**Core Concept**
Japanese encephalitis (JE) is a mosquito-borne viral disease that follows a **bird–mosquito–human transmission cycle**, where birds act as reservoir hosts, mosquitoes (primarily *Culex* species) serve as vectors, and humans are accidental hosts.

**Why the Correct Answer is Right**
JE virus is transmitted through the **bird–mosquito–human** chain. Birds (especially waterfowl) maintain the virus in nature, mosquitoes become infected by biting infected birds and then transmit the virus to humans via bites. Humans do not play a role in virus amplification; they are dead-end hosts. This makes JE a classic example of a disease with a **zoonotic and arthropod-mediated transmission cycle** involving birds and mosquitoes.

**Why Each Wrong Option is Incorrect**
Option A: Malaria is transmitted by *Anopheles* mosquitoes, with **human–mosquito–human** cycle, no involvement of birds.
Option C: Paragonimus is a **parasitic trematode** transmitted via **intermediate host (crustacean or snail) → human**, not involving birds or arthropods in the chain.
Option D: Plague is transmitted by **rodents → fleas → humans**, involving mammals and arthropods, but **no bird component**.

**Clinical Pearl / High-Yield Fact**
Remember: **"Bird–mosquito–human"** is the hallmark of Japanese encephalitis. It is endemic in Asia and occurs in rice paddies and areas with high bird density. Vaccination and mosquito control are key preventive measures.

✓ Correct Answer: B. Japanese encephalitis