Granulomatous Disease Associated withBartonellaInfection in 2 Dogs

Bartonella spp. seroepidemiology and associations with clinicopathologic findings in dogs in the United States

Background

Improved understanding of Bartonella spp. serology in dogs may aid clinical decision making.

Objective

Describe demographic and geographic patterns of Bartonella spp. seroreactivity in dogs, and describe hematologic and serum biochemical abnormalities in Bartonella spp. seroreactive and nonseroreactive dogs.

Animals

Serum samples from 5957 dogs in the United States, previously submitted to IDEXX Reference Laboratories.

Methods

Serum was tested using 3 indirect ELISAs for B. henselae, B. vinsonii subsp. berkhoffii, and B. koehlerae. Complete blood count and serum biochemistry panel results were reviewed retrospectively.

Results

Overall, 6.1% of dogs were Bartonella spp. seroreactive. Toy breeds were less likely to be seroreactive (3.9%) than mixed breeds (7.5%; adjusted odds ratio [aOR], 0.48; 95% confidence interval [CI], 0.32‐0.72), and dogs <1 year old were less likely to be seroreactive (3.4%) than dogs 1 to 5.5 years of age (7.3%; aOR, 0.42; 95% CI, 0.23‐0.72). Dogs in the West South Central (9.8%) and South Atlantic (8.8%) regions were more likely than dogs elsewhere in the United States to be seroreactive (aOR, 2.22; 95% CI, 1.31‐3.87; aOR, 2.44; 95% CI, 1.38‐4.36).

Conclusions and Clinical Importance

Demographic and geographic findings for Bartonella spp. exposure were broadly comparable to previously reported patterns.

Ecological and Socioeconomic Factors Associated with Bartonella henselae Exposure in Dogs Tested for Vector-Borne Diseases in North Carolina

Bartonella henselae is a zoonotic vector-borne pathogen affecting both humans and dogs. Little is known about the epidemiology of B. henselae in dogs, including risk factors associated with exposure. The objectives of this study were to map the current distribution of B. henselae in dogs in North Carolina (NC) and to identify ecological and socioeconomic factors influencing B. henselae seroreactivity. Results from 4446 B. henselae serology samples from dogs in NC submitted by veterinarians for clinical diagnostic testing to the North Carolina State University College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2004 and December 31, 2015 were retrospectively reviewed. These results were used to generate a map of B. henselae seroreactivity. To account for sparsely sampled areas, statistical smoothing using head banging and areal interpolation kriging was performed. Using previously described risk factors for exposure to canine tick-borne diseases, eight multivariable logistic regression models based on biologically plausible hypotheses were tested, and a final model was selected using an Akaike's Information Criterion weighted-average approach. Seroreactivity among dogs tested for vector-borne disease was variable across the state: higher along the southern/eastern coastal plains and eastern Piedmont, and lower in the western mountains. Of 25 explanatory factors considered, the model combining demographic, socioeconomic, climatic, and land use variables fits best. Based on this model, female intact sex and increasing percentage of the county with low-intensity development and evergreen forest were associated with higher seroreactivity. Conversely, moderate development, increasing median household income, and higher temperature range and relative humidity were associated with lower seroreactivity. This model could be improved, however, by including local and host-scale factors that may play a significant role in dogs' exposure.

Characterisation and outcome of idiopathic pyogranulomatous lymphadenitis in 64 English springer spaniel dogs

OBJECTIVES

To describe the history, clinicopathological abnormalities, diagnostic imaging findings, lymph node cytological/histological appearance, treatment and outcome of English springer spaniels diagnosed with idiopathic pyogranulomatous lymphadenitis.

MATERIALS AND METHODS

In this retrospective UK-based multicentre study, 64 dogs were recruited from 10 referral centres, 32 first-opinion practices and three histopathology/cytology laboratories, between 2010 and 2016.

RESULTS

The median age at presentation was 6 years (range: 0.17 to 11.75). Neutered females were frequently affected. Pyrexia (83.8%), peripheral lymphadenomegaly (78.4%), dermatological lesions (72.9%), lethargy (67.6%), hyporexia (54%), diarrhoea (29.7%), coughing (24.3%), epistaxis, sneezing or nasal discharge (21.6%), ocular signs (21.6%) and vomiting (16.2%) were reported in dogs for which the history and physical examination records were available. Popliteal (45.3%), superficial cervical (35.9%) and submandibular (37.5%) lymphadenomegaly were frequently reported. Haematology and serum biochemistry revealed non-specific changes. When undertaken, testing for infectious diseases was negative in all cases. Lymph node cytology, histopathology or both demonstrated mixed inflammatory (27%), pyogranulomatous (24%), neutrophilic (20%) or granulomatous (11%) lymphadenitis. Treatment details were available for 38 dogs, with 34 receiving prednisolone for a median duration of 15 weeks (range: 1 to 28 weeks). A good to excellent clinical response was reported in all but one case. Ten dogs relapsed after discontinuing prednisolone.

