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SUMMARY Recent observations have begun to support a role for Bartonella spp. as animal as well as human pathogens. Bartonella spp. are vector-transmitted, blood-borne, intracellular, gram-negative bacteria that can induce prolonged infection in the host. Persistent infections in domestic and wild animals result in a substantial reservoir of Bartonella organisms in nature that can serve as a source for inadvertent human infection. The prevalence of bacteremia can range from 50 to 95% in selected rodent, cat, deer, and cattle populations. Dogs infected with Bartonella spp. can develop lameness, endocarditis, granulomatous lymphadenitis, and peliosis hepatis, lesions that have also been reported in association with human infection. Understanding the role of Bartonella spp. as pathogens in cats and other wild or domestic animals awaits the results of additional studies. Considering the extensive animal reservoirs and the large number of insects that have been implicated in the transmission of Bartonella spp., both animal and human exposure to these organisms may be more substantial than is currently believed.

Human Bartonella infections result in diverse medical presentations, whereas many cats appear to tolerate chronic bacteremia without obvious clinical abnormalities. Eighteen specific-pathogen-free cats were inoculated with Bartonella henselae- and/orBartonella clarridgeiae-infected cat blood and monitored for 454 days. Relapsing bacteremia did not correlate with changes in protein profiles or differences in antigenic protein recognition. Intradermal skin testing did not induce a delayed type hypersensitivity reaction to cat scratch disease skin test antigen. Thirteen cats were euthanatized at the end of the study. Despite persistent infection, clinical signs were minimal and gross necropsy results were unremarkable. Histopathology revealed peripheral lymph node hyperplasia (in all of the 13 cats), splenic follicular hyperplasia (in 9 cats), lymphocytic cholangitis/pericholangitis (in 9 cats), lymphocytic hepatitis (in 6 cats), lymphoplasmacytic myocarditis (in 8 cats), and interstitial lymphocytic nephritis (in 4 cats). Structures suggestive of Bartonella were visualized in some Warthin-Starry stained sections, and Bartonella DNA was amplified from the lymph node (from 6 of the 13 cats), liver (from 11 cats) heart (from 8 cats), kidney (from 9 cats), lung (from 2 cats), and brain (from 9 cats). This study indicates that B. henselae or B. clarridgeiae can induce chronic infection following blood transfusion in specific-pathogen-free cats and thatBartonella DNA can be detected in blood, brain, lymph node, myocardium, liver, and kidney tissues of both blood culture-positive cats and blood culture-negative cats. Detection of histologic changes in these cats supports a potential etiologic role forBartonella species in several idiopathic disease processes in cats.

Five species of Bartonella have been reported to infect humans and cause a variety of diseases that can be difficult to diagnose. Four species of Bartonella have been reported to infect cats and dogs, and two of these species are considered to be zoonotic pathogens. Diagnosis of Bartonella infections is hampered by the slow, fastidious growth characteristics ofBartonella species. We report on the development of a single-step PCR-based assay for the detection and differentiation of medically relevant Bartonella species. PCR-mediated amplification of the 16S-23S rRNA intergenic region resulted in a product of a unique size for each Bartonella species, thereby allowing differentiation without the necessity of restriction fragment length polymorphism analysis or sequencing of the amplified product. The ability of the single-step PCR assay to differentiate between Bartonella species was determined with characterized isolates and blood samples from animals known to be infected with either Bartonella henselae, B. clarridgeiae, or B. vinsonii subsp.berkhoffii. The sensitivity of the single-step PCR assay relative to that of in vitro culture was determined with blood samples from B. henselae-infected cats. B. henselaetarget DNA was amplified from 100% of samples with greater than 50 CFU/ml and 80% of samples with 10 to 30 CFU/ml. The single-step assay described in the report expedites PCR-based detection and differentiation of medically relevant Bartonella species.

