HRIG for Cat Scratch: Risk Assessment-Based Decision
HRIG is NOT indicated for a simple cat scratch unless the cat is rabid, suspected rabid, or unavailable for observation—the critical decision hinges on whether the cat can be observed for 10 days and its current health status. 1, 2
Immediate Wound Management (Required Regardless of HRIG Decision)
- Thoroughly wash the scratch with soap and water for 15 minutes immediately—this is the single most effective measure for preventing rabies and reduces infection risk markedly. 1, 3
- Apply povidone-iodine solution or similar virucidal agent to the wound site if available. 3, 4
- Assess for tetanus prophylaxis needs based on immunization status. 1, 3
- Consider antibiotic prophylaxis (amoxicillin-clavulanate) only if the scratch is deep or shows signs of infection, as cat scratches carry risk of Bartonella henselae (cat-scratch disease) and bacterial infection. 3, 5
Decision Algorithm for HRIG Administration
Scenario 1: Healthy Cat Available for 10-Day Observation
- Do NOT give HRIG or rabies vaccine—simply observe the cat for 10 days. 1, 2
- If the cat remains healthy throughout the observation period, no postexposure prophylaxis is needed. 2
- If the cat develops signs of rabies during observation, immediately begin HRIG (20 IU/kg) plus rabies vaccine series. 1, 2
Scenario 2: Cat is Rabid or Suspected Rabid
- Immediately administer both HRIG and rabies vaccine—this is the standard postexposure prophylaxis for category III exposures (scratches with broken skin). 1, 2
- Give HRIG at 20 IU/kg body weight: infiltrate up to half the dose around and into the wound if anatomically feasible, inject remainder intramuscularly in the gluteal area. 1, 2
- Administer rabies vaccine (HDCV or PCECV) on days 0,3,7, and 14 (4-dose schedule for immunocompetent patients). 6
- Never give HRIG in the same syringe or anatomical site as the vaccine. 1, 2
Scenario 3: Cat's Status Unknown (Escaped/Unavailable)
- Consult local public health officials, but generally treat as if rabid and administer HRIG plus vaccine series, as scratches constitute nonbite exposures that can transmit rabies when contaminated with saliva. 2
- The combination of HRIG and vaccine is recommended for both bite and nonbite exposures regardless of the interval between exposure and treatment initiation. 1
Scenario 4: Previously Vaccinated Patient
- Do NOT give HRIG—it is contraindicated in previously vaccinated persons as it may suppress the anamnestic antibody response. 4, 6
- Give only a 2-dose vaccine series (days 0 and 3) for immunocompetent patients with prior complete vaccination. 4, 6
- Exception: Immunocompromised patients require the full 5-dose schedule (days 0,3,7,14,28) even with prior vaccination history. 4, 6
Critical Timing Considerations
- HRIG can be administered up to day 7 after the first vaccine dose if not given initially—beyond day 7, HRIG is not indicated as vaccine-induced antibody response is presumed to have occurred. 1, 2
- Begin treatment immediately after exposure (within 24 hours ideally), though even delayed treatment is indicated as rabies incubation periods exceeding 1 year have been documented. 1, 4
- HRIG provides immediate passive antibody protection during the critical first 7 days before vaccine-induced antibodies develop. 7, 8
Common Pitfalls to Avoid
- Do not give HRIG to healthy, vaccinated cats that can be observed—this represents unnecessary treatment and cost. 3, 2
- Never administer more than the recommended 20 IU/kg dose of HRIG, as excess may partially suppress active antibody production. 1
- Do not inject rabies vaccine in the gluteal area (use deltoid in adults, anterolateral thigh in children), as this results in lower neutralizing antibody titers. 1, 6
- Avoid inadequate wound cleaning—this is the most important initial step and more critical than any subsequent intervention. 3