Cat‐Scratch Disease

Published on 10/06/2015 by admin

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Last modified 22/04/2025

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Cat-Scratch Disease

Mary T. Caserta, MD

Basic Information

Definition

Cat-scratch disease (CSD) is a subacute to chronic regional lymphadenitis syndrome that occurs after cutaneous, ocular, or mucous membrane inoculation in a person who has contact with a cat.

Synonym

Cat-scratch fever

ICD-9-CM Code

078.3 Cat-scratch disease

Epidemiology & Demographics

• There are 22,000 to 24,000 cases per year of CSD in the United States (9.3 per 100,000 population).
• Approximately 2000 patients are hospitalized per year in the United States (0.77 to 0.86 per 100,000 hospital discharges).
• Distribution is worldwide, but it is most prevalent in warm and humid climates.
• The incidence is more common in fall and winter (60% of cases identified from September to January).
• 50% of patients are younger than 15 years of age.
• A zoonotic disease of cats, especially kittens. Asymptomatic cats may be persistently bacteremic with the causative organism for long periods of time.
• Fleas maintain the zoonotic infection among cats.

Clinical Presentation

• A papule or pustule at the site of the scratch precedes the appearance of regional lymphadenopathy by 1 to 6 weeks in 60% to 93% of patients.
• Gradual enlargement of a single, tender lymph node is observed in 80% of patients (20% have multiple node enlargements clinically, but up to 90% have multiple enlarged nodes in one site by ultrasonography).
• Most nodes (80%) are 1 to 5 cm in size and appear on the axilla, head, neck, or upper extremity.
• A papule or pustule at a distal site is drained by the enlarged node.
• Fever is usually absent or low-grade (10% with temperature higher than 39°C).
• From 10% to 30% of nodes spontaneously suppurate, but most resolve over 2 to 6 months.
• Atypical presentations include encephalopathy with seizures, hepatosplenic granulomas, multiple bone lesions, Parinaud’s oculoglandular syndrome (conjunctival granuloma with ipsilateral preauricular adenopathy), neuroretinitis, endocarditis, or a prolonged febrile illness, seen in 10% to 25% of infections.
• Patients may have constitutional symptoms, including fatigue (30%), headache (14%), anorexia or weight loss (15%), or sore throat (9%) with regional lymphadenitis.
• Immunocompromised children may develop more severe manifestations of infection and should always receive antimicrobial treatment.

Etiology

• Bartonella henselae, a fastidious, pleomorphic, gram-negative bacillus

Diagnosis

Differential Diagnosis

• Bacterial adenitis
• Infectious mononucleosis
• Toxoplasmosis
• Mycobacteria infection
• Cytomegalovirus infection
• Lymphoma malignancy
• Histoplasmosis

Workup

Initially, a clinical diagnosis is based on appropriate symptoms and a history of exposure to a cat or kitten and confirmed by serology.

Laboratory Tests

• Serologic diagnosis is the test of choice (indirect immunofluorescence assay or enzyme immunoassay) with a positive titer of more than 1:64 for immunoglobulin G (IgG) or more than 1:20 for immunoglobulin M (IgM).
• Lymph node biopsy reveals scattered granulomas with necrosis and abscess formation.
• Culture and Gram stain of B. henselae are technically very difficult.
• Polymerase chain reaction test is available at reference laboratories.

Imaging Studies

• Ultrasonography demonstrates enlarged hypoechoic lymph nodes with increased vascularity on Doppler images.
• May also see hypoechoic nodules in the liver or spleen by ultrasonography in approximately 30% of patients with CSD without abdominal discomfort.

Treatment

Nonpharmacologic Therapy

• Local care, including the application of moist heat to an enlarged node or nodes

Acute General Rx

• Azithromycin 10 mg kg on day 1 then 5 mg kg on days 2 through 5 decreases lymph node size faster than placebo.

Chronic Rx

• A few patients require needle aspiration for drainage and relief of symptoms or complete removal of the involved node or nodes.

Disposition

• Gradual and spontaneous resolution of lymphadenopathy over 2 to 6 months is the rule.

Referral

• Children can be cared for by their primary care pediatrician or a pediatric infectious diseases expert.

Pearls & Considerations

Comments

• Examine the web spaces between the fingers for an inoculation papule in a patient with lymphadenopathy of the upper extremity.
• Always consider CSD in the differential diagnosis of seizures, encephalopathy, or combative behavior and inquire about a history of cat contact while examining the patient closely for an inoculation papule or lymphadenopathy.
• Remember to think of atypical CSD in a patient with fever of unknown origin.

Prevention

• Avoidance of scratches or bites from cats and kittens will prevent infection.

Patient Family Education

• Approximately 28% of cats have evidence of past or present infection with B. henselae.
• Cat infection with B. henselae is correlated with fleas.
• There is no known person-to-person transmission of CSD.

Suggested Readings

Bass JW, et al. The expanding spectrum of Bartonella infections: II, cat-scratch disease. Pediatr Infect Dis J. 1997;16:163.

Bass JW, et al. Prospective randomized double blind placebo-controlled evaluation of azithromycin for treatment of cat-scratch disease. Pediatr Infect Dis J. 1998;17:447.

Carithers HA. Cat-scratch disease: an overview based on a study of 1,200 patients. Am J Dis Child. 1985;139:1124.

Garcia CJ, et al. Regional lymphadenopathy in cat-scratch disease: ultrasonographic findings. Pediatr Radiol. 2000;30:640.

Jackson LA, et al. Cat scratch disease in the United States: an analysis of three national databases. Am J Public Health. 1993;12:1707.

Metzkor-Cotter 2003 Metzkor-Cotter E, et al. Long-term serological analysis and clinical follow-up of patients with cat scratch disease. Clin Infect Dis. 2003;37:1149.

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