A Prospective Study of Canine Infective Endocarditis in Northern California (1999–2001): Emergence of Bartonella as a Prevalent Etiologic Agent

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Abstract
A prospective study was performed (June 1999 to May 2001) to determine the incidence of infective endocarditis (IE) due toBartonellain dogs in northern California and to compare these patients with other dogs with IE. IE was diagnosed antemortem based on clinical signs and echocardiography in 18 dogs. The etiologic agent wasBartonellasp. in 5 dogs (28%) and was diagnosed by high seroreactivity toBartonella(titer>1:512; range, 1: 1,024‐1:4,096); and confirmed postmortem by positive polymerase chain reaction (PCR)‐restriction fragment length polymorphism (RFLP) from the infected valve and partial DNA sequencing of the citrate synthase gene (glt A).Conventional bacteria were causative agents in 7 dogs (39%). An etiologic agent was not identified in 6 dogs (33%).Bartonella vinsonii berkhoffii(n = 3),B clarridgeiae(n = 1), and aB clarridgeiae‐likeorganism (n = 1) were identified. Blood culture was positive only for the IE case due toB clarridgeiae.All dogs with IE due toBartonellawere also seroreactive toAnaplasma phagocytophilum.All dogs with IE due toBartonellahad lesions only on the aortic valve. Of the cases of IE not due toBartonella,31% involved the aortic valve, 61% the mitral valve, and 8% both valves. Dogs with mitral valve IE lived longer than all dogs with aortic valve IE (P= .004) and dogs with IE of the aortic valve due toBartonella(P= .002). In conclusion,Bartonellais a common cause of IE in dogs of northern California. A highBartonellaserologic titer (>1:512) is useful antemortem to diagnose aortic valve IE due toBartonella.