CLINICAL SIGNIFICANCE

Idiopathic pyogranulomatous lymphadenitis should be considered as a differential diagnosis for lymphadenopathy and pyrexia in English springer spaniels. The characteristics of the disease, absence of identifiable infectious aetiology and response to glucocorticoid therapy suggest an immune-mediated aetiology.

Bartonella infections in cats and dogs including zoonotic aspects

Bartonellosis is a vector-borne zoonotic disease with worldwide distribution that can infect humans and a large number of mammals including small companion animals (cats and dogs). In recent years, an increasing number of studies from around the world have reported Bartonella infections, although publications have predominantly focused on the North American perspective. Currently, clinico-pathological data from Europe are more limited, suggesting that bartonellosis may be an infrequent or underdiagnosed infectious disease in cats and dogs. Research is needed to confirm or exclude Bartonella infection as a cause of a spectrum of feline and canine diseases. Bartonella spp. can cause acute or chronic infections in cats, dogs and humans. On a comparative medical basis, different clinical manifestations, such as periods of intermittent fever, granulomatous inflammation involving the heart, liver, lymph nodes and other tissues, endocarditis, bacillary angiomatosis, peliosis hepatis, uveitis and vasoproliferative tumors have been reported in cats, dogs and humans. The purpose of this review is to provide an update and European perspective on Bartonella infections in cats and dogs, including clinical, diagnostic, epidemiological, pathological, treatment and zoonotic aspects.

Bartonella Seroepidemiology in Dogs from North America, 2008-2014

BACKGROUND

Improved understanding of Bartonella species seroepidemiology in dogs may aid clinical decision making and enhance current understanding of naturally occurring arthropod vector transmission of this pathogen.

OBJECTIVES

To identify demographic groups in which Bartonella exposure may be more likely, describe spatiotemporal variations in Bartonella seroreactivity, and examine co-exposures to other canine vector-borne diseases (CVBD).

ANIMALS

A total of 15,451 serology specimens from dogs in North America were submitted to the North Carolina State University, College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2008, and December 31, 2014.

METHODS

Bartonella henselae, Bartonella koehlerae, and Bartonella vinsonii subspecies berkhoffii indirect fluorescent antibody (IFA) serology results, as well as results from a commercial assay kit screening for Dirofilaria immitis antigen and Ehrlichia species, Anaplasma phagocytophilum, and Borrelia burgdorferi antibodies, and Ehrlichia canis, Babesia canis, Babesia gibsoni, and Rickettsia species IFA results were reviewed retrospectively.

RESULTS

Overall, 3.26% of dogs were Bartonella spp. seroreactive; B. henselae (2.13%) and B. koehlerae (2.39%) were detected more frequently than B. vinsonii subsp. berkhoffii (1.42%, P < 0.0001). Intact males had higher seroreactivity (5.04%) than neutered males (2.87%, P < 0.0001) or intact or spayed females (3.22%, P = 0.0003). Mixed breed dogs had higher seroreactivity (4.45%) than purebred dogs (3.02%, P = 0.0002). There was no trend in seasonal seroreactivity; geographic patterns supported broad distribution of exposure, and co-exposure with other CVBD was common.

CONCLUSIONS AND CLINICAL IMPORTANCE

Bartonella spp. exposure was documented throughout North America and at any time of year. Male intact dogs, mixed breed dogs, and dogs exposed to other CVBD have higher seroreactivity to multiple Bartonella species.

Bacterial microbiome of the nose of healthy dogs and dogs with nasal disease

The role of bacterial communities in canine nasal disease has not been studied so far using next generation sequencing methods. Sequencing of bacterial 16S rRNA genes has revealed that the canine upper respiratory tract harbors a diverse microbial community; however, changes in the composition of nasal bacterial communities in dogs with nasal disease have not been described so far. Aim of the study was to characterize the nasal microbiome of healthy dogs and compare it to that of dogs with histologically confirmed nasal neoplasia and chronic rhinitis. Nasal swabs were collected from healthy dogs (n = 23), dogs with malignant nasal neoplasia (n = 16), and dogs with chronic rhinitis (n = 8). Bacterial DNA was extracted and sequencing of the bacterial 16S rRNA gene was performed. Data were analyzed using Quantitative Insights Into Microbial Ecology (QIIME). A total of 376 Operational Taxonomic Units out of 26 bacterial phyla were detected. In healthy dogs, Moraxella spp. was the most common species, followed by Phyllobacterium spp., Cardiobacteriaceae, and Staphylococcus spp. While Moraxella spp. were significantly decreased in diseased compared to healthy dogs (p = 0.005), Pasteurellaceae were significantly increased (p = 0.001). Analysis of similarities used on the unweighted UniFrac distance metric (p = 0.027) was significantly different when nasal microbial communities of healthy dogs were compared to those of dogs with nasal disease. The study showed that the canine nasal cavity is inhabited by a highly species-rich bacterial community, and suggests significant differences between the nasal microbiome of healthy dogs and dogs with nasal disease.

Retrospective characterisation and outcome of canine idiopathic mesenteric purulent lymphadenitis and lymph node abscesses at a teaching hospital from 2005 to 2015

BACKGROUND

Idiopathic purulent mesenteric lymphadenitis or lymph node abscessation, even though rare in dogs, are important diseases in which rapid diagnosis and treatment is critical. This study aimed to characterise the typical features of these conditions in dogs.

MATERIAL AND METHODS

Archived records from 2005 to 2015 were retrospectively evaluated for the occurrence of idiopathic purulent mesenteric lymphadenitis or lymph node abscesses in dogs. History, physical and clinicopathological abnormalities, diagnostic tests performed, treatment and outcome were reviewed.

RESULTS

A total of 14 cases with histopathologic and/or cytologic confirmation were identified. Typically, there were gastrointestinal signs including abdominal pain and elevated body temperature. Blood analysis revealed non-specific inflammatory changes including elevated C-reactive protein. Half of the bacterial cultures from lymph nodes showed growth of various bacteria. A primary cause was not identified in any case. Out of 14 cases, 10 cases underwent surgery and all dogs were discharged from the hospital. Three suffered from a relapse between 1 and 5 months after discharge but were successfully managed with antibiotics.

CONCLUSION AND CLINICAL RELEVANCE

Idiopathic purulent mesenteric lymphadenitis or lymph node abscessation are infrequent but clinically important diseases. Surgical, symptomatic and antibiotic treatment led to resolution of clinical signs in the evaluated cases. Thorough and standardised diagnostic workup and treatment of future cases are necessary to investigate possible pathogeneses and optimal therapeutic options. Outcome was favourable overall.

Bartonella spp. - a chance to establish One Health concepts in veterinary and human medicine

Infectious diseases remain a remarkable health threat for humans and animals. In the past, the epidemiology, etiology and pathology of infectious agents affecting humans and animals have mostly been investigated in separate studies. However, it is evident, that combined approaches are needed to understand geographical distribution, transmission and infection biology of “zoonotic agents”. The genus Bartonella represents a congenial example of the synergistic benefits that can arise from such combined approaches: Bartonella spp. infect a broad variety of animals, are linked with a constantly increasing number of human diseases and are transmitted via arthropod vectors. As a result, the genus Bartonella is predestined to play a pivotal role in establishing a One Health concept combining veterinary and human medicine.

Resolution of spontaneous hemoabdomen secondary to peliosis hepatis following surgery and azithromycin treatment in a Bartonella species infected dog

OBJECTIVE

To describe a case of hemoperitonium in a dog with Bartonellosis and peliosis hepatis (PH) lesions that resolved following antimicrobial therapy.

CASE SUMMARY

A 3-year-11-month-old 22.5 kg female spayed mixed breed dog presented for progressive lethargy and vomiting. An abdominal ultrasonographic examination revealed moderate ascites, which when sampled was nonclotting hemorrhagic fluid. An exploratory laparotomy revealed a large volume of nonclotted blood in the dog's abdomen and blood-filled vesicular lesions dispersed diffusely along multiple lobes of the liver. Biopsies revealed lesions indicative of PH. Serology testing for Bartonella species was positive. Treatment with azithromycin resulted in Bartonella serology negative status and no further evidence of hemoperitonium at recheck examination 12 months after initial presentation.

NEW OR UNIQUE INFORMATION PROVIDED

This is the first reported case of PH and hemoperitoneum in a Bartonella species serology positive dog wherein treatment with azithromycin resulted in serology negative status. There have been no subsequent episodes of hemoperitoneum in the 12 months since treatment.

Ecological diversity of Bartonella species infection among dogs and their owner in Virginia

Bartonella species comprise a genus of gram-negative, fastidious, intracellular bacteria that have been implicated in association with an increasing spectrum of disease manifestations in dogs and human patients. In this study, chronic canine and human disease, for which causation was not diagnostically defined, were reported by the breeder of a kennel of Doberman pinschers. In addition to other diagnostic tests, serology, polymerase chