**Core Concept**
Tropical pulmonary eosinophilia (TPE) is a rare, severe form of allergic reaction to filarial parasites, primarily Wuchereria bancrofti. It is characterized by an intense eosinophilic response in the lungs, leading to pulmonary symptoms and signs.

**Why the Correct Answer is Right**
Tropical pulmonary eosinophilia is a clinical diagnosis that occurs in the absence of microfilariae in the peripheral blood. The intense eosinophilic response is a hallmark of this condition, and microfilariae are typically absent from the blood due to the body's immune response. This absence of microfilariae in the blood is a key feature that distinguishes TPE from other forms of filariasis.

**Why Each Wrong Option is Incorrect**
**Option A:** Eosinophilia >3000/mm3 is a characteristic feature of tropical pulmonary eosinophilia, which is why this option is incorrect.
**Option C:** Paroxysmal cough and wheeze are typical pulmonary symptoms of TPE, making this option incorrect.
**Option D:** Bilateral chest mottling and increased bronchovascular markings are radiographic features of TPE, which is why this option is also incorrect.

**Clinical Pearl / High-Yield Fact**
Tropical pulmonary eosinophilia is often associated with a strong IgE response to filarial antigens, which can lead to severe pulmonary symptoms. The absence of microfilariae in the blood is a key diagnostic clue, and a high index of suspicion is required to diagnose this condition.

**Correct Answer Line**
✓ Correct Answer: B. Microfilaria in blood