Diagnostic virology: Negri bodies are characteristic intracytoplasmic inclusions observed in neurons infected by which virus?

Introduction / Context:
Histopathological inclusion bodies are classic diagnostic clues in virology. Negri bodies are among the most well-known, historically used to confirm a lethal zoonotic infection.

Given Data / Assumptions:

• Negri bodies are eosinophilic intracytoplasmic inclusions in neurons.
• Question asks which virus produces them.

Concept / Approach:
Negri bodies are pathognomonic for rabies virus infection (Rhabdoviridae). They are found particularly in hippocampal pyramidal cells and Purkinje cells of the cerebellum and represent sites of viral replication and nucleocapsid accumulation.

Step-by-Step Solution:
Identify inclusion type: Negri bodies in neuronal cytoplasm. Associate with etiologic agent: rabies virus. Exclude other poxviruses and paramyxoviruses that have different inclusion patterns. Select rabies virus.

Verification / Alternative check:
Immunofluorescence or RT-PCR for rabies virus in brain tissue corroborates histologic findings; animal models show identical inclusions.

Why Other Options Are Wrong:

• Paramyxoviruses: can form syncytia and inclusions but not classic Negri bodies.
• Vaccinia and fowlpox: poxviruses replicate in cytoplasm with different inclusion types.

Common Pitfalls:
Confusing general inclusion bodies with Negri bodies; exact morphology and location matter.

Final Answer:
Rabies virus