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Cat scratch disease

Background

Overview

Definition
CSD is a bacterial infection caused by Bartonella henselae, an aerobic Gram-negative bacillus.
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Pathophysiology
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.
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Epidemiology
In the US, 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.
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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).
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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.
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Guidelines

Key sources

The following summarized guidelines for the evaluation and management of cat scratch disease are prepared by our editorial team based on guidelines from the Infectious Diseases Society of America (IDSA 2014) and the American Academy of Family Physicians (AAFP 2011). ...
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Screening and diagnosis

Clinical presentation: as per AAFP 2011 guidelines, include CSD in the differential diagnosis of any patient with lymphadenopathy.
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  • Diagnostic criteria

Diagnostic investigations

Antibody testing: as per AAFP 2011 guidelines, a positive IgM test suggests acute disease, but production of IgM is brief.
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  • PCR testing

Diagnostic procedures

Lymph node biopsy: as per AAFP 2011 guidelines, 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.

Medical management

Indications for antibiotics: as per AAFP 2011 guidelines, consider avoiding routine antibiotic therapy in patients with self-limited disease.
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  • Antibiotic selection