## Core Concept
Rabies is a viral disease that affects the central nervous system (CNS) of mammals, including humans. The diagnosis of rabies involves a combination of clinical findings, laboratory tests, and epidemiological information. Laboratory confirmation is crucial for diagnosing rabies.

## Why the Correct Answer is Right
The correct answer, . (Presence of Negri bodies in the brain), is diagnostic of Rabies because Negri bodies are characteristic viral inclusions found in the neurons of animals infected with rabies. These inclusions are pathognomonic for rabies and can be identified through histopathological examination of brain tissue.

## Why Each Wrong Option is Incorrect
- **Option A:** (Presence of viral particles in stool) - This option is incorrect because the presence of viral particles in stool is not a diagnostic criterion for rabies. Rabies virus is typically identified in brain tissue or saliva.
- **Option B:** (Detection of rabies virus antigen in corneal smear) - Although this method can suggest rabies, it is not as definitive or commonly used as the detection of Negri bodies in brain tissue. Corneal smears can be used but are not the gold standard.
- **Option C:** (Isolation of virus in cell culture) - While isolation of the virus in cell culture is a confirmatory test for rabies, it is not listed as an option and takes time, making it less practical for immediate diagnosis compared to histopathological examination.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that the presence of Negri bodies in brain tissue is pathognomonic for rabies. However, it's worth noting that post-mortem diagnosis is often required for confirmation. In clinical practice, a high index of suspicion based on exposure history (e.g., animal bites) and symptoms like hydrophobia, aerophobia, and neurological deterioration leads to early treatment initiation.

## Correct Answer: D. Presence of Negri bodies in the brain.