What is the appropriate management of a rat bite, including wound irrigation, tetanus prophylaxis, antimicrobial therapy, and rabies post‑exposure prophylaxis?

Rat Bite Treatment

Immediate Wound Management

Thoroughly irrigate the wound with copious sterile saline or water using a 20-mL or larger syringe to generate sufficient pressure—this is the single most critical step to reduce bacterial load and prevent infection. 1

• Remove only superficial debris; avoid aggressive debridement that could unnecessarily enlarge the wound 1
• Do not use iodine- or antibiotic-containing solutions for routine wound cleansing 1
• Do not close rat bite wounds with sutures, as this increases infection risk 1
• The only exception is facial wounds, which may be closed primarily after meticulous irrigation, cautious debridement, and initiation of prophylactic antibiotics 1
• Non-facial wounds may be approximated with Steri-Strips if needed for cosmetic or functional reasons 1

Rationale for Wound Management

Wound cleansing is particularly important because thorough irrigation alone markedly reduces infection risk in animal studies 2. While one older study from 1985 found only a 2% infection rate in uninfected rat bites without prophylactic antibiotics 3, more recent microbiological data from 2014 demonstrates that rat bite wounds harbor approximately 22 different bacterial species, with 72.5% of infections being polymicrobial 4. This suggests the deep puncturing nature of rodent bites warrants more aggressive management than previously thought.

Tetanus Prophylaxis

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

• Prefer Tdap over Td if the patient has never previously received Tdap 1
• For contaminated wounds (all rat bites qualify as contaminated), give tetanus toxoid if more than 5 years have elapsed since the last dose 1
• Tetanus prophylaxis is mandatory, as most rat bite victims are deficient in tetanus immunization 3

Antibiotic Prophylaxis

Prophylactic antibiotics for 3–5 days are indicated for high-risk patients and high-risk wounds, given the polymicrobial nature of rat bite infections. 1, 4

Indications for Prophylactic Antibiotics:

• Immunocompromised patients 1
• Asplenic patients 1
• Advanced liver disease 1
• Pre-existing or resultant edema of the affected area 1
• Moderate to severe injuries, especially to the hand or face 1
• Injuries that may have penetrated the periosteum or joint capsule 1

First-Line Antibiotic Regimen:

Amoxicillin-clavulanate 875/125 mg twice daily is the first-line oral agent, providing essential coverage against both aerobic and anaerobic organisms commonly found in rat bite wounds 1

Alternative Regimens for Penicillin Allergy:

• Doxycycline 100 mg twice daily 1
• Fluoroquinolones (ciprofloxacin, levofloxacin, or moxifloxacin) combined with metronidazole or clindamycin for anaerobic coverage 1

Severe Infections Requiring IV Therapy:

• Ampicillin-sulbactam 1
• Piperacillin-tazobactam 1
• Carbapenems (ertapenem, imipenem, or meropenem) 1

Important Caveat:

While the 1985 study suggested avoiding prophylactic antibiotics due to a low natural infection rate 3, this conflicts with more recent microbiological evidence showing polymicrobial infections with Staphylococcus aureus as the most common isolate, along with numerous aerobic and anaerobic Gram-positive and Gram-negative bacteria 4. Given the deep puncturing nature of rodent bites and the broad range of potential pathogens, prophylactic antibiotics should be strongly considered for high-risk wounds and patients 4.

Rabies Post-Exposure Prophylaxis

Rabies prophylaxis is generally not required for domestic rat bites in the United States, as small rodents are rarely infected with rabies. 2

• Consult local or state health departments before initiating rabies prophylaxis for rodent bites 2
• If rabies exposure is suspected based on local epidemiology or unusual circumstances, previously unvaccinated persons should receive both rabies immune globulin (HRIG) and vaccine 2
• The recommended regimen is 1 dose of HRIG (20 IU/kg body weight) infiltrated around and into the wound, plus 5 doses of rabies vaccine administered on days 0,3,7,14, and 28 2
• HRIG should be administered only once at the beginning of prophylaxis and can be given up to day 7 if not given initially 2

Follow-Up and Monitoring

Arrange follow-up within 24 hours (phone call or office visit) for all outpatients. 1

• Elevate the injured extremity to reduce swelling and promote healing 1
• Monitor closely for signs of infection: increasing pain, redness, swelling, or purulent discharge 1
• Hospitalize the patient if infection progresses despite appropriate antimicrobial therapy 1
• Hand wounds and wounds near joints require particularly close monitoring due to higher risk of septic arthritis and osteomyelitis 1

Special Considerations for Wound Classification:

Recent pediatric data suggests rat bites can be classified into three types: Type I (superficial scratches), Type II (deeper bites with infection/ulceration requiring drainage and debridement), and Type III (full-thickness with tissue loss requiring skin grafting) 5. Most patients do not require hospital admission, and treatment should be primarily conservative wound care management, with surgery reserved for drainage, debridement, or reconstruction 5.