What is the treatment for a rat bite?

Treatment of Rat Bites

The optimal treatment for rat bites includes immediate thorough wound cleansing, tetanus prophylaxis, consideration of antibiotic therapy, and assessment for potential rat bite fever, with rabies prophylaxis rarely needed for domestic rats.

Initial Wound Management

• Immediate wound cleansing:

  • Thoroughly wash all bite wounds with soap and water 1
  • Consider irrigation with povidone-iodine solution to decrease bacterial infection risk 1
  • Remove any superficial debris from the wound 1

• Wound closure considerations:

  • Avoid suturing infected wounds 1
  • For fresh, uninfected wounds (<8 hours), consider approximation with Steri-Strips rather than sutures 1
  • Facial wounds may be an exception and can be closed primarily with proper wound care and prophylactic antibiotics 1

Tetanus Prophylaxis

• Tetanus prophylaxis is mandatory for rat bites 2
• Administer tetanus toxoid (0.5 mL intramuscularly) if:
  • Tetanus vaccination status is outdated
  • Vaccination status is unknown 1

Antibiotic Therapy

Prophylactic Antibiotics

• While one study showed only 2% natural infection rate without prophylactic antibiotics 2, more recent evidence suggests considering prophylaxis due to:
  • Deep puncturing nature of rodent bites 3
  • Potential for polymicrobial infections 3

Recommended Antibiotics

• For empiric therapy or if infection develops:
  • First-line: Amoxicillin-clavulanate (provides broad coverage) 1
  • Alternatives for penicillin-allergic patients: Doxycycline or clindamycin 1
  • For confirmed rat bite fever: Penicillin G (IV) followed by oral amoxicillin or doxycycline 4, 5

Monitoring and Follow-up

• Follow up within 24 hours either by phone or office visit 1
• Monitor for signs of:
  • Local infection: increased redness, swelling, or purulent discharge
  • Rat bite fever: fever, rash (especially on extremities, palms and soles), myalgia, and arthralgia occurring typically 1-2 weeks after bite 6, 4, 5

Special Considerations

Rat Bite Fever

• Caused primarily by Streptobacillus moniliformis
• Can lead to serious complications including osteomyelitis and endocarditis if untreated 6
• Diagnosis often requires specialized techniques (MALDI-TOF or molecular biology) 6
• Treatment: Penicillin G IV initially, followed by oral amoxicillin or doxycycline 4, 5

Rabies Prophylaxis

• Rarely required for domestic rat bites 2
• Consider for wild or feral rat bites in areas with high rabies prevalence
• Consult local department of health about risks and benefits if concerned 1

Bacterial Pathogens to Consider

• Common isolates from rat bite wounds:
  • Staphylococcus species (including S. aureus) 2, 3
  • Streptobacillus moniliformis (rat bite fever) 6, 4, 5
  • Multiple aerobic and anaerobic bacteria (72.5% of infections are polymicrobial) 3

Pitfalls and Caveats

• Rat bite fever can be easily missed despite adequate history and physical examination 4
• Delayed presentation is common as symptoms of rat bite fever typically develop 1-2 weeks after the bite 6, 4, 5
• Patients with comorbidities (e.g., liver cirrhosis) may be at higher risk for complications 5
• Consider elevation of the affected extremity if significant swelling is present 1