Bartonella endocarditis: a pathology shared by animal reservoirs and patients

Bartonellae were first recognized to cause endocarditis in humans in 1993 when cases caused by Bartonella quintana, B. elizabethae, and B. henselae were reported. Since the first isolation of Bartonella vinsonii subspecies berkhoffii from a dog with endocarditis, this organism has emerged as an important pathogen in dogs and an emerging pathogen in people. Subsequently, four types of B. vinsonii subsp. berkhoffii have been described, all of which have been associated with endocarditis in dogs. A limited number of dog endocarditis cases have also been associated with B. clarridgeiae, B. washoensis, B. quintana, and B. rochalimae. The second canine B. clarridgeiae endocarditis case is presented. The clinical and pathological characteristics of Bartonella endocarditis in dogs are similar to disease observed in humans, more often affecting the aortic valve, presenting with highly vegetative lesions with accompanying calcification, and in most instances high antibody titers. Pathological features in dogs include a combination of fibrosis, mineralization, endothelial proliferation, and neovascularization with variable inflammation. Endocarditis has also been described in animal species, which are the natural reservoir of specific Bartonella species, once thought to be solely healthy carriers of these pathogens. A few Bartonella endocarditis cases, including B. henselae, have been reported in cats in the USA and Australia. The second case of B. henselae type Houston I identified in the USA is presented. Furthermore, two cases of B. bovis endocarditis were recently described in adult cows from France. Finally, on-going investigation of valvular endocarditis in free-ranging Alaskan sea otters suggests the involvement of Bartonella species.