What is the recommended treatment for cat scratch fever?

Treatment of Cat Scratch Fever

Azithromycin is the first-line antibiotic 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

When to Treat vs. Observe

Most immunocompetent patients with uncomplicated cat scratch disease do not require antibiotics, as the condition is self-limited with lymphadenopathy resolving within 1-6 months. 2, 3 However, treatment is indicated in specific scenarios:

• Immunocompromised patients (especially HIV with CD4+ <100 cells/µL) require treatment due to risk of disseminated disease including bacillary angiomatosis, peliosis hepatis, and CNS involvement 1
• Extranodal or disseminated disease (hepatosplenic involvement, neuroretinitis, encephalopathy, endocarditis) requires antibiotic therapy 1, 2
• Severe or persistent symptoms warrant treatment to accelerate recovery 1, 3

First-Line Treatment Algorithm

Standard Therapy

• Azithromycin is supported by placebo-controlled evidence showing more rapid reduction in lymph node size 1, 2
• Dosing for adults/children >45 kg: 500 mg day 1, then 250 mg daily × 4 days 1, 4
• Dosing for children <45 kg: 10 mg/kg day 1, then 5 mg/kg daily × 4 days 1, 4

Alternative Regimens (if azithromycin contraindicated)

• Doxycycline 100 mg twice daily for 10-14 days 1, 5
• Erythromycin 500 mg four times daily 1

Special Populations and Severe Disease

Immunocompromised Patients (HIV/AIDS)

• Erythromycin or doxycycline for >3 months for bacillary angiomatosis, peliosis hepatis, or CNS involvement 1
• Doxycycline with or without rifampin is preferred for CNS bartonellosis and severe infections 1
• Continue suppressive therapy until CD4+ >200 cells/µL for >6 months 1
• Critical caveat: Up to 25% of HIV patients with CD4+ <100 cells/µL may never develop antibodies despite active infection 1

Pregnant Women

• Erythromycin is the only safe option—tetracyclines (doxycycline) are absolutely contraindicated 6, 1
• Use erythromycin for both acute treatment and long-term suppression if needed 6, 1

Children

• Weight-based azithromycin dosing as above 1, 4
• Fluoroquinolones should be used with extreme caution and only if no alternatives exist 1

Severe Hepatosplenic Disease

• Gentamicin has shown 73% efficacy with rapid response within 48 hours, though evidence quality is lower than azithromycin 1, 7
• Extended treatment (5 weeks of azithromycin) may be needed for disseminated disease with hepatosplenic micro-abscesses 8

Antibiotics That Do NOT Work

Avoid these agents as they have no clinical efficacy or are contraindicated:

• Penicillins and first-generation cephalosporins have no in vivo activity 1
• Quinolones and TMP-SMX have variable activity and inconsistent clinical response 1

Prevention of Recurrence

• Long-term suppression with erythromycin or doxycycline should be considered for patients with relapse or reinfection 6, 1
• This is particularly important in immunocompromised patients until immune reconstitution occurs 1

Diagnostic Pitfalls

• Serologic testing may not show detectable antibodies until 6 weeks after acute infection in immunocompetent patients 1
• In advanced HIV (CD4+ <100 cells/µL), 25% of culture-positive patients may never develop antibodies—do not rely on serology alone 1
• Consider Bartonella in any HIV patient with unexplained fever and CD4+ <100 cells/µL 1
• Do not test cats for Bartonella infection—this provides no benefit to diagnosis or management 4

Prevention Measures

For severely immunosuppressed persons considering cat ownership:

• Adopt cats >1 year old in good health 6, 1
• Avoid rough play and situations where scratches are likely 6, 1
• Promptly wash any cat-associated wounds 6, 1
• Implement comprehensive flea control 6, 1
• Do not allow cats to lick open wounds 6, 1