Guideline sources The following summarized guidelines for the evaluation and management of cat-scratch disease (CSD) are prepared by our editorial team based on guidelines from the Infectious Diseases Society of America (IDSA 2014) and the American Association of Family Physicians (AAFP 2011). 1 1 1 1 1 2 2 3 Definition CSD is a bacterial infection caused by Bartonella henselae, an aerobic Gram-negative bacillus. 1 Epidemiology CSD is caused by Bartonella henselae, an aerobic Gram-negative bacillus. Bartonella henselae can infect feline erythrocytes and fleas, which can contaminate saliva and then be introduced into humans through biting and clawing by cats. The cat flea, Ctenocephalides felis, is the vector responsible for horizontal transmission of the disease from cat to cat, and its bite can also infect humans. In addition, tick bites may transmit the bacterium to humans. 1 1 Pathophysiology In the United States, the annual incidence of CSD is estimated at 4.5 cases per 100,000 person- years, while the incidence of CSD requiring hospitalization is estimated at 0.19 cases per 100,000 person-years. 3 https://web.pathway.md/diseases/reciAU0PATJg5nQ9x 1/3 6/29/23, 3:45 AM Cat-scratch disease Pathway Disease course In the classic disease course, a papule or pustule develops 3-30 days following a scratch or a bite, and regional lymphadenopathy develops about 3 weeks after inoculation. Suppurative lymphadenopathy may develop in 10% of cases. Less than 2% of patients develop extranodal disease (for example CNS, liver, spleen, bone, and lung involvement). 2 Prognosis and risk of recurrence In most patients, especially children, the disease is self-limited, and resolves without specific treatment. In immunosuppressed patients, Bartonella henselae can lead to bacillary angiomatosis and bacillary peliosis, which have high rates of relapse and require prolonged antibiotics. 1 Guidelines 1. Screening and diagnosis Clinical presentation: include CSD in the differential diagnosis of any patient with lymphadenopathy. B Diagnostic criteria: diagnose CSD in patients with compatible symptoms, a history of cat exposure, and antibodies to Bartonella henselae. B 2. Diagnostic investigations Antibody testing: A positive IgM test suggests acute disease, but production of IgM is brief. Show 2 more PCR testing: PCR can detect different Bartonella species; specificity is very high, but the sensitivity is lower than with serology. 3. Diagnostic procedures Lymph node biopsy: lymph node biopsy is not indicated for most patients; however, it is appropriate in patients whose lymph nodes fail to involute and in whom diagnosis is uncertain. 4. Medical management Indications for antibiotics: consider avoiding routine antibiotic therapy in patients with self- limited disease. D Antibiotic selection: As per IDSA 2014 guidelines: Administer azithromycin for cat scratch disease, according to the following dosing protocol: https://web.pathway.md/diseases/reciAU0PATJg5nQ9x 2/3 6/29/23, 3:45 AM Cat-scratch disease Pathway 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. B Administer one of the following regimens for the treatment of patients with bacillary angiomatosis: erythromycin 500 mg QID, for 2 weeks to 2 months doxycycline 100 mg BID, for 2 weeks to 2 months. B As per AAFP 2011 guidelines, consider using azithromycin as the first-line antibiotic in patients in whom a decision to treat is made, as it appears to be effective at reducing the duration of lymphadenopathy. C Clinical findings Symptoms Past medical history Abdominal pain Bacterial infection Arthralgia Cancer Chills Diabetes mellitus Fatigue Immunocompromising condition Fever Ocular exam Headache Pain Uveitis Swollen lymph nodes Integument exam Social history Rash Exposure to cat scratch Lymphatic exam Unilateral lymphadenopathy References 1. Klotz S, Ianas V, Elliott S. Cat-scratch Disease. Am Fam Physician. 2011 Jan 15;83 2 152 5. Open 2. Stevens DL, Bisno AL, Chambers HF et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014 Jul 15;59 2):e10 52. Open 3. Nelson C, Saha S, Mead P. Cat-Scratch Disease in the United States, 2005 2013. Emerg Infect Dis. 2016 Oct;22 10 1741 6. Open https://web.pathway.md/diseases/reciAU0PATJg5nQ9x 3/3