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Cat scratch disease
Acknowledgments
The authors thank Bryan A. Selkin and George J. Murakawa for writing the previous version of this chapter.
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Cat scratch disease (CSD) is a benign, usually self-limited disease caused by Bartonella henselae (formerly Rochalimaea henselae ), a Gram-negative pleomorphic rod. The primary lesion consists of a 0.5- to 1-cm papule or pustule, which may undergo ulceration, and adjacent unilateral lymphadenopathy is the hallmark of the disease. Atypical manifestations, including retinitis/neuroretinitis, Parinaud syndrome (granulomatous conjunctivitis and preauricular adenopathy), neuritis, encephalitis, hepatosplenic disease, osteomyelitis, erythema nodosum, and endocarditis, develops in 5%–20% of patients with the disease.
Atypical manifestations of cat-scratch disease, United States, 2005–2014
Nawrocki C, Max R, Marzec N, et al. Emerg Infect Dis. 2020; 26: 1438–46.
Using US nationwide insurance claims data, authors identified and characterized 224 atypical cases of cat scratch disease during 2005–2014 and estimated an average annual incidence of 0.7 cases/100,000 population. Ocular (48.7%), hepatosplenic (24.6%), and neurologic (13.8%) manifestations were common. Atypical cat scratch occurred most often in females 10–14 years of age.
Management Strategy
As there is a paucity of data showing a clear benefit of antimicrobial therapy in the treatment of patients with mild-to-moderate CSD, these patients should be managed with conservative, symptomatic treatment . The lymphadenopathy associated with CSD is self-limiting and resolves in 2–4 months; therefore, most patients can be managed with observation until involution of the node.
For patients with systemic symptoms and/or complications, antibiotic therapy should be instituted. Azithromycin (500 mg on day 1, followed by 250 mg on days 2–5) is the only antibiotic that has been shown in a double-blind, placebo-controlled evaluation to be beneficial to immunocompetent patients with CSD. In a retrospective analysis of 202 patients with CSD who had been on at least 3 days of antimicrobial therapy, only four antibiotics ( rifampin, ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole ) provided clinical benefit.
In immunosuppressed patients, infection with the CSD bacillus can produce a spectrum of disease, from classic CSD to bacillary angiomatosis, peliosis, or septicemia (see Chapter 21 , Bacillary angiomatosis). Antimicrobial treatment for such patients is beneficial and clearly indicated. Lesions and symptoms respond rapidly to erythromycin 500 mg four times daily or doxycycline 100 mg twice daily. In patients with AIDS, therapy should be administered for at least 3 months.
Of note, B. henselae has rarely been isolated from patients with CSD; however, patients who are immunosuppressed may be culture positive. A single dose of oral antibiotics will rapidly sterilize blood and lesional cultures.
Specific Investigations
CSD may be diagnosed presumptively in patients with typical signs and symptoms and a compatible exposure history. The Bartonella species are difficult to culture, and serology is the best initial test and can be performed by indirect fluorescent assay or enzyme-linked immunosorbent assay. Although more sensitive than culture, serologic tests lack specificity because many asymptomatic persons may have positive serology because of previous (often asymptomatic) exposure. B. henselae DNA may be detected by PCR or culture of lymph node aspirates or blood. Lymph node biopsy is not indicated routinely but should be considered if the diagnosis is unclear.
Evaluation of sensitivity, specificity and cross-reactivity in Bartonella henselae serology
Vermeulen MJ, Verbakel H, Notermans DW, et al. J Med Microbiol 2010; 59: 743–5.
The combined use of (Houston strain) indirect fluorescence antibody assay (IFA), IgM, and IgG improves sensitivity with significant reduction of specificity. Erroneous diagnosis of CSD can have a major impact for the patient, so IgG results must be interpreted with caution.
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