USMLE

Rhabdovirus

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Viruses - RNA Viruses
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Summary

Rhabdoviruses are a class of RNA viruses that contain negative-sense RNA. They utilize a helical capsid, and are further surrounded by a viral envelope.

The most common rhabdovirus is rabies, which is a bullet shaped virus that is transmitted through bats and other wild animals like racoons. Rabies binds to neuronal nicotinic acetylcholine receptors in the peripheral nervous system, and travel in a retrograde fashion back to reach the brain or central nervous system. A rabies infection that reaches the brain causes encephalitis, which manifests clinically as hypersalivation, photophobia, and hydrophobia. To diagnose a rabies infection, clinicians do a brain biopsy and then search brain tissue for intracellular inclusions called Negri bodies. It is crucial that a patient who may be exposed to a rabid animal receive a killed rabies vaccine and rabies immunoglobulin as soon as possible to prevent the spread of the virus to the brain.

Key Points

  • Rhabdoviruses
    • Characteristics
      • RNA viruses
        • replicate in the cytoplasm of cells
        • Single-stranded
        • - sense
          • Must be translated into +RNA for translation and replication
        • Linear genome
      • Enveloped
      • Helical capsid
    • Presentation
      • Rabies virus
        • Characteristics
          • Bullet-shaped virus
        • Transmission
          • bat, raccoon, and skunk bites
            • More common than dog bites in US
          • Aerosol transmission (bat caves) also possible
        • Pathophysiology and Presentation: Rabies
          • Long incubation period (weeks to months) before symptom onset
          • Binds to ACh receptors
            • Travels to CNS by migrating in retrograde fashion (via dynein motors) up nerve axons
          • Prodrome (Fever, malaise, pharyngitis, pain around bite site)
          • Encephalitis
            • hypersalivation
            • photophobia
            • hydrophobia
            • paralysis
            • agitation, coma, focal neurological deficits, death
        • Diagnosis
          • Brain Biopsy
            • Usually diagnosed post-mortem
            • Negri bodies
              • Round eosinophilic cytoplasmic inclusions found in
                • Purkinje cells of cerebellum
                • pyramidal hippocampal neurons
          • RT-PCR can also be used
        • Post-exposure Prophylaxis
          • Wound cleaning
          • Killed (inactivated) vaccine
            • Active immunization
          • Rabies immunoglobulin
            • Passive immunization
        • Treatment
          • Supportive