**Question:** A 15 year old girl was admitted to the infectious disease hospital with a provisional diagnosis of rabies. The most suitable clinical sample that can confirm the ante mortem diagnosis is-

A. Brain tissue
B. Blood
C. Saliva
D. Skin biopsy

**Correct Answer:** A. Brain tissue

**Core Concept:**
Rabies is a fatal viral infection of the central nervous system caused by the Rhabdoviridae family, specifically the Lyssavirus genus. In humans, the virus primarily affects the brain and central nervous system. The diagnosis of rabies is crucial to initiate timely treatment and prevent the disease progression.

**Why the Correct Answer is Right:**
Brain tissue is the most suitable clinical sample for ante mortem confirmation of rabies diagnosis because:

1. High Viral Load: Rabies virus has a high viral load in the brain, making it the most likely site for viral detection.
2. Direct Sample: Brain tissue samples can directly detect the presence of rabies virus and confirm the diagnosis.
3. Early Diagnosis: Collecting brain tissue samples allows for ante mortem diagnosis, enabling prompt treatment and preventing further disease progression.

**Why Each Wrong Option is Incorrect:**

A. **Brain tissue**: Although brain tissue is essential for postmortem diagnosis, it is not suitable for ante mortem diagnosis due to ethical concerns and the need to prevent patient deterioration.
B. **Blood**: While rabies virus can be detected in blood, the viral load is much lower compared to brain tissue, making it less reliable for ante mortem diagnosis.
C. **Saliva**: Rabies virus can be detected in saliva, but the viral load is generally low, posing challenges in obtaining a definitive diagnosis with a single saliva sample. Moreover, saliva samples may not always be available in the early stages of the disease when the diagnosis is crucial.
D. **Skin biopsy**: Skin biopsies may not reveal the presence of rabies virus, as the virus primarily affects the central nervous system, not skin.

**Clinical Pearl:**

To make a definitive diagnosis of rabies, it is essential to focus on collecting samples from the affected central nervous system, specifically brain tissue, during the early stages of the disease. This ensures the highest viral load and allows for ante mortem diagnosis, enabling prompt treatment and potentially saving the patient's life.