Bartonella infection in domestic dogs and wild carnivores from California: Seroepidemiology, clinical associations, and characterization of a new zoonosis

There are more than 20 known species or subspecies of Bartonella , several of which are recognized as emerging human and canine pathogens. To estimate the seroprevalence of antibodies against Bartonella spp. in dogs from northern California and identify potential risk factors and clinical signs associated with seropositivity, sera from 3,417 dogs were analyzed for antibodies against three Bartonella species. Approximately 3% of dogs were seropositive for ≥ 1 Bartonella spp. In a matched case-control study, herding dogs were more likely to be seropositive. Bartonella seropositive dogs were also more likely to be lame or have arthritis-related lameness, nasal discharge or epistaxis, or splenomegaly.;To investigate the epidemiology of Bartonella infection in an area with high risk of arthropod-borne diseases, samples were collected from dogs and gray foxes in a rural area in northern California. B. v. berkhoffii was isolated from 1 (0.5%, 1/182) dog and 5 (9.4%, 5/53) gray foxes. A novel Bartonella sp. was isolated from the blood of 3 (1.6%, 3/182) rural dogs and 22 (42%, 22/53) gray foxes. PCR-RFLP and sequence analysis indicated that the novel dog and fox isolates were most closely related to B. clarridgeiae. A recently described human isolate and a DNA sample from a case of fatal endocarditis in a dog from California were also analyzed. The dog, gray fox, and human sequences shared ≥ 99.5% similarity. Phylogenetic trees constructed showed that these canid and human bartonellae clustered together on a distinct branch close to B. clarridgeiae. This novel species of Bartonella , temporarily designated B. clarridgeiae-like, was also identified in 11 raccoons and 2 coyotes from California, as well as in a red fox from France.;Fifty-four (29%) dogs and 48 (89%) gray foxes had reciprocal IFA titers of ≥ 64 against Bartonella spp. Polytomous logistic regression models were used to assess the association of Bartonella IFA titer categories with potential risk factors and presence of other vector-borne agents in domestic dogs. There was a significant association between increased Bartonella IFA titers and increasing age. Dogs with high Bartonella IFA titers were also more likely to be D. immitis positive using a continuation ratio model.