Prevalence of antibodies to Bartonella henselae in patients with suspected cat scratch disease (CSD) in Italy

Cat scratch disease (CSD) is a relatively new diagnosed illness with clinical signs of self-limiting regional lymphadenopathy accompanied by symptoms of fever and malaise, to encephalopathy and neuropathy, occurring after a cat scratch or flea bite. Bartonella henselae is now accepted as the etiologic agent of CSD. From January 1994 to September 1998, 412 patients were evaluated for suspect CSD in Italy. Sera were tested for antibodies to B. henselae by a commercially available indirect immunofluorescent assay (IFA), based on B. henselae-infected Vero-cells as the antigen substrate. Of the 412 patients, 26 (6.3%) were considered positive having titers of immunoglobulin G (IgG) to B. henselae of 64 or higher. In these patients CSD was indeed confirmed by either histopathologic examination of lymph nodes biopsy or fourfold raise in antibody titers. Nevertheless, sera were tested by IFA for Afipia felis and one showed a double reactivity to B. henselae and A. felis. Finally, three sera, negative to B. henselae serology, were positive to A. felis. Three hundred and eighty-six patients received alternative diagnoses. One hundred and twenty-five serum samples from control subjects were negative by IFA for either B. henselae or A. felis. Moreover, a cross-reactivity with sera from patients affected by other diseases was not observed. Our study shows that the ascertained cases of CSD are etiologically determined by B. henselae, IFA assay is confirmed as a useful tool in the laboratory diagnosis and, over a 5 years period of study, the incidence of CSD in Italy has been low.