Rabies

Background

  • Almost always fatal (diagnosis frequently made postmortem)
  • Indication for prophylaxis:
    • Bite or salivary exposure from bat, or mammalian carnivore
    • Close proximity with unknown salivary exposure (e.g. live/dead bat in room)
  • Prophylaxis not needed if non-salivary exposure, or if bird, reptile, or rodent (rare cases)

Clinical Features

Man with rabies.

Clinical rabies is incredibly rare.

  • Incubation period = ~20-90 days, but may be shorter or longer

Encephalitic form

  • Hyperexcitability, disorientation, bizarre behavior, hallucinations
  • Autonomic dysfunction (e.g. hypersalivation)

Paralytic form

  • Paresis in bitten extremity → quadriparesis, bilateral facial weakness → coma, organ failure
  • Hydrophobia (50%) --> spasms of larynx, pharynx, diaphragm
  • Aerophobia (9%) --> spasms of larynx, pharynx, diaphragm in response to drafts of air (pathognomonic)[1]
  • Death from various complications: pituitary complications, respiratory dysfunction, cardiac dysfunction, autonomic dysfunction.

Differential Diagnosis

Jaw Spasms

Evaluation

Algorithm for Prophylaxis

Animal was captured

Is animal dog or cat?

  • Yes: Observe 10 days, if abnormal, euthanize and treat patient with the vaccine and RIG. Then patient treatment can be discontinued if the animal pathology is negative for rabies
  • No: Euthanize animal and treat patient with vaccine and RIG. Discontinue if animal pathology is negative for rabies
Animal was not captured

Is animal dog or cat?

  • Yes: Give vaccine and RIG only if rabies risk for species in area
  • No: Treat with full course vaccine and RIG

Management

Prophylaxis

Immunocompetent + NOT Vaccinated

  • Clean the wound (e.g. copious irrigation)
  • Rabies vaccine (human diploid cell vaccine)
    • 1mL IM on days: 0, 3, 7, 14[2]
    • Give in deltoid (not buttock), since Ab not created in fat cells
  • AND, Rabies immune globulin
    • 20 IU/kg subcutaneous
    • Infiltrate around wound if possible
    • Place remainder opposite arm of vaccine
    • Can administer up to 7 days after the first vaccine dose

Immunocompetent + Vaccinated

  • Clean the wound (e.g. copious irrigation)
  • Rabies vaccine (human diploid cell vaccine)
    • 1mL IM on days: 0 and 3
    • Give in deltoid (not buttock), since Ab not created in fat cells
  • NO rabies immune globulin

Immuno-compromised

  • Clean the wound (e.g. copious irrigation)
  • Rabies vaccine (human diploid cell vaccine)
    • 1mL IM on days: 0, 3, 7, 14, and 28[2]
    • Give in deltoid (not buttock), since Ab not created in fat cells
  • AND, Rabies immune globulin
    • 20 IU/kg subcutaneous
    • Infiltrate around wound if possible, except for digits and the penis
    • Place remainder opposite arm of vaccine
    • Can administer up to 7 days after the first vaccine dose

Disposition

  • Patient needing prophylaxis: outpatient
  • Clinical rabies: admit

See Also

References

  1. Petersen BW, Rupprecht CE. Human Rabies Epidemiology and Diagnosis. US Centers for Disease Control and Prevention, 2011. https://www.intechopen.com/books/non-flavivirus-encephalitis/human-rabies-epidemiology-and-diagnosis (Accessed on January 15, 2021).
  2. 2.0 2.1 Use of a Reduced (4-Dose) Vaccine Schedule for Postexposure Prophylaxis to Prevent Human Rabies. http://www.cdc.gov/rabies/resources/acip_recommendations.html