Rabies

Definition

is an acute, progressive, almost universally fatal viral encephalitis caused by Rabies lyssavirus (family Rhabdoviridae). Transmission occurs primarily through the saliva of infected mammals via bites, scratches, or mucosal exposure. Once clinical symptoms appear, rabies is nearly 100% fatal, making prevention and post-exposure prophylaxis (PEP) critical. Virology & Pathophysiology

  • Enveloped, negative-sense single-stranded RNA virus
  • Replicates initially in muscle tissue at the exposure site
  • Enters peripheral nerves via nicotinic acetylcholine receptors
  • Travels retrograde to the central nervous system
  • Causes fatal encephalitis and autonomic dysfunction

Epidemiology (Key Clinical Context)

  • Endemic worldwide; highest burden in Asia and Africa
  • In Canada/US: most human cases linked to bats, followed by raccoons, skunks, and foxes
  • Dogs remain the primary global reservoir

Clinical Presentation Incubation period: typically 1–3 months (range: days to years) Prodromal phase

  • Fever, malaise, headache
  • Paresthesia or pain at bite site (classic early sign)

Neurologic phase

  • Encephalitis, agitation, confusion
  • Hydrophobia, aerophobia
  • Hypersalivation
  • Seizures, autonomic instability

Paralytic rabies (less common)

  • Ascending flaccid paralysis mimicking Guillain–Barré

Diagnosis

  • Primarily clinical
  • Confirmatory tests (often post-mortem):
    • RT-PCR (saliva, CSF)
    • Direct fluorescent antibody test (skin biopsy)
  • Do not delay PEP while awaiting confirmation

Pharmacist’s Role & Clinical Pearls Post-Exposure Prophylaxis (PEP) PEP is 100% effective if administered promptly and correctly before symptom onset. Components:

  1. Immediate wound cleansing
    • Soap and water ≥15 minutes
    • Virucidal agents (e.g., povidone-iodine)
  2. Rabies Immune Globulin (RIG)
    • 20 IU/kg (human RIG)
    • Infiltrate as much as possible around wound
    • Remaining volume IM (not in same site as vaccine)
    • Give once only, preferably day 0
  3. Rabies Vaccine (HDCV or PCECV)
    • IM in deltoid (anterolateral thigh in infants)
    • Unvaccinated: days 0, 3, 7, 14
    • Previously vaccinated: days 0 and 3 only (no RIG)

Pre-Exposure Prophylaxis (PrEP) Indicated for:

  • Veterinarians
  • Laboratory workers
  • Wildlife handlers
  • Travelers to high-risk endemic areas

Schedule: days 0 and 7 (IM) Key Drug Safety & Practice Points

  • Never inject vaccine into gluteal muscle (↓ immunogenicity)
  • RIG should never exceed recommended dose
  • Avoid corticosteroids unless clinically necessary
  • Pregnancy is not a contraindication to PEP
  • Immunocompromised patients require serologic confirmation of response
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