How should I manage a rat bite, including wound care, tetanus prophylaxis, rabies post‑exposure prophylaxis, and appropriate antibiotic therapy?

Rat Bite Treatment Protocol

For rat bites, prophylactic antibiotics are NOT routinely recommended due to the low natural infection rate of only 2%, but meticulous wound care with copious irrigation, tetanus prophylaxis, and close monitoring for infection are mandatory. 1

Immediate Wound Management

• Irrigate the wound immediately and thoroughly with copious amounts of sterile saline or water – this is the single most important intervention to reduce bacterial load and prevent infection. 2, 3

• Use a 20-mL or larger syringe to generate adequate pressure for effective irrigation. 4

• Remove only superficial debris; avoid aggressive debridement that could unnecessarily enlarge the wound. 5

• Do NOT use iodine- or antibiotic-containing solutions for routine wound cleansing. 5, 4

• Do NOT close rat bite wounds except for facial wounds, which may be closed primarily after meticulous irrigation, cautious debridement, and preemptive antibiotics. 2

• Non-facial wounds may be approximated with Steri-Strips if needed, but avoid sutures. 5

Tetanus Prophylaxis

• Administer tetanus toxoid (0.5 mL intramuscularly) if the patient has not received a booster within the past 10 years. 2, 1

• Tdap is preferred over Td if the patient has not previously received Tdap. 2

• For contaminated wounds (all rat bites qualify), give tetanus toxoid if more than 5 years have passed since the last dose. 4

Antibiotic Therapy Decision Algorithm

Prophylactic Antibiotics (3-5 days) ARE indicated for:

• Immunocompromised patients 2
• Asplenic patients 2
• Advanced liver disease 2
• Preexisting or resultant edema of the affected area 2
• Moderate to severe injuries, especially to the hand or face 2
• Injuries that may have penetrated the periosteum or joint capsule 2

Prophylactic Antibiotics are NOT indicated for:

• Simple, uninfected rat bite wounds in immunocompetent patients, as the natural infection rate is only 2% 1

First-Line Antibiotic Choice (when indicated):

• Amoxicillin-clavulanate (875/125 mg twice daily) is the recommended agent, providing coverage against both aerobic and anaerobic bacteria. 2, 5, 6

Alternative Oral Regimens for Penicillin Allergy:

• Doxycycline 100 mg twice daily 5, 6
• Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) PLUS metronidazole or clindamycin 5

Intravenous Therapy for Severe Infections:

• Ampicillin-sulbactam, piperacillin-tazobactam, or carbapenems (ertapenem, imipenem, meropenem) 2, 5

If Infection Develops (treat for 7-10 days):

• First-generation cephalosporins (cefazolin) or penicillinase-resistant penicillins (nafcillin, oxacillin) are sufficient for treating established rat bite infections, as the most common bacterial isolates are Staphylococcus epidermidis (43% of positive cultures). 1

Rabies Prophylaxis

• Rabies prophylaxis is generally NOT required for rat bites in the United States, as rodents (including rats) are rarely found to be infected with rabies and have not been known to cause human rabies in the U.S. 7

• However, consult local health officials to determine if vaccination should be initiated based on regional epidemiology. 2, 7

• If rabies prophylaxis is indicated (extremely rare), previously unvaccinated persons should receive both rabies immune globulin (20 IU/kg body weight infiltrated around the wound) and rabies vaccine series (days 0,3,7,14, and 28). 7

Follow-Up and Monitoring

• Elevate the injured extremity to reduce swelling and accelerate healing. 5

• Follow up within 24 hours by phone or office visit for all outpatients. 5, 4

• Monitor closely for signs of infection: increasing pain, redness, swelling, or purulent discharge. 6

• Consider hospitalization if infection progresses despite appropriate antimicrobial therapy. 5

Common Pitfalls and Caveats

• The most common error is prescribing prophylactic antibiotics unnecessarily – 72% of rat bites occur during sleep (explaining why 84% involve exposed areas of upper extremities and face), but the infection rate remains only 2% without antibiotics. 1

• Inadequate irrigation is the primary cause of subsequent infection – copious irrigation may be more important than antibiotic prophylaxis. 3, 8

• Premature wound closure leads to dehiscence and infection – when in doubt, cover the wound with a sterile dressing and allow healing by secondary intention or delayed closure. 9

• Hand wounds and wounds near joints require special attention due to higher risk of complications including septic arthritis and osteomyelitis, and should receive prophylactic antibiotics. 2, 4