The diagnosis of canine bacterial endocarditis is usually based on appropriate clinical and echocardiographic findings or typical pathologic lesions (1
). The abnormalities we found were similar to those reported in dogs with bacterial endocarditis and endocarditis due to Bartonella spp., namely murmur (89%), fever (72%), leukocytosis (78%), hypoalbuminemia (67%), thrombocytopenia (56%), elevated liver enzymes (56%), lameness (43%), azotemia (33%), respiratory abnormalities (28%), and weakness and collapse (17%) (1
). One dog had clear echocardiographic evidence of endocarditis; the other had distinct lesions at necropsy not seen with echocardiography.
B. quintana was the most likely cause of endocarditis identified in our dogs. In the first dog, routine blood cultures were negative for other bacteria that cause endocarditis. PCR and sequencing, however, demonstrated DNA of B. quintana in the dog's blood at the time endocarditis was diagnosed. Although specialized blood cultures for Bartonella spp. were negative, these organisms have fastidious growth requirements, and blood cultures that use solid media have poor diagnostic sensitivity in both humans (9
) and dogs (1
The most useful techniques for detecting Bartonella endocarditis are immunohistochemical analysis of affected valves and PCR (1,5,8
). In case 2, the dog had typical histologic lesions of endocarditis that contained large numbers of Bartonella organisms, as shown by Warthin-Starry staining and immunohistochemical analysis. When the sequences of the fur gene were compared with those of Bartonella spp. that are known to cause endocarditis in dogs and humans, the sequencing results showed the Bartonella that infected the dog had highest homology (99%) with B. quintana and B. koehlerae. We did not have control DNA to test for B. washoensis, which has been described as an agent of endocarditis in a dog (4
) and myocarditis in a human (12
), but we regarded infection with this organism as unlikely because it has only been identified in the United States. Although we know of no specific reports of B. quintana in New Zealand, the organism is ubiquitous (13
) and is the most likely cause of the endocarditis in the dog we studied. We decided the organism was not B. koehlerae because it has not been reported in New Zealand or found in recent studies of its natural host (domestic cat) and vector (cat flea) in New Zealand (14–16
). Although the organism causes endocarditis in humans (17
), it does not appear to be pathogenic in cats, the natural host (18
Our description of B. quintana causing disease in the dog is the first report of the organism's pathogenicity in vertebrates other than humans, the natural reservoirs of the organism. Also, our report adds to the growing evidence that B. quintana can infect species other than humans. In recent reports, B. quintana was identified in a cat euthanized for medical reasons not related to infectious diseases (19
) and in an apparently healthy captive-bred cynomolgus monkey (Macaca fascicularis) (20
). B. quintana was first described as the agent of trench fever in soldiers in World War I. The organism causes a variety of clinical signs, including endocarditis, which is seen most commonly in immunocompetent, homeless men with a history of alcohol abuse (5
). Although the body louse is the traditional vector of B. quintana in humans, this parasite was not a likely source of infection for our dogs since it is host specific, and we found no evidence of infestation. Recent reports of B. quintana in persons with no history of body lice have suggested that other vectors may be involved. In France, a high percentages (17%) of C. felis contain DNA of B. quintana, which suggests that cat fleas might be vectors (21
). Although the dog from New Zealand had fleas, B. quintana has not been identified in C. felis in the country (15,16
). Another proposed vector is Ixodes pacificus (22
), but this tick does not occur in North Carolina or New Zealand. Further, ticks are very rarely found on dogs in New Zealand, where PCR studies on the only prevalent species, Haemaphysalis longicornis, have been negative for Bartonella spp (23
). The source of the B. quintana infections in the dogs we describe is unclear.
In summary, our study has shown B. quintana can infect dogs and cause endocarditis. Further studies are indicated to investigate the epidemiology of these infections.