There are about 22,000 cases of cat scratch disease (CSD) in the U.S. each year. Cat scratch disease occurs most commonly in children, with 57-80% of cases in individuals <21 years of age (highest age-specific incidence is in children <10 years of age).

Cat scratch disease is manifest most commonly as a series of papules and pustules around a cat scratch (59-93% of patients), or much less commonly a cat bite. These papules and pustules typically develop within a few days of the scratch and the scratch itself may persist as a non-healing wound. This stage of disease is followed 7-50 days later by the development of a regional lymphadenopathy (>90% of patients) in nodes proximal to the scratch, most commonly the lymph nodes of the axilla, neck or groin and sometimes affecting multiple nodes. (The nodes only rarely suppurate/abscess.)

• Patients may also have fever (32-60% of patients), headache and malaise (13-29% of patients), but most patients generally feel well.
• Histologically, the nodes are characterized by necrotizing, granulomatous inflammation and micro-abscess formation.
  • Patients have historically undergone surgical biopsy of the enlarged LN to rule out lymphoid neoplasia.
• Patients with CSD occasionally develop lesions in other locations that present more serious health concerns, e.g., the recent case of a patient with an inflammatory mass lesion of the optic nerve head that progressed to more generalized neuroretinitis.
• Bartonella infections in humans are diagnosed serologically (IFA, ELISA assays) based upon either a single high IgG titer, a 4-fold rise in IgG titers or a positive IgM titer, or by culture or PCR detection of the organism.

Antibiotic therapy?

The value of antibiotics in the treatment of uncomplicated CSD is unclear. Most feel that antibiotics do not significantly alter the course of disease (lymphadenopathy typically regresses spontaneously in 2-6 months), although a recent study suggests that the drug azithromycin, which penetrates lymph node tissue and concentrates intracellularly, may be effective in reducing the size of the affected node(s).

CSD as an occupational hazard for veterinarians?:
As one might expect, a recent survey conducted at a veterinary conference in Ohio suggested that the rate of CSD in veterinarians (6%) is higher than that in the general public.

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