How should a patient bitten by a dog 21 days ago be evaluated and managed?

Management of Dog Bite 21 Days Post-Injury

At 21 days post-exposure, the critical rabies observation period has long passed, and your primary focus should be on evaluating for delayed infection, wound healing complications, and determining if rabies prophylaxis was appropriately administered or is still indicated.

Immediate Assessment Required

Rabies Risk Evaluation - The Critical Priority

If the dog was not observed for 10 days after the bite or if its status is unknown, rabies prophylaxis should be initiated immediately regardless of the 21-day delay, as incubation periods exceeding 1 year have been documented in humans. 1, 2

• If the dog was healthy and available: The standard recommendation is confinement and observation for 10 days; dogs that remain healthy during this period would not have been infectious at the time of the bite 1
• If the dog was stray, unwanted, or unavailable for observation: The patient should have received immediate prophylaxis, which can still be initiated now if not previously given 1, 2
• If the dog showed any illness during observation: It should have been euthanized and tested immediately, with the patient receiving full prophylaxis 1, 2

Post-Exposure Prophylaxis Protocol (If Not Previously Given)

The complete regimen includes both rabies immune globulin (RIG) and vaccine for previously unvaccinated persons, administered as a medical urgency even at 21 days post-exposure. 1, 2, 3

• Vaccine schedule: 4-dose regimen on days 0,3,7, and 14 (or alternative 5-dose regimen on days 0,3,7,14, and 28) 2, 3
• RIG dosing: 20 IU/kg body weight given once on day 0, infiltrated into and around all wounds if anatomically feasible, with remainder given intramuscularly at a site distant from vaccine 2
• Previously vaccinated persons: Require vaccine only (no RIG) with a 2-dose schedule on days 0 and 3 2

Wound and Infection Assessment

Signs of Established or Delayed Infection

At 21 days, most acute infections would have already manifested, but delayed complications can still occur, particularly with deep wounds or inadequate initial treatment.

• Active infection indicators: Purulent drainage, increasing redness, warmth, swelling, fever, red streaking, or lymph node swelling indicate infection requiring systemic antibiotics 4
• Deep structure involvement: Wounds involving tendons, joints, or bone require IV antibiotics and possible surgical intervention 4
• High-risk wound locations: Hand, face, genital, or near-joint bites have significantly higher complication rates including osteomyelitis and septic arthritis 4

Microbiologic Considerations

Infected dog bites yield a median of 5 bacterial isolates per culture, with 60% containing mixed aerobic and anaerobic bacteria. 4, 5

• Common pathogens: Pasteurella species (50% of dog bites), streptococci, staphylococci, fusobacterium, bacteroides, porphyromonas, and prevotella 5
• Antibiotic coverage: Combination beta-lactam/beta-lactamase inhibitor is appropriate empiric therapy based on microbiologic findings 5

Special Populations at Higher Risk

Patients with immunocompromising conditions (asplenia, liver disease, diabetes) are at increased risk of severe sepsis from Capnocytophaga canimorsus and require more aggressive management. 4

Tetanus Prophylaxis Verification

Confirm tetanus immunization status; if the last booster was administered more than 5 years prior to a high-risk injury, tetanus vaccine should have been given during initial treatment. 6

• This is a critical oversight that can lead to severe outcomes, as tetanus can present 4+ days after injury 6

Common Pitfalls to Avoid

• Assuming the 21-day delay eliminates rabies risk: Rabies prophylaxis should be initiated regardless of delay if exposure risk exists 1, 2
• Overlooking deep structure involvement: 20% of dog bites require medical care, and complications can manifest late 4
• Failing to assess geographic rabies epidemiology: In rabies-endemic areas, prophylaxis should have been initiated immediately and discontinued only if the dog remained healthy for 10 days 2
• Inadequate wound assessment: Deep puncture wounds carry higher infection risk even if initially appearing minor 4