Bartonella vinsonii, subspecies berkhoffii, has been reported to cause cardiac arrhythmia, endocarditis, myocarditis, and granulomatous lymphadenitis and rhinitis in dogs. Bartonella henselae also has been reported to cause liver disease (peliosis hepatitis) in dogs. While vectors have not been identified for Bartonella spp., ticks are believed to be likely vectors. There is a high rate of co-infection in dogs with ehrlichiosis, babesiosis and bartonellosis. Any dog being treated for Babesia spp. or Ehrlichia spp. infection and not responding completely should be tested for Bartonella spp. infection. Immunosuppression results from bartonellosis, and this may impair ability of the dog to clear concurrent infections.

Of about 700 serum samples screened by Dr. Breitschwerdt's laboratory, 90 (11%) were seropositive for Bartonella spp., which is higher than the previously noted 3% rate. Of these 90, 30 dogs had no other antibodies against infectious agents and 24 had complete medical records. Among these 24 dogs, 30% had dermatologic changes of erosion/scabbing of ear tips and leukocytoclastic vasculitis on biopsy. Some dogs had joint pain, and 20% had uveitis with or without retinal hemorrhages. Twenty-one percent had neurological disease, several had changes in the CSF like GME, and 21% had AIHA. Half of the dogs had thrombocytopenia, and about one third had neutrophilia, monocytosis, eosinophilia, and anemia.

In cats, Bartonella henselae may cause fever, gingivitis and stomatitis, and lymphadenopathy. Diagnosis is based on serology and PCR.