What is the recommended treatment for cat scratch disease?

Treatment of Cat Scratch Disease

The recommended first-line treatment for cat scratch disease is azithromycin, with a dosage of 500 mg on day 1 followed by 250 mg for 4 additional days for patients >45 kg, and 10 mg/kg on day 1 and 5 mg/kg for 4 more days for patients <45 kg. 1

Clinical Presentation and Diagnosis

Cat scratch disease (CSD) is caused by Bartonella henselae, typically acquired from infected cats. The clinical presentation includes:

• Regional lymphadenopathy developing approximately 3 weeks after inoculation
• Papule or pustule at the scratch/bite site appearing 3-30 days after exposure
• Extranodal manifestations in approximately 2% of cases
• Suppurative nodes in about 10% of cases 1

Diagnosis is primarily made through:

• Serology (note: antibodies may not be detectable for up to 6 weeks post-infection)
• Histopathology using Warthin-Starry silver stain showing characteristic bacilli
• PCR for identification and speciation (though not widely accessible) 1

Treatment Algorithm

1. Uncomplicated CSD in Immunocompetent Patients

• First-line: Azithromycin 500 mg on day 1, then 250 mg daily for 4 days (for patients >45 kg) 1
• A randomized controlled trial demonstrated that azithromycin treatment resulted in significantly faster resolution of lymphadenopathy compared to placebo within the first 30 days 2
• Many uncomplicated cases resolve spontaneously without antibiotics 3, 4

2. Alternative Treatment Options

• Erythromycin 500 mg four times daily for 2 weeks to 2 months 1
• Doxycycline 100 mg twice daily for 2 weeks to 2 months 1
• For cat bite/scratch infections (not specifically CSD): Amoxicillin-clavulanate 875/125 mg twice daily 1

3. Special Populations

Immunocompromised Patients:

• Longer treatment courses (>3 months) are recommended 1
• Consider combination therapy with azithromycin and rifampicin for disseminated disease 5

CNS Involvement:

• Doxycycline with or without rifampin is recommended 1

Diabetic Patients:

• Amoxicillin-clavulanate 875/125 mg orally twice daily for 5-7 days
• Doxycycline 100 mg twice daily for penicillin-allergic patients 1

Follow-up and Monitoring

• Schedule follow-up appointments to assess symptom resolution
• Be aware that lymphadenopathy may persist for 1-6 months despite appropriate treatment
• Clinical reassessment within 24-48 hours is necessary for patients with worsening lymphangitis and edema 1

Important Clinical Considerations

1. Atypical Presentations: Up to 25% of cases may present atypically with ocular involvement, encephalopathy, granulomatous hepatitis, hepatosplenic infection, endocarditis, or osteomyelitis 4

2. Prevention in High-Risk Individuals: Immunocompromised patients should:

   • Avoid rough play with cats
   • Keep cats' nails trimmed
   • Wash hands thoroughly after handling cats
   • Consider avoiding cat ownership or adopt cats over 1 year of age
   • Implement proper flea control for cats 1

3. Treatment Efficacy: While several antibiotics show in vitro activity against B. henselae, greatest clinical efficacy has been observed with rifampin, ciprofloxacin, gentamicin, trimethoprim-sulfamethoxazole, clarithromycin, and azithromycin 3

4. Seasonal Variation: Higher rates of infection are reported in autumn and winter in temperate climates, attributed to seasonal breeding of domestic cats 4