Fasciola hepatica is a large fluke occupying major bile ducts.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Trematodes exhibit highly variable morphology and dimensions depending on their species, family, and target organ in the host.
Identifying adult flukes based on physical length is crucial for post-mortem diagnosis.
Ranking these parasites from smallest to largest requires a comparison of their typical adult body lengths.

Step 2: Detailed Explanation:
Let us review the standard adult dimensions of each of the given flukes:
1. Heterophyes heterophyes (B):
This is an extremely small intestinal fluke of fish-eating mammals and birds.
Its adult length ranges from only $1.0\text{ mm}$ to $1.7\text{ mm}$.
This makes it the smallest fluke in the list.
2. Notocotylus attenuates (D):
This is an intestinal and cecal fluke of waterfowl and poultry.
Its adult body is relatively small, measuring approximately $2.0\text{ mm}$ to $5.0\text{ mm}$ in length.
3. Opisthorchis tenuicollis (C):
This is a cat liver fluke residing in the bile ducts.
The adult worm measures about $7.0\text{ mm}$ to $12.0\text{ mm}$ in length.
4. Clonorchis sinensis (E):
The Chinese liver fluke resides in the bile ducts of humans and other fish-eating mammals.
Its adult stage is slightly larger than Opisthorchis, measuring approximately $10.0\text{ mm}$ to $25\text{ mm}$ in length.
5. Fasciola hepatica (A):
The common liver fluke is a large, leaf-shaped parasite of ruminants.
The adult flukes are quite large, measuring about $20.0\text{ mm}$ to $0\text{ mm}$ in length and up to $13.0\text{ mm}$ in width.
This is the largest trematode among the given choices.
Arranging these species from smallest to largest based on adult length gives:
Heterophyes heterophyes (B) $\rightarrow$ Notocotylus attenuates (D) $\rightarrow$ Opisthorchis tenuicollis (C) $\rightarrow$ Clonorchis sinensis (E) $\rightarrow$ Fasciola hepatica (A).
This corresponds to the sequence: B, D, C, E, A.

Step 3: Final Answer:
The correct sequential arrangement from smallest to largest is B, D, C, E, A.
Therefore, the correct answer is option (D).