Do I need post-exposure prophylaxis (PEP) for a rat bite?

Rabies Post-Exposure Prophylaxis for Rat Bites

Rabies post-exposure prophylaxis (PEP) is generally NOT required for rat bites, as small rodents like rats are rarely infected with rabies and have not been known to transmit rabies to humans. 1

Risk Assessment for Rodent Bites

• Small rodents (including rats, mice, hamsters, guinea pigs, gerbils, and chipmunks) are almost never found to be infected with rabies and have not been documented to transmit rabies to humans 1
• According to the Advisory Committee on Immunization Practices (ACIP), "bites from squirrels, hamsters, guinea pigs, gerbils, chipmunks, rats, mice, other small rodents, rabbits, and hares almost never require antirabies post-exposure prophylaxis" 2
• While woodchucks accounted for 93% of the 371 cases of rabies among rodents reported to CDC from 1990-1996 in areas with endemic raccoon rabies, rats were not significantly represented in these statistics 1

Decision Algorithm for Rat Bites

1. Initial wound management (required for ALL bites):

   • Immediate and thorough washing of all bite wounds with soap and water for 15 minutes 1, 2
   • Apply a virucidal agent such as povidone-iodine solution to the wound 1
   • Assess need for tetanus prophylaxis and antibiotics for bacterial infection 1, 2

2. Rabies risk assessment:

   • For rat bites specifically: PEP is not routinely recommended 1, 2
   • Consult local/state health department in all cases involving rodents before initiating rabies PEP 1

3. Consider other rat-associated infections:

   • Rat bite fever, caused by Streptobacillus moniliformis, is a more significant concern with rat bites than rabies 3, 4
   • Symptoms include fever, rigors, polyarthralgias, and can be fatal (10% mortality) if untreated 4
   • Appropriate antibiotics should be considered for prevention/treatment of rat bite fever 5, 4

Special Considerations

• The severity of rat bite injuries can vary from superficial scratches to full-thickness wounds with tissue loss, but this classification relates to wound management rather than rabies risk 6
• Even in areas with endemic wildlife rabies, rats remain an extremely low-risk species for rabies transmission 1
• While the ACIP guidelines are clear about the minimal risk from rat bites, always follow local public health authority recommendations, as they may have region-specific guidance 1

Important Caveats

• If the rat's behavior was highly unusual (unprovoked aggression, neurological symptoms), consultation with public health authorities is still warranted, though rabies remains extremely unlikely 1
• The risk of bacterial infection, particularly rat bite fever, is a more significant concern than rabies with rat bites 3, 4
• Fatal cases of rat bite fever have been reported, highlighting the importance of appropriate antibiotic treatment rather than rabies prophylaxis 3, 7

In summary, while dog and cat bites often warrant consideration of rabies PEP depending on circumstances, rat bites almost never require rabies prophylaxis, but should be properly cleaned and evaluated for other infectious risks.