**Core Concept:** Japanese Encephalitis (JE) is a viral infection caused by the Japanese Encephalitis Virus (JEV) and is primarily transmitted to humans through the bite of an infected mosquito. JE infection can lead to severe neurological complications, including encephalitis and death.

**Why the Correct Answer is Right:**

Japanese Encephalitis is primarily transmitted to humans through the bite of infected mosquitoes, particularly the Culex mosquito species. The correct answer (D) highlights that the question is asking about an aspect of the disease that is NOT transmitted through a vector other than mosquitoes. In reality, JE is primarily transmitted via infected mosquitoes, not through any other means.

**Why Each Wrong Option is Incorrect:**

A. This option discusses the mode of transmission, which is incorrect because the infection is primarily transmitted through mosquitoes.
B. This option mentions the occurrence of the disease in humans, which is true but does not address the main mode of transmission, which is the focus of the question.
C. This option talks about the severity of the disease, which is true but does not address the specific mode of transmission under discussion.

**Clinical Pearl / High-Yield Fact:** Japanese Encephalitis is a significant public health concern in Asia, particularly in countries like India, Bangladesh, and parts of China. Mosquito control measures and vaccination are essential preventive strategies against JE.

**Correct Answer:** D. The disease is NOT transmitted through contact with infected pigs or horses, which are incorrect modes of transmission for Japanese Encephalitis. Japanese Encephalitis primarily occurs due to mosquito bites, making option D the correct answer.