Treatment of 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
When to Treat vs. Observe
Most cases of cat scratch disease in immunocompetent patients are self-limited and resolve within 1-6 months without antibiotics 1, 2. However, treatment is specifically indicated for:
- Immunocompromised patients 1
- Extranodal or disseminated disease 1
- Severe or persistent lymphadenopathy causing significant symptoms 1
- Patients who desire faster resolution of lymph node swelling 1
The evidence supporting azithromycin comes from a placebo-controlled study demonstrating more rapid reduction in lymph node size compared to placebo, though the disease ultimately resolves without treatment in most immunocompetent individuals 1, 2.
Alternative Antibiotic Options
If azithromycin is contraindicated or unavailable:
- Doxycycline 100 mg twice daily is the preferred alternative 1
- Erythromycin 500 mg four times daily is another alternative 1
- Rifampin, ciprofloxacin, gentamicin, trimethoprim-sulfamethoxazole, and clarithromycin have shown clinical efficacy in various studies 2, 3
Critical caveat: Penicillins and first-generation cephalosporins have no in vivo activity against Bartonella and should never be used 1. Quinolones and TMP-SMX have variable activity and inconsistent clinical response 1.
Special Populations Requiring Modified Treatment
Immunocompromised Patients (HIV/AIDS, CD4+ <100 cells/µL)
These patients require extended therapy for more than 3 months with erythromycin or doxycycline for bacillary angiomatosis, peliosis hepatis, or CNS involvement 1. Doxycycline with or without rifampin is the treatment of choice for CNS bartonellosis and other severe infections 1. Consider Bartonella in any HIV patient with unexplained fever and CD4+ <100 cells/µL 1.
Pregnant Women
Erythromycin is the preferred agent as tetracyclines are contraindicated during pregnancy 1. This applies both for acute treatment and long-term suppression if needed 1.
Patients with Relapse or Reinfection
Long-term suppression with erythromycin or doxycycline should be considered 1. For pregnant women requiring suppression, use erythromycin 1.
Immunosuppressed Patients on Immunomodulators
A case report demonstrated that persistent cat scratch disease in a patient on mycophenolate and prednisone required 9 months of antibiotics and ultimately surgical excision of affected nodes 4. Surgical excision should be considered for disease persisting beyond 16 weeks despite appropriate antibiotic therapy 4.
Diagnostic Pitfalls That Affect Treatment Decisions
- Serologic testing may not show detectable antibodies until 6 weeks after acute infection 1
- In advanced HIV infection (CD4+ <100 cells/µL), up to 25% of culture-positive patients may never develop antibodies 1
- Do not test cats for Bartonella infection—this provides no benefit to diagnosis or management 1
- Bacillary angiomatosis lesions can be clinically indistinguishable from Kaposi's sarcoma and may require biopsy 1
Treatment Duration
- Standard immunocompetent patients: 5 days total (azithromycin protocol) 1
- Immunocompromised with severe disease: More than 3 months 1
- Persistent disease despite treatment: Consider surgical excision if no improvement after 16 weeks 4
Prevention Measures
To prevent initial infection or reinfection 1:
- Choose cats >1 year old in good health
- Avoid rough play and situations where scratches are likely
- Promptly wash any cat-associated wounds
- Implement comprehensive flea control for cats
- Do not allow cats to lick open wounds
- Severely immunosuppressed persons should carefully consider risks of cat ownership