Author:

Herbert NeilWigder

Signs and Symptoms

• Once a patient exhibits clinical signs, the course is almost universally fatal
• 5 stages: Incubation, prodrome, acute neurologic signs, coma, death (or recovery):
  • Incubation: Days to years (average 1-2 mo):
    • Virus amplifies in peripheral tissues and travels to the CNS
    • Time depends on amount inoculated and proximity to CNS, thus shorter incubation for kids and adults with bites close to the CNS
  • Prodrome: 1-10 d:
    • Nonspecific symptoms: Fever, headache, malaise, myalgias, anorexia, sore throat, nausea, and vomiting
    • Paresthesias, pain, or fasciculations around bite site give clue to diagnosis
  • Acute neurologic signs (classic form): 2-7 d:
    • Anxiety, agitation, hallucinations, confusion or delirium, muscle spasms, opisthotonos, and seizure
    • Aerophobia (pathognomonic): Pharyngeal spasm from draft of air
    • Hydrophobia (pathognomonic): Violent involuntary muscle contraction of diaphragm, pharyngeal, laryngeal, and accessory respiratory muscles when attempting to swallow (seen in up to half of cases)
    • Dysrhythmias, myocarditis, autonomic instability, and fevers
    • Brainstem involvement: Diplopia, facial paralysis
  • Coma:
    • Apnea from respiratory center involvement, vascular collapse, flaccid paralysis, adult respiratory distress syndrome, syndrome of inappropriate diuretic hormone
  • Death (or recovery):
    • Most die within 2 wk of symptoms
    • Rare case reports of survival
    • Known survivors have some residual neurologic deficits
• 3 manifestations of disease:
  • Classic or encephalitic rabies accounts for ∼80% of cases. See above
  • Paralytic rabies (∼20%): Ascending paralysis mimicking Guillain-Barre syndrome (GBS)
  • Atypical rabies (<1%): Characterized by neuropathic pain, sensory or motor deficits, choreiform movements, myoclonus, and seizures

Essential Workup

Several tests are used to diagnose rabies in humans, but no single test is sufficient

Diagnostic Tests & Interpretation

Differential Diagnosis

• Rabies exposure:
  • Nonmammal bites including bird and snake bites
• Rabies:
  • Other causes of encephalitis:
    • Herpesviruses: HSV1, VZV
    • Enterovirus (Coxsackie, echovirus, poliovirus)
    • Arboviruses (West Nile, Eastern/Western equine encephalitis, St. Louis)
  • Tetanus
  • Delirium tremens
  • Psychosis/tox
  • GBS
  • Polio
  • Tick-bite paralysis
  • Immune-mediated polyneuritis
  • Botulism

Prehospital

• Thoroughly wash wound with soap and water
• If safely able, capture animal for observation or sacrifice and testing

Initial Stabilization/Therapy

• ATLS for stabilization of any trauma secondary to the bite
• Wound care:
  • Flush the wound with soap and water for 15 min
  • If available, a virucidal agent should be used (e.g., povidone-iodine)

ED Treatment/Procedures

• Determine if postexposure prophylaxis (PEP) is required: Rabies exposure is a medical urgency not emergency. When in doubt, consult with local or state health officials for recommendations:
  • Domestic animal bite (dogs, cats, and ferrets):
    • Home monitoring of animal for 10 d
    • If animal displays no signs of illness, patient does not need PEP
    • If animal displays signs of rabies, initiate PEP
  • Wild animal bite (raccoons, skunks, foxes, most other carnivores, bats):
    • Rabies testing of sacrificed animal
    • Start PEP immediately and stop if test is negative
    • Treat if animal not captured
  • Livestock, horses, rodents, rabbits, other mammal bites, and mammal bites outside of the U.S.:
    • Consult public health official for recommendation
• PEP:
  • Passive immunization with human rabies immune globulin (HRIG)
    • HRIG: 20 U/kg: Majority infiltrated in and around wound. Remainder given IM distant from the vaccine
  • Active immunization with rabies vaccine:
    • Rabies vaccine: 1 mL IM days 0, 3, 7, 14, add day 28 if immunocompromised
    • Administration location: Deltoid in adults, anterolateral thigh in small children and infants
  • Those with pre-exposure prophylaxis and rabies exposure:
    • Do not require HRIG
    • Need vaccine booster on days 0 and 3
  • If care delayed after rabies exposure:
    • Vaccine should be administered as usual
    • If not available at time of the first vaccine, HRIG can be administered up to 7 d after the administration of the first dose of vaccine
• Pre-exposure prophylaxis:
  • Rabies vaccine on days 0, 7, and 21 or 28
  • Target groups: Veterinarians, animal hand lers, virus lab workers, foreign travelers in endemic regions
• Make sure tetanus immunization is updated
• Prophylactic antibiotics to prevent wound infection if indicated

Disposition

Ensure adequate access for subsequent vaccine administration post rabies exposure

Follow-up Recommendations

• Ensure access to subsequent vaccine doses
• Patient should follow up with animal control if source animal has been sacrificed or is being observed

• American Academy of Pediatrics. Red Book 2018-2021. Report of the Committee on Infectious Diseases. 31st ed.Itasca, IL: American Academy of Pediatrics; 2018.
• Centers for Disease Control and Prevention. Rabies . Available at http://www.cdc.gov/rabies/index.html.
• Centers for Disease Control and Prevention. Use of a reduced (4-dose) vaccine schedule for postexposure prophylaxis to prevent human rabies: Recommendations of the advisory committee on immunization practices . MMWR. 2010;59(No. RR-2):1-8.
• CrowcroftNS, ThampiN. The prevention and management of rabies . BMJ. 2015;350:g7827.
• FooksAR, BanyardAC, HortonDL, et al. Current status of rabies and prospects for elimination . Lancet. 2014;384:1389-1399.
• World Health Organization. Rabies fact sheet . http://www.who.int/mediacentre/factsheets/fs099/en/. Updated September 2017.

See Also (Topic, Algorithm, Electronic Media Element)

• Encephalitis
• Meningitis

ICD9

• 071 Rabies

• V01.5 Contact with or exposure to rabies

ICD10

• A82.9 Rabies, unspecified

• Z20.3 Contact with and (suspected) exposure to rabies

SNOMED

• 14168008 Rabies (disorder)

• 444459008 Exposure to Rabies virus (event)

• 266196000 Rabies - hydrophobia (disorder)