What are the indications for post-exposure prophylaxis (PEP) and rabies treatment after a dog bite?

Indications for Rabies Post-Exposure Prophylaxis After a Dog Bite

Rabies post-exposure prophylaxis (PEP) should be initiated immediately for any dog bite when the dog cannot be observed for 10 days or shows signs of rabies, when the dog's vaccination status is unknown or inadequate, or when the bite occurs in a region where canine rabies is endemic. 1, 2

Risk Assessment Framework

The decision to initiate PEP depends on three critical factors that must be evaluated systematically:

1. Type of Exposure

Any penetration of skin by teeth constitutes a bite exposure requiring risk assessment. 1, 2

• All bites, regardless of body site or visible trauma severity, represent potential rabies transmission risk 1
• Nonbite exposures (scratches, abrasions, or mucous membrane contact with saliva) also warrant evaluation 2
• Indirect contact such as petting, handling, or contact with blood/urine/feces does NOT require PEP 1, 2

2. Animal Availability and Observation Status

For healthy domestic dogs that bite, the standard protocol requires a 10-day observation period. 1, 3

If Dog is Available and Healthy:

• Confine and observe the dog for 10 days 1
• Do NOT initiate PEP during this observation period 2
• If the dog remains healthy for the full 10 days, PEP is not needed 2
• If the dog develops ANY illness or signs suggestive of rabies during observation, immediately euthanize, test, and begin PEP 1

If Dog is NOT Available for Observation:

• Begin PEP immediately if the dog is stray, unwanted, escaped, or died before completing 10 days 1, 3, 2
• The observation period must be prospective—the animal must be alive and healthy throughout the entire 10 days 3
• If the dog is euthanized or dies before day 10, the observation approach is invalid and PEP should start 3

If Dog is Rabid or Suspected Rabid:

• Immediately begin PEP without waiting for laboratory confirmation 2

3. Regional Epidemiology and Vaccination Status

A currently vaccinated dog is unlikely to become infected with rabies and poses minimal risk. 1, 4

• In the United States, dog rabies is most common along the US-Mexico border 1
• In developing countries where dogs are the major rabies vector, exposures represent significantly increased transmission risk 1
• An unprovoked attack is more likely to indicate rabies than a provoked attack 1, 2
• Consult local or state public health officials regarding regional rabies epidemiology 1, 2

Complete PEP Protocol for Previously Unvaccinated Persons

When PEP is indicated, administer both rabies immune globulin (RIG) and vaccine immediately. 1, 2

Immediate Wound Management (Critical First Step):

• Thoroughly wash all bite wounds with soap and water for approximately 15 minutes 1, 5
• Irrigate with povidone-iodine solution or similar virucidal agent if available 1
• This wound cleansing alone markedly reduces rabies likelihood in animal studies 1, 3
• Administer tetanus prophylaxis and bacterial infection control measures as indicated 1, 2

Rabies Immune Globulin (RIG):

• Dose: 20 IU/kg body weight 3, 2
• Infiltrate as much as anatomically feasible around the wound 3, 2
• Inject remaining volume intramuscularly at a site distant from vaccine injection 3
• RIG should only be given if within 7 days of exposure; omit if beyond day 7 3

Rabies Vaccine Schedule:

• 5 doses administered on days 0,3,7,14, and 28 1, 3, 2
• First dose should be given as soon as possible (day 0) 1, 2
• Administer intramuscularly at a different site from RIG 3

Modified Protocol for Previously Vaccinated Persons

Individuals with documented prior rabies vaccination require only 2 vaccine doses (days 0 and 3) without RIG. 6

• This modified regimen exploits the rapid anamnestic immune response in previously vaccinated persons 6
• Exception: Immunosuppressed patients require the full 5-dose regimen with RIG regardless of prior vaccination 6

Critical Timing Considerations

PEP should be administered regardless of delay, provided the exposed person shows no clinical signs of rabies. 1, 3

• Rabies incubation periods exceeding 1 year have been documented in humans 1, 3
• PEP is a "medical urgency, not a medical emergency"—start as soon as possible but delayed treatment remains highly effective 1, 3
• No documented failures of modern cell culture vaccines when properly administered, even if started late 3

Common Pitfalls to Avoid

• Do not administer unnecessary PEP to exposures from healthy, vaccinated pets that can complete 10-day observation 4
• Do not skip wound cleansing—this is the single most important initial preventive measure 1, 3
• Do not assume the observation period is retrospective—if the dog died or was killed before day 10, observation is invalid 3
• Do not give RIG beyond day 7 of the vaccine series, as it may interfere with vaccine-induced immunity 3
• Do not inject RIG and vaccine at the same anatomical site 3