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)
• Death from various complications: pituitary complications, respiratory dysfunction, cardiac dysfunction, autonomic dysfunction.

Differential Diagnosis

Jaw Spasms

• Acute tetanus
• Akathisia
• Conversion disorder
• Drug toxicity (anticholinergic, phenytoin, valproate, carbamazepine)
• Dystonic reaction
• Electrolyte abnormality
  • Hypocalcemic tetany
  • Magnesium
• Mandible dislocation
• Meningitis
• Peritonsillar abscess
• Rabies
• Seizure
• Strychnine poisoning
• Stroke
• Temporomandibular disorder
• Torticollis

Evaluation

Algorithm for Prophylaxis

Animal was captured

Is animal dog or cat?

• Yes: Observe 10 days, if abnormal, euthanize animal and treat patient with the vaccine and RIG. 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
  • 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
  • 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

• Mammalian bites