Bartonella henselae Antibodies after Cat Bite1

To the Editor: Bartonella hense-lae is the causative agent of cat-scratch disease, which is the most common form of human bartonellosis (1). In immunocompromised patients, e.g., HIV-infected patients, B. henselae can give rise to longstanding fever, bacil-lary angiomatosis, and peliosis hepatitis (2). Domestic cats are the reservoir for B. henselae, and cat fl eas transmit the organism between cats (3). The seroprevalence and culture fi ndings of Bartonella spp. in cats have been shown to be low in Sweden (4,5) compared with warmer areas (6). Cat-scratch disease is most often spread from cats to humans by scratches, but other forms of transmission, including cat bites, have been suggested (7). To determine seroprevalence of antibodies against B. henselae in Sweden, we used data from a recently published prospective study of patients with infected cat bites (8). In addition to the information about bites, information about cat scratches was collected by retrospective review of the patients' medical records. Serum samples were taken during the pa-tient's fi rst visit to a hospital and at a follow-up visit about 2 weeks later. The study was approved by the local ethics committee. Immunoglobulin G against spe-cifi c Bartonella spp. was detected by the immunofl uorescence antibody test (1). Cell-cultivated antigens were prepared from the following strains: B. The cutoff values for a positive immunofl uores-cence antibody test result were chosen as >128 for B. henselae and B. graha-mii and >256 for B. elizabethae. The titers are expressed as the reciprocal of the end-point dilution. For controls, we also analyzed serum from 117 blood donors with these antigens. The χ 2 test was used for statistical analysis. We analyzed antibodies to Barto-nella spp. in serum from 71 patients (51 women and 20 men), median age 47 years (range 15–85 years). Only 11 patients had fever. Cat scratches were reported for 17 patients. A single serum sample was obtained from 37 of the 71 patients, and an additional convalescent phase sample was obtained from 34 patients after a median of 16 days (range 6–54 days). Antibodies against any B. hense-lae strain were found for 24/71 (34%) patients, against B. elizabethae for 9/71 (13%), and against B. graha-mii for 12/71 (17%). A total of 13/71 (18%) patients showed reactivity to B. henselae only. Antibodies to any Bartonella spp. were found for 28/71 (39%) of the patients. As many as 13/24 (54%) serum samples with an-tibodies against B. henselae …