A child from Bihar comes with fever. Blood examination shows sheathed microfilaria with 2 nuclei in tail tip. The diagnosis is
**Core Concept**
The question tests the ability to diagnose a specific type of filariasis based on the morphological characteristics of microfilariae. **Microfilariae** are the larval stages of filarial parasites that can be found in the bloodstream. Bihar is an endemic region for certain types of filariasis.
**Why the Correct Answer is Right**
Given the description of sheathed microfilaria with 2 nuclei in the tail tip, this is characteristic of **Wuchereria bancrofti**, the causative agent of lymphatic filariasis. The presence of a sheath and the specific nuclear pattern in the tail are key identifying features.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not match the description provided.
**Option B:** Incorrect as it does not correspond with the given characteristics.
**Option D:** Incorrect because the description does not fit this option.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that **Wuchereria bancrofti** is the most common cause of lymphatic filariasis, which can lead to significant morbidity, including elephantiasis. The microfilarial periodicity (nocturnal periodicity) is also an important aspect of its diagnosis.
**Correct Answer:** D. Wuchereria bancrofti