Rabies | Anatomy2Medicine
Rabies Causes

Rabies

    • Rhabdoviruses
      • enveloped, bullet-shaped viruses (MCQ)
      • Each contains a helical nucleocapsid
      • into two genera:
        • Lyssavirus – rabies virus, (MCQ)
        • Vesiculovirus – vesicular stomatitis virus (VSV),
  • Rabies virus
      • raccoons, skunks, squirrels, foxes, and bats, , domestic dogs and cats provide reservoirs
      • Humans are usually infected by the bite of an animal,
      • The genomic negative-strand RNA is nonsegmented(MCQ)
  • Pathology
        • Following inoculation, the virus may replicate locally
        • travels via retrograde transport within peripheral neurons to the brain
        • it replicates primarily in the gray matter  of the brain (MCQ)
        • From the brain, the rabies virus can travel along autonomic nerves
        • It leads to infection of the lungs, kidney, adrenal medulla, and salivary glands. (MCQ)
        • Contamination of saliva potentially leads to further transmission of the disease
        • The extremely variable incubation period depends on the (MCQ)
          • host’s resistance
          • amount of virus transferred
          • distance of the site of initial infection from the CNS
        • Incubation generally lasts 1 to 8 weeks
      • Clinical illness
        • begin with an abnormal sensation at the site of the bite
        • progress to a fatal encephalitis (MCQ)
        • neuronal degeneration of the brain and spinal cord occur
      • Symptoms include
  • hallucinations; seizures
  • weakness; mental dysfunction
        • paralysis; coma; and, finally, death.
        • classic rabid sign of hydrophobia (MCQ)
          • Shown by many, but not all, patients
          • hydrophobia” refers to the infected individual’s painful inability to swallow liquids (due to pharyngeal spasms), leading to avoidance.
  • Laboratory identification
  • Negri bodies (MCQ)
          • characteristic eosinophilic cytoplasmic inclusions
          • identified in certain regions of the brain such as the hippocampus (MCQ)
          • diagnostic of rabies
        • Prior to death, the diagnosis can be made by
          • identification of viral antigens in biopsies of
            • skin from the back of the neck
            • from corneal cells (MCQ)
          • by demonstration of the viral nucleic acid by reverse transcription poly- merase chain reaction (RT-PCR) in infected saliva (MCQ)
  • Treatment and prevention
      • A killed rabies virus vaccine is available for prophylaxis
      • two vaccine formulations are approved by FDA
        • Both contain inactivated virus grown in cultured cells (chick embryo cells or human diploid cells). (MCQ)
  • Preexposure prophylaxis
      • indicated for individuals at high risk because of the work they do (for example, for veterinarians).
    • Postexposure prophylaxis
      • treatment instituted after an animal bite or exposure to an animal (or human) suspected of being rabid
      • consists of
        • thorough cleaning of the wound
        • passive immunization with antirabies immunoglobulin(MCQ)
        • active immunization with the rabies vaccine (HDCV, the human diploid cell vaccine). (MCQ)