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Bartonella are Gram-negative bacilli, with the remarkable capacity for intraerythrocyte persistence and the production of bacteremia. Until the 1980s, Bartonella were felt to only cause a rather exotic illness, Carrion disease. Since the description of a peculiar vascular proliferation in patients infected with Human Immunodeficiency Virus (HIV) infection, the number of identified Bartonella sp. has been rapidly expanding. The genus includes three important species that are human pathogens: (1) Bartonella henselae, the cause of most cases of cat-scratch disease (CSD) as well as some cases of bacillary angiomatosis (BA), hepatic and splenic peliosis (cystic blood-filled spaces in hepatic lobules or the splenic parenchyma), and endocarditis; (2) Bartonella quintana, the cause of trench fever, urban trench fever, BA, and endocarditis; and (3) Bartonella bacilliformis, the cause of Carrion disease and its eruptive phase known as verruga peruana (VP). Other potential human pathogens are Bartonella elizabethae and Bartonella vinsonii, which cause endocarditis, Bartonella grahamii, a cause of neuroretinitis, and Bartonella washoesis, which causes myocarditis (Table 182-1).1 Infections caused by most Bartonella are associated with arthropod vectors that may simultaneously carry several species. Adaptation to specific vectors and reservoirs seems to be a common strategy of Bartonellae for transmission and host diversity. At least one mammal host is known for every one of the Bartonella species identified to date.2 Human beings are the exclusive hosts for B. bacilliformis and B. quintana, whereas in the case of B. henselae, the cat is the host of choice with man being a more accidental host. Asymptomatic bacteremia rates in primary vertebrate (reservoir) hosts may exceed 50%. This suggests high prevalence of infection and prolonged and persistent bacteremia as characteristics of Bartonella infection. The extent of disease caused by B. henselae will depend on the integrity of the immune system: if the person affected is immune competent, the clinical presentation can be a lymphocutaneous syndrome. If the person affected is immune deficient, the disease will be systemic and very similar to that seen in Carrion disease. 3
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