Question

Assertion (A): Elephantiasis is due to the obstruction of lymphatic vessels by accumulation of dead filarial worms.
Reason (R): First stage microfilaria larva is the infective stage to humans.

• A. Both (A) and (R) are true. (R) is correct explanation for (A)
• B. Both (A) and (R) are true. (R) is not correct explanation for (A)
• C. (A) is true. But (R) is false
• D. (A) is false. But (R) is true

Hint:

The vector for Wuchereria bancrofti is the female Culex mosquito.
The infective stage for humans is always the third-stage (L3) filariform larva.

Answer 1

The Correct Option is C

Step 1: Look at the assertion on its own.
Elephantiasis is a swelling disease and the question asks whether dead adult worms blocking lymph vessels explain it.
Step 2: Confirm the assertion using the filarial life cycle.
Adult Wuchereria bancrofti worms live for years in lymph vessels and nodes, and when they die they trigger inflammation and fibrosis that blocks lymph flow, causing the characteristic swelling, so the assertion is true.
Step 3: Check the reason about the infective stage.
It is not the first stage microfilaria that infects humans, the infective stage delivered by the mosquito bite is the third stage filariform larva, so the reason as stated is false.
Final answer: Option 3, assertion true but reason false.