What is the recommended treatment for a patient with cat scratch fever?

Treatment for Cat Scratch Fever

Azithromycin is the first-line treatment for cat scratch disease, dosed at 500 mg on day 1 followed by 250 mg daily for 4 additional days in patients >45 kg, or 10 mg/kg on day 1 and 5 mg/kg daily for 4 more days in patients <45 kg. 1

Treatment Algorithm

For Immunocompetent Patients with Typical Cat Scratch Disease

First-line therapy:

• Azithromycin is recommended by the American College of Physicians based on placebo-controlled evidence showing more rapid reduction in lymph node size 1
• This recommendation is supported by the only placebo-controlled study demonstrating clinical benefit 1, 2
• Most cases are self-limited and resolve within 1-6 months without treatment, but antibiotics accelerate recovery 1, 3

Alternative regimens if azithromycin is contraindicated:

• Doxycycline 100 mg twice daily for 10-14 days (CDC recommendation) 1, 4
• Erythromycin 500 mg four times daily 1
• For children <45 kg: doxycycline 2.2 mg/kg twice daily (max 100 mg/dose) for 10-14 days 4

For Severe or Disseminated Disease

When to treat aggressively:

• Extranodal or disseminated disease (occurs in ≤2% of cases) 1
• Hepatosplenic involvement 1, 5
• CNS involvement 1
• Any immunocompromised patient 1

Preferred regimens for severe disease:

• Gentamicin shows 73% efficacy with rapid response within 48 hours for hepatosplenic involvement 1, 5
• Doxycycline with or without rifampin is the CDC's treatment of choice for CNS bartonellosis and other severe infections 1

For Immunocompromised Patients (Especially HIV/AIDS)

Critical considerations:

• Up to 25% of culture-positive HIV patients with CD4+ <100 cells/µL may never develop antibodies 1
• Consider Bartonella in any HIV patient with unexplained fever and CD4+ <100 cells/µL 1
• Evaluate for bacillary angiomatosis (cutaneous vascular lesions mimicking Kaposi's sarcoma) 1

Treatment regimen:

• Erythromycin or doxycycline for more than 3 months for bacillary angiomatosis, peliosis hepatis, or CNS involvement 1
• Long-term suppression with erythromycin or doxycycline until CD4+ >200 cells/µL for >6 months to prevent relapse 1

Special Populations

Pregnant women:

• Erythromycin is the only safe option - tetracyclines (doxycycline) are completely contraindicated 1
• Use erythromycin for both acute treatment and long-term suppression if needed 1

Children:

• Same azithromycin regimen with weight-based dosing: 10 mg/kg day 1, then 5 mg/kg for 4 days if <45 kg 1, 6
• Fluoroquinolones should be used with extreme caution and only if no alternatives exist 1

Common Pitfalls and Caveats

Antibiotics to AVOID:

• Penicillins and first-generation cephalosporins have no in vivo activity and should never be used 1
• Quinolones and TMP-SMX have variable activity and inconsistent clinical response - not recommended by CDC 1
• Note: This contradicts older retrospective data showing ciprofloxacin efficacy 7, 5, but current CDC guidelines do not recommend fluoroquinolones 1

Diagnostic timing issues:

• Serologic testing may not show detectable antibodies until 6 weeks after acute infection 1
• Do not delay treatment waiting for serology in clinically suspected cases 1
• Do not test cats for Bartonella - this provides no benefit to diagnosis or management 1

When NOT to treat:

• Most immunocompetent patients with typical lymphadenopathy can be managed conservatively without antibiotics 3
• Lymphadenopathy generally resolves within 1-6 months spontaneously 1
• Treatment is primarily indicated for symptom acceleration, immunocompromised patients, or severe/disseminated disease 1

Monitoring and Follow-Up

• Suppuration occurs in approximately 10% of cases and may require drainage 1
• For immunocompromised patients on long-term suppression, continue until immune reconstitution (CD4+ >200 cells/µL for >6 months) 1
• Serial imaging may be needed for hepatosplenic involvement - lesions can take 4 months to resolve even with appropriate treatment 8