Rabies

Aka: Rabies, Rabies Encephalitis, St Hubert's Disease, Lyssa Virus Infection, Hydrophobia

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II. Epidemiology

  1. Worldwide: Responsible for 59,000 deaths worldwide per year (95% in Asia and Africa)
    1. Children under age 15 years account for 40% of cases
  2. U.S.
    1. Typically 1-3 Rabies (up to 8 in some years) cases in U.S. per year
    2. Most cases of Rabies are from exposure to wild animals in U.S. (90%)
    3. Up to 8000/year in U.S. of documented cases of Rabies in animals
      1. The most common reported domestic Rabies cases are in cats
      2. Although rodents and rabbits can carry Rabies, no human cases have been attributed to these animals

III. Pathophysiology

  1. Lyssavirus Infection
    1. Rhabdoviridae Family (RNA Viruses)
  2. Transmitted by bite of infected mammals
    1. Saliva, brain and other nerve tissue are infectious
    2. Blood, urine, and stool are not infectious
  3. Highest risk animals
    1. Bats
      1. See Bat Bite
      2. Responsible for most U.S. cases of Rabies (87% of cases 1980-2015)
    2. Dogs
      1. See Dog Bite
      2. Worldwide, these are main vector for infection
      3. However, in U.S. Rabies is less common in dogs (70 cases/year in U.S.)
        1. Responsible for 11 of 31 U.S. human Rabies cases 2003-2016
    3. Cats
      1. See Cat Bite
      2. Most common domesticated animal with Rabies in U.S. (257 cases of cats with Rabies in 2012)
    4. Raccoons
    5. Skunks
    6. Foxes
    7. Coyotes
    8. Bobcats
    9. Woodchucks
    10. Ferrets

IV. Symptoms

  1. Incubation Period: Days to months
  2. Early (Prodromal)
    1. Local radiating Paresthesia from bite site
    2. Malaise
    3. Nausea
    4. Pharyngitis
  3. Late (Neurologic)
    1. Restlessness
    2. Significant Agitation
    3. Hallucinations
    4. Bizarre behavior
    5. Seizures
    6. Aerophobia and Hydrophobia are pathognomonic

V. Signs

  1. Early
    1. Wound Inflammation
    2. Hyperesthesia at wound site
  2. Late
    1. Dysarthria
    2. Hoarseness
    3. Aphonia
    4. Dysphagia for fluids
    5. Shallow or irregular breathing
    6. Seizure
    7. Delirium
    8. Opisthotonos stimulated by lights or noises
    9. Hyperactive Deep Tendon Reflexes
    10. Nuchal Rigidity
    11. Abnormal Babinski Reflex (Up-going toes)
  3. Terminal signs
    1. Flaccid Paralysis
    2. Hospitalization <1 week after symptom onset
    3. Coma within one week of encephalopathy signs
    4. Death

VI. Labs

  1. Live Observation of suspected infected mammal
  2. Rabies Virus Antigen Testing
    1. Saliva contains virus
    2. Brain and spinal cord of suspected infected animal

VII. Management

  1. See Rabies Prophylaxis
  2. See Dog Bite

VIII. Prognosis

  1. Uniformly fatal once patient is symptomatic
  2. Early Postexposure Prophylaxis after Animal Bite is critical

IX. Prevention

  1. Rabies Vaccine
    1. For Rabies Postexposure Prophylaxis and preexposure prophylaxis
  2. Rabies Immunoglobulin
    1. Rabies Postexposure Prophylaxis
  3. Avoid bat exposure
    1. Remove bat roosts from home
    2. Bats trapped within a home living space are more likely to be sick (disabled navigation)
  4. Pets should be vaccinated against Rabies
    1. In U.S., of pets causing a bite evaluated in ER, only 45% of dogs and 8% of cats were vaccinated against Rabies
  5. Test for Rabies in pets who succumb to illness quickly

X. References

  1. Swaminathan and Hope in Herbert (2018) EM:Rap 18(12): 11-2
  2. Messenger (2002) Clin Infect Dis 35:738-47 [PubMed]
  3. Wilde (2003) Clin Infect Dis 37:96-100 [PubMed]

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