What is the risk of rabies infection from a cat bite and what is the recommended post-exposure prophylaxis (PEP)?

Rabies Risk from Cat Bites and Post-Exposure Prophylaxis

Cat bites carry a significant rabies risk when the animal's vaccination status is unknown or the animal cannot be observed for 10 days, and post-exposure prophylaxis (PEP) should be initiated immediately with both rabies immune globulin (RIG) and a 4-dose vaccine series. 1

Risk Assessment for Cat Bites

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

1. Animal Availability and Observation Status

• Healthy domestic cats that can be confined and observed for 10 days do not require immediate PEP - treatment is only initiated if the animal develops signs of rabies during this observation period 1, 2
• If the cat is unavailable for observation (stray, escaped, or died before completing 10 days), PEP must be initiated immediately regardless of the animal's apparent health at the time of the bite 3, 4
• The 10-day observation period is prospective only - the animal must remain alive and healthy throughout the entire period for this approach to be valid 3

2. Regional Epidemiology

• In the United States, rabies in cats varies by region, with higher risk along the US-Mexico border and in areas with enzootic wildlife rabies 4, 2
• Stray or unowned cats carry substantially higher risk than owned, vaccinated cats 4, 2
• Over 50% of human rabies cases in the US result from exposures to animals outside the United States, making travel history critical 2

3. Nature of Exposure

• Any penetration of skin by teeth constitutes a bite exposure requiring evaluation for PEP 2
• Cat bites typically cause deep puncture wounds that carry the highest infection risk, particularly on the hands 5, 6, 7
• Scratches, abrasions, or mucous membrane contact with saliva also constitute rabies exposure 2

Post-Exposure Prophylaxis Protocol

For Previously Unvaccinated Persons

The complete PEP regimen consists of:

Immediate Wound Management (Day 0)

• Thoroughly wash and flush all wounds with soap and water for approximately 15 minutes - this alone markedly reduces rabies transmission risk in animal studies 1, 3, 2
• Use povidone-iodine solution if available for additional virucidal effect 1
• Assess for tetanus prophylaxis needs 1, 5

Rabies Immune Globulin (RIG) - Day 0 Only

• Administer 20 IU/kg body weight on day 0 1, 2
• Infiltrate the full dose around and into the wound(s) if anatomically feasible, with any remaining volume injected intramuscularly at a site distant from vaccine administration 1
• RIG can be given up to day 7 after the first vaccine dose, but beyond day 7 it is not indicated as antibody response to vaccine is presumed to have occurred 1, 2
• Never administer RIG in the same syringe or same anatomical site as vaccine 1

Rabies Vaccine Schedule

• Current ACIP recommendations specify a 4-dose schedule: days 0,3,7, and 14 (the 5th dose on day 28 was eliminated in 2010) 1
• Use either human diploid cell vaccine (HDCV) or purified chick embryo cell vaccine (PCECV), 1.0 mL intramuscularly 1
• Administer in the deltoid area for adults and older children; use anterolateral thigh for infants and young children - never use the gluteal area 1

For Previously Vaccinated Persons

• Administer vaccine only (no RIG) on days 0 and 3 1
• This applies to anyone who has completed a pre-exposure or post-exposure vaccination series with cell culture vaccine 1

Critical Timing Considerations

• Rabies PEP is a medical urgency, not a medical emergency - it should be initiated as soon as possible but delayed treatment remains highly effective 1, 4
• PEP should be administered regardless of the length of delay as long as the exposed person shows no clinical signs of rabies 3
• Rabies incubation periods exceeding 1 year have been documented in humans, making even significantly delayed treatment worthwhile 3
• No failures of modern cell culture vaccines have been documented when properly administered, even with delayed initiation 1, 3

Cost-Effectiveness Context

• The cost-effectiveness analysis shows that PEP for cat bites from untested animals costs approximately $2.9 million per life saved 1
• Despite this high cost per life saved, PEP is always recommended when the animal cannot be tested or observed because rabies is nearly 100% fatal once clinical symptoms develop 1, 8
• The 4-dose schedule saves approximately $16.6 million annually to the US healthcare system compared to the previous 5-dose regimen 1

Common Pitfalls to Avoid

• Do not wait to locate an escaped cat before initiating PEP - begin immediately if the animal is unavailable 4
• Do not exceed the recommended RIG dose (20 IU/kg) as this can partially suppress active antibody production 1
• Do not fail to infiltrate RIG into the wound site - inadequate local infiltration reduces effectiveness 1, 4
• Do not consider the observation period valid if the animal dies before completing 10 days - PEP must be initiated 3
• Avoid primary closure of cat bite wounds when possible, particularly puncture wounds on the hands, due to high infection risk 1, 6

Antibiotic Prophylaxis

• Amoxicillin-clavulanate is the first-line antibiotic for cat bite prophylaxis due to high risk of Pasteurella multocida infection (isolated in over 50% of cat bites) 5, 6, 7
• Cat bites to the hand carry the greatest infection risk and warrant antibiotic prophylaxis 5, 6