Epidemiology


Etiology


  • Pathogen
    • Rabies is caused by several different members of the Rhabdoviridae family.
    • Rhabdoviruses are rod or bullet shaped
    • Genus: Lyssavirus
    • ssRNA
  • Transmission
    • Most common animal reservoir worldwide: dogs
    • Most common animal reservoirs in the US: bats, raccoons, skunks, and foxes
    • Spread through saliva of rabid animal after bite injury
    • Via aerosols (e.g., bat caves); rare

Pathophysiology


Rabies virus binds the ACh receptor of peripheral nerves in the bite wound → migrates retrogradely along the axonal microtubules (using motor protein dynein) → enters the CNS → infects the brain

Clinical features


Encephalitic rabies (most common type)

  • Hydrophobia: Rabies patients experience involuntary, painful pharyngeal muscle spasms when trying to drink; later on in the disease, the sight of water alone may provoke nausea or vomiting.
  • CNS symptoms
    • Anxiety, agitation, and combativeness alternating with calm periods
    • Confusion and hallucinations
    • Photophobia
    • Fasciculations
    • Seizures
    • ↑ Muscle tone and reflexes with nuchal rigidity
  • Autonomic symptoms (e.g., hypersalivation, hyperhidrosis)
  • Coma and death within days to weeks of the development of neurological symptoms

Paralytic rabies (< 20% of cases)

  • Flaccid paralysis, gradually ascending and spreading from bite wound
  • Paraplegia and loss of sphincter tone
  • Respiratory failure and death

Diagnostics


  • Postmortem brain tissue autopsy
    • Histopathological findings: Negri bodies (eosinophilic cytoplasmic inclusion bodies typically found in the cerebellum and hippocampus)

Treatment