Rochalimaea henselae infection. A new zoonosis with the domestic cat as reservoir.

To determine the reservoir and vector(s) for Rochalimaea henselae, a causative agent of bacillary angiomatosis (BA) and cat scratch disease, and to estimate the percentage of domestic cats with R henselae bacteremia in the Greater San Francisco Bay Region of Northern California. Hospital-based survey of patients diagnosed with BA who also had significant exposure to at least one pet cat, as well as a convenience sampling of pet or impounded cats for prevalence of Rochalimaea bacteremia. Community and university hospitals and clinics; veterinary clinics treating privately owned or impounded cats. Patients with or without human immunodeficiency virus infection, with biopsy-confirmed BA, who had prolonged exposure to pet cats prior to developing BA. Cultures and laboratory studies were performed on blood drawn from pet cats associated with patients with BA. The Rochalimaea species infecting pet cats and fleas and causing the BA lesions in human contacts of these cats was identified by culture, polymerase chain reaction-restriction fragment length polymorphism analysis, and DNA sequencing. The presence of R henselae bacteremia in pet cats was documented, and predictor variables for culture positivity were evaluated. Four patients diagnosed with BA who had prolonged contact with seven pet cats were identified. The Rochalimaea species causing BA lesions in these patients was determined to be R henselae. The seven pet cats were found to be bacteremic with R henselae; this bacterium was also detected in fleas taken from an infected cat by both direct culture and polymerase chain reaction. Blood samples were cultured from pet and impounded cats (N = 61) in the Greater San Francisco Bay Region, and R henselae was isolated from 41% (25/61) of these cats. We have documented that the domestic cat serves as a major persistent reservoir for R henselae, with prolonged, asymptomatic bacteremia from which humans, especially the immunocompromised, may acquire potentially serious infections. Antibiotic treatment of infected cats and control of flea infestation are potential strategies for decreasing human exposure to R henselae.