INTRODUCTION

Cat scratch disease (CSD) (La Maladie de Griffe de Chat) was first described in 1950 by Rene Debré. Its cause remained a mystery until the late 20th century, when the polymerase chain reaction (PCR) was applied to amplification and sequencing of 16SRNA genes as a method of identifying organisms that had not been successfully cultured. In 1992, David Relman and co-workers used this technique to identify the agent of CSD, bacillary angiomatosis and parenchymal bacillary peliosis (BAP). The causative organism, a small gram-negative bacillus, belongs to the α2 subdivision of proteobacteria and is closely related to the agent of trench fever and to Brucella sp.

First named Rochalimaea henselae, the organism was subsequently grouped within the family Bartonellaceae, along with a number of other mammalian bacterial parasites, including the agents of trench fever, Bartonella quintana (formerly Rochalimaea quintana) and Carrión's disease, Bartonella bacilliformis. These organisms, and probably others of the genus, share the ability to invade vascular endothelial cells, bone marrow erythroblasts, and mature erythrocytes. Bartonella henselae, B. quintana, and B. bacilliformis also share the ability to induce macrophage-mediated secretion of proinflammatory cytokines and vascular endothelial cell growth factor (VEGF) and to suppress apoptosis of vascular endothelial cells. These virulence factors are implicated in the proliferative vascular lesions seen with bartonella infections in immunocompromised patients and in the ability of these organisms to cause prolonged bacteremia in nonhuman reservoir species and humans.