Vegetative valvular endocarditis involving the aortic and, to a lesser extent, mitral valves was diagnosed echocardiographically in a 3-year-old spayed female Labrador retriever. Historically, the dog had been treated with tetracycline hydrochloride and prednisolone for positive seroreactivity to Ehrlichia canis and antinuclear antigens. Although three aerobic and anaerobic blood cultures failed to grow bacteria, blood cultured simultaneously by the lysis centrifugation technique grew a fastidious, gram-negative organism. Despite an initial therapeutic response, the owner elected euthanasia 17 days later. Necropsy confirmed aortic and mitral valvular endocarditis. Bacteria phenotypically similar to Bartonella species were visualized in the heart valve by light and electron microscopy, and Bartonella DNA from a frozen heart valve was amplified by PCR. Subsequent phenotypic and genotypic characterization of the isolate, including biochemical testing, cellular fatty acid analysis, DNA hybridization, and sequencing of the 16S rRNA gene indicated that this organism, which can induce endocarditis in dogs, is a novel Bartonella subspecies containing an insertion sequence unique among currently recognized Bartonella species. The name Bartonella vinsonii subsp. berkoffii subsp. nov. will be proposed for this organism.

Shortly after adopting a 6-week-old cat, a veterinarian was bitten on the left index finger. Within 3 weeks, he developed headache, fever, and left axillary lymphadenopathy. Initial blood cultures from the cat and veterinarian were sterile. Repeat cultures from the cat grew Bartonella-like organisms with lophotrichous flagella. Sera from the veterinarian were not reactive against Bartonella henselae, B. quintana, or B. elizabethae antigens but were seroreactive (reciprocal titer, 1,024) against the feline isolate. Sequential serum samples from the cat were reactive against antigens of B. henselae (titer, 1,024), B. quintana (titer, 128), and the feline isolate (titer, 2,048). Phenotypic and genotypic characterization of this and six additional feline isolates, including microscopic evaluation, biochemical analysis, 16S rRNA gene sequencing, DNA-DNA hybridization, and PCR-restriction fragment length polymorphism of the 16S gene, 16S-23S intergenic spacer region, and citrate synthase gene identified the isolates as B. clarridgeiae. This is the first report of cat scratch disease associated with B. clarridgeiae.

Cardiac arrhythmias, endocarditis, or myocarditis was identified in 12 dogs, of which 11 were seroreactive to Bartonella vinsonii subspecies berkhoffii antigens. Historical abnormalities were highly variable but frequently included substantial weight loss, syncope, collapse, or sudden death. Fever was an infrequently detected abnormality. Cardiac disease was diagnosed following an illness of short duration in most dogs, but a protracted illness of at least 6 months' duration was reported for four dogs. Valvular endocarditis was diagnosed echocardiographically or histologically in eight dogs, two of which also had moderate to severe multifocal myocarditis. Four dogs lacking definitive evidence of endocarditis were included because of seroreactivity to B. vinsonii antigens and uncharacterized heart murmurs and/or arrhythmias. Alpha proteobacteria were not isolated from the blood by either conventional or lysis centrifugation blood culture techniques. Using PCR amplification and DNA sequencing of a portion of the 16S rRNA gene, B. vinsonii was identified in the blood or heart valves of three dogs. DNA sequence alignment of PCR amplicons derived from blood or tissue samples from seven dogs clustered among members of the alpha subdivision of the Proteobacteria and suggested the possibility of involvement of one or more alpha proteobacteria; however, because of the limited quantity of sequence, the genus could not be identified. Serologic or molecular evidence of coinfection with tick-transmitted pathogens, including Ehrlichia canis,Babesia canis, Babesia gibsonii, or spotted fever group rickettsiae, was obtained for seven dogs. We conclude thatB. vinsonii subsp. berkhoffii and closely related species of alpha proteobacteria are an important, previously unrecognized cause of arrhythmias, endocarditis, myocarditis, syncope, and sudden death in dogs.

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