Cat Scratch Disease: Symptoms and Treatment
Clinical Presentation
Cat scratch disease typically presents with a papule or pustule developing 3-30 days after a cat scratch or bite, followed by regional lymphadenopathy appearing approximately 3 weeks after inoculation. 1
Classic Symptoms
- Skin lesion at inoculation site: A papule or pustule forms at the site of the scratch or bite within 3-30 days 1
- Regional lymphadenopathy: Tender, swollen lymph nodes develop about 3 weeks after exposure, most commonly in the epitrochlear and axillary regions 1, 2
- Constitutional symptoms: Fever (≥38.5°C), headache, chills, and malaise may accompany the lymphadenopathy 3, 4
- Natural course: Lymphadenopathy generally resolves within 1-6 months, with suppuration occurring in approximately 10% of cases 1
Atypical Presentations (≤2% of cases)
- Parinaud oculoglandular syndrome: Conjunctival involvement with preauricular lymphadenopathy 5
- Hepatosplenic disease: Liver and splenic microabscesses 5, 6
- Neurological complications: Encephalopathy, meningoencephalitis, or stellate neuroretinitis 5, 7
- Musculoskeletal involvement: Osteomyelitis or paravertebral involvement 5, 6
- Persistent fever without localizing signs 5
- Vasculitic-like skin lesions 8
Immunocompromised Patients
- Bacillary angiomatosis: Vascular proliferative lesions 5, 7
- Bacillary peliosis: Vascular lesions in liver and spleen 5
- Relapsing bacteremia with fever 5
Diagnostic Approach
Clinical Diagnosis
- History of cat exposure: Obtain detailed history of cat scratches, bites, or contact with kittens 1, 7
- Physical examination findings: Measure extent of erythema and induration (>5 cm suggests invasive infection), assess for warmth, tenderness, purulent drainage, and red streaking indicating lymphangitis 2
- Vital signs: Temperature ≥38.5°C or pulse ≥100 bpm indicates systemic involvement requiring more aggressive treatment 2
Laboratory Testing
- Serology: High titers (>1:256) of IgG antibody to Bartonella henselae support diagnosis 7
- Cross-reactivity caveat: Be aware of potential cross-reactivity between B. henselae and B. quintana 1
- PCR testing: Valuable for atypical presentations, especially from tissue specimens 1
- Warthin-Starry silver stain: Can confirm diagnosis from infected lymph node tissue, though cannot differentiate Bartonella species 1
Treatment
Uncomplicated Cat Scratch Disease
For patients with typical lymphadenopathy, azithromycin is the recommended treatment, with dosing of 500 mg on day 1 followed by 250 mg daily for 4 additional days for patients >45 kg. 1, 2
- Pediatric dosing (<45 kg): 10 mg/kg on day 1, then 5 mg/kg daily for 4 more days 1, 9
- Clinical efficacy: Azithromycin therapy is associated with more rapid diminution in size of infected lymph nodes 5
- Self-limited nature: Most cases in immunocompetent hosts resolve without antibiotic therapy, though treatment accelerates recovery 5, 7
Infected Cat Scratch (Soft Tissue Infection)
For mild to moderate soft tissue infection from a cat scratch, amoxicillin-clavulanate 875 mg orally twice daily for 7-10 days is first-line therapy. 2, 9
- Rationale: Provides optimal coverage against Pasteurella multocida and other common pathogens from cat scratches 2, 9
- Severe infection requiring hospitalization: Ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours 2
- Combined therapy: Add azithromycin if cat scratch disease with lymphadenopathy is confirmed or highly suspected 2
Alternative Regimens for Penicillin Allergy
- Doxycycline: 100 mg twice daily for adults, with excellent activity against P. multocida 9
- Duration for cat scratch disease: 10-14 days when using doxycycline 9
- Fluoroquinolones: Ciprofloxacin 500-750 mg twice daily provides good Pasteurella coverage 9
- Trimethoprim-sulfamethoxazole plus metronidazole: Alternative option requiring additional anaerobic coverage 9
Severe or Disseminated Disease
- Rifampin, ciprofloxacin, or gentamicin: Greatest clinical efficacy observed with these agents 5
- Trimethoprim-sulfamethoxazole or clarithromycin: Also effective alternatives 5
Critical Management Pitfalls to Avoid
- Do not use first-generation cephalosporins (e.g., cephalexin) due to poor activity against P. multocida 2
- Do not use clindamycin as monotherapy for animal scratches due to inadequate Pasteurella coverage 9
- Do not proceed with elective surgery in the presence of active soft tissue infection, as this significantly increases risk of surgical site infection and systemic complications 2
Adjunctive Measures
- Wound care: Thoroughly cleanse with sterile normal saline to remove superficial debris 2, 9
- Elevation: Elevate affected limb to reduce swelling and accelerate healing 2, 9
- Tetanus prophylaxis: Update immunization if not current 2, 9
- Rabies assessment: Consider rabies risk for scratches from unknown or feral cats 9
Follow-Up and Monitoring
- Reassessment: Evaluate patient in 48-72 hours to ensure antibiotic efficacy and clinical improvement 2
- Complications to monitor: Septic arthritis, osteomyelitis, tendonitis, or disseminated disease with hepatosplenic involvement 2, 6
- Return precautions: Advise patients to return if signs of infection develop, including increasing pain, redness, swelling, purulent drainage, or fever 9
- Surgical rescheduling: Only reschedule elective procedures after complete resolution of erythema, swelling, and systemic symptoms, typically requiring 2-4 weeks 2
Special Populations
Diabetic Patients
- Extended treatment duration: 1-2 weeks for mild infections, up to 3-4 weeks if extensive or resolving slowly 9
- More aggressive approach: Required due to impaired immune response and delayed wound healing 9
- Optimal wound care: Proper cleansing, debridement of necrotic tissue, and off-loading of pressure 9
- Vascular assessment: Evaluate arterial supply and consider revascularization when indicated 9