Negri bodies are characteristic of: September 2008, March 2013
**Core Concept**
Negri bodies are eosinophilic, spherical inclusions found within the cytoplasm of infected neurons. They are a hallmark of rabies virus infection.
**Why the Correct Answer is Right**
Negri bodies are formed when the rabies virus replicates within the neurons, causing the formation of viral nucleocapsids that accumulate within the cytoplasm. These viral inclusions are a result of the viral RNA being encapsidated by the nucleocapsid protein, which is then visualized as Negri bodies under light microscopy. The presence of Negri bodies in infected neurons is a diagnostic feature of rabies, a fatal viral encephalitis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Negri bodies are not associated with herpes simplex virus infection, which typically causes vesicular skin lesions and encephalitis.
**Option B:** This option is incorrect because Cowdry type A inclusions are characteristic of herpes simplex virus infection, not rabies.
**Option C:** This option is incorrect because Cowdry type B inclusions are characteristic of cytomegalovirus infection, not rabies.
**Option D:** This option is incorrect because intranuclear inclusions are characteristic of various viral infections, such as cytomegalovirus and herpes simplex virus, but not rabies.
**Clinical Pearl / High-Yield Fact**
To remember the key features of rabies, recall the "Furious Dog" mnemonic: "F - Furious animal behavior, O - Onset is sudden, U - Unusual fear of water (hydrophobia), R - Respiratory failure, I - Inflammation of the brain (encephalitis), O - Often fatal, U - Unresponsive, S - Spinal cord involvement, D - Death."
**Correct Answer:** C.