What is the recommended treatment for a rat bite?

Rat Bite Management

Immediate Wound Care

All rat bite wounds must be immediately and thoroughly washed with soap and water for at least 15 minutes, as this single intervention reduces infection risk more effectively than any other measure. 1

• Irrigate copiously with sterile normal saline or water to remove debris and reduce bacterial load 2
• Avoid closing infected wounds; non-infected wounds seen early (<8 hours) may be approximated with Steri-Strips rather than sutures 2
• Facial wounds are an exception and may be closed primarily after meticulous irrigation and prophylactic antibiotics 2

Tetanus Prophylaxis

Tetanus prophylaxis is mandatory for all rat bites, as most patients are deficient in tetanus immunization. 3

• Administer tetanus toxoid (0.5 mL intramuscularly) if vaccination status is outdated or unknown 2

Rabies Risk Assessment

Rabies prophylaxis is generally NOT required for rat bites in the United States, as small rodents (including rats) are not considered significant rabies vectors. 4

• Rabies transmission from rats is extraordinarily rare and typically not a concern 2
• If rabies exposure is suspected in exceptional circumstances, previously unvaccinated persons should receive both rabies immune globulin (RIG) at 20 IU/kg and a 4-dose vaccine series on days 0,3,7, and 14 1
• The full RIG dose should be infiltrated around and into the wound if anatomically feasible, with remaining volume given intramuscularly at a site distant from vaccine administration 1

Antibiotic Management

Prophylactic Antibiotics

Prophylactic antibiotics are NOT routinely recommended for uninfected rat bites, as the natural infection rate is only 2%. 3

• However, given the deep puncturing nature of rodent bites and polymicrobial bacterial flora (72.5% of infections are polymicrobial), consider prophylaxis for high-risk wounds 5
• Rat bite wounds can harbor approximately 22 different bacterial species, with Staphylococcus aureus being most common 5

Treatment of Infected Wounds

For infected rat bite wounds, amoxicillin-clavulanate is the first-line oral antibiotic therapy, providing broad coverage for the polymicrobial nature of these infections. 2

• Oral first-line: Amoxicillin-clavulanate 2
• Oral alternatives for penicillin allergy:
  • Doxycycline 2
  • Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) plus metronidazole or clindamycin 2
• Intravenous first-line: Ampicillin-sulbactam or piperacillin-tazobactam 2
• Intravenous alternatives: Second-generation cephalosporins (cefoxitin) or carbapenems (ertapenem, imipenem, meropenem) 2

Wound Classification and Management

Type I: Superficial Scratches

• Conservative wound care management only 6
• No hospital admission or antibiotics typically required 6

Type II: Deeper Bites with Infection/Ulceration

• May require urgent drainage and debridement 6
• Consider antibiotic therapy based on clinical signs of infection 6

Type III: Full-Thickness with Tissue Loss

• Requires skin grafting 6
• Surgical consultation indicated 6

Special Considerations

• Rat bite fever: A rare but serious complication caused by Streptobacillus moniliformis, presenting with fever, rash, and polyarthritis in up to 50% of cases 7, 8
• Diagnosis can be difficult as fever may be absent 8
• Treatment with ceftriaxone for 10 days is effective 7
• Elevate injured extremities if swollen 2
• Follow up within 24 hours for all outpatients 2
• Consider hospitalization if infection progresses despite appropriate antimicrobial therapy 2

Common Pitfalls

• Most rat bites (72%) occur during sleep, affecting exposed areas of upper extremities and face 3
• Few wounds display obvious signs of inflammation initially 6
• Do not routinely prescribe prophylactic antibiotics for clean, uninfected wounds—the infection rate is very low 3
• Ensure adequate wound irrigation, as this is more important than antibiotic prophylaxis 1, 3