What is the treatment for cat scratch disease?

Treatment of Cat Scratch Disease

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

Overview of Cat Scratch Disease

Cat scratch disease (CSD) is an infection caused by Bartonella henselae, a fastidious gram-negative bacillus acquired from exposure to an infected kitten or cat. The most common manifestation is lymphadenopathy, with the following clinical course:

• A papule or pustule develops 3-30 days after a cat scratch or bite
• Regional lymphadenopathy occurs approximately 3 weeks after inoculation
• Lymphadenopathy generally resolves within 1-6 months
• In about 10% of cases, the lymph nodes may suppurate
• Extranodal disease (CNS, liver, spleen, bone, lung) develops in ≤2% of cases 1

Treatment Recommendations

For Typical Cat Scratch Disease:

1. First-line treatment:

   • Azithromycin according to the following protocol 1:
     • Patients >45 kg: 500 mg on day 1 followed by 250 mg for 4 additional days
     • Patients <45 kg: 10 mg/kg on day 1 and 5 mg/kg for 4 more days

2. Alternative treatments:

   • Many uncomplicated cases are self-limiting and may not require antibiotic therapy 2
   • If azithromycin cannot be used, consider:
     • Rifampin (87% efficacy in observational studies) 3
     • Ciprofloxacin (84% efficacy in observational studies) 3
     • Trimethoprim-sulfamethoxazole (58% efficacy in observational studies) 3

For Special Situations:

1. Bacillary angiomatosis (immunocompromised patients, especially with AIDS):

   • Erythromycin 500 mg four times daily OR
   • Doxycycline 100 mg twice daily
   • Treatment duration: 2 weeks to 2 months 1

2. Cat scratch cellulitis in diabetic patients:

   • Amoxicillin-clavulanate 875/125 mg orally twice daily for 5-7 days 4
   • For penicillin-allergic patients: doxycycline 100 mg twice daily 4

Evidence for Treatment Efficacy

The recommendation for azithromycin is based on a double-blind, placebo-controlled study that showed lymph node size regressed by 80% at 30 days more frequently in azithromycin-treated patients compared to placebo (P = .02) 1. This represents the highest quality evidence available for CSD treatment.

Treatment of cat scratch disease with antimicrobial agents has generally had variable results. The majority of cases in immunocompetent hosts are self-limited and may not require antibiotic therapy 2, 5.

Prevention Recommendations

For HIV-infected persons or other immunocompromised individuals who are at higher risk for severe disease:

1. Consider the risks of cat ownership, particularly with severe immunosuppression 1
2. If acquiring a cat, adopt or purchase an animal aged >1 year in good health 1
3. Avoid rough play with cats and situations where scratches are likely 1
4. Wash any cat-associated wound promptly 1
5. Implement flea control for cats 1
6. Do not allow cats to lick open wounds or cuts 1

Potential Pitfalls and Caveats

• Diagnostic challenges: B. henselae is difficult to culture, making diagnosis challenging. Serologic testing or PCR are considered the best methods of detection 6
• Treatment duration: While azithromycin is typically given for 5 days, longer courses may be needed for complicated or disseminated disease
• Monitoring: Follow patients for resolution of lymphadenopathy, which may take weeks to months despite appropriate therapy
• Atypical presentations: Up to 25% of cases may present atypically with ocular involvement, encephalopathy, hepatitis, or other manifestations, which may require more aggressive or prolonged therapy 6
• Immunocompromised patients: These individuals require more aggressive treatment and longer duration of therapy, with close monitoring for complications 5

By following these evidence-based recommendations, most patients with cat scratch disease will experience resolution of symptoms with minimal complications.