What is the treatment for a cat scratch?

Treatment of Cat Scratch

Immediately wash the wound thoroughly with soap and water, ensure tetanus prophylaxis is current, and for uncomplicated cat scratches in immunocompetent patients, antibiotics are generally not required as the condition is self-limited. 1

Immediate Wound Management

• Thoroughly cleanse all cat scratches with soap and water immediately to reduce bacterial load and prevent infection, as this simple measure has been shown to markedly reduce infection risk 1
• Apply a virucidal agent such as povidone-iodine solution to the wound for additional antimicrobial effect 1
• Update tetanus immunization if not current within the past 5-10 years, as animal scratches pose tetanus risk 1, 2
• Elevate the affected extremity if swelling develops to reduce edema and accelerate healing 2

Antibiotic Therapy Decision Algorithm

For Simple Cat Scratches Without Lymphadenopathy

• No antibiotic therapy is required for most immunocompetent patients, as cat scratch disease typically resolves spontaneously within 1-6 months 1, 3, 4, 5
• Monitor for development of regional lymphadenopathy, which typically appears 3 weeks after the scratch but can occur earlier 1, 2

For Cat Scratch Disease With Lymphadenopathy

• Azithromycin is the treatment of choice: 500 mg on day 1, followed by 250 mg daily for 4 additional days (for patients >45 kg) 1
• For patients <45 kg: 10 mg/kg on day 1, then 5 mg/kg daily for 4 additional days 1
• This regimen has been shown in a placebo-controlled trial to achieve 80% regression of lymph node size at 30 days (P = 0.02) 1

For Infected Cat Scratches (Cellulitis/Wound Infection)

• Amoxicillin-clavulanate 875 mg orally twice daily for 7-10 days is first-line therapy, providing coverage against Pasteurella multocida and other common pathogens from cat scratches 2
• Avoid first-generation cephalosporins (like cephalexin) as they have poor activity against P. multocida, a common pathogen in cat bites and scratches 2
• For moderate to severe infection requiring hospitalization: ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours 2

For Immunocompromised Patients (HIV, Transplant, Immunosuppressive Therapy)

• Erythromycin 500 mg four times daily or doxycycline 100 mg twice daily for 2 weeks to 2 months is recommended for bacillary angiomatosis, which can develop in immunocompromised patients 1
• These patients require more aggressive and prolonged treatment due to risk of disseminated disease and life-threatening complications 6
• Alternative effective agents include rifampin, ciprofloxacin, gentamicin, trimethoprim-sulfamethoxazole, or clarithromycin 3, 7

Assessment for Systemic Involvement

• Check vital signs: temperature ≥38.5°C or pulse ≥100 bpm indicates systemic involvement requiring more aggressive treatment 2
• Measure extent of erythema and induration: >5 cm suggests invasive infection requiring antibiotics 2
• Assess for red streaking (lymphangitis), warmth, tenderness, and purulent drainage 2
• Palpate regional lymph nodes (epitrochlear and axillary for arm scratches) for enlargement or tenderness 2

Critical Pitfalls to Avoid

• Do not proceed with elective surgery in the presence of active soft tissue infection from a cat scratch, as this dramatically increases surgical site infection risk and systemic complications 2
• Surgery should be delayed until complete resolution of erythema, swelling, and systemic symptoms, typically requiring 2-4 weeks 2
• Do not use first-generation cephalosporins for infected cat scratches due to inadequate coverage of P. multocida 2
• Do not squeeze lesions to produce material for culture, as this can worsen infection 1

Rabies Consideration

• If the cat is stray, unwanted, or behaving abnormally, observe the animal for 10 days or euthanize immediately for rabies testing 1
• A currently vaccinated domestic cat is unlikely to be infected with rabies 1
• Unprovoked attacks are more likely to indicate rabies than provoked attacks (such as when attempting to feed or handle the animal) 1
• If rabies cannot be ruled out, initiate postexposure prophylaxis with rabies immune globulin (20 IU/kg) infiltrated around the wound plus rabies vaccine series (5 doses over 28 days) 1

Follow-Up and Monitoring

• Reassess in 48-72 hours to ensure antibiotic efficacy and clinical improvement 2
• Monitor for atypical complications including encephalopathy, hepatosplenic involvement, osteomyelitis, endocarditis, or ocular involvement (Parinaud oculoglandular syndrome, stellate neuroretinitis) 1, 3, 5, 7
• These severe manifestations occur in <2-10% of cases but require more aggressive antibiotic therapy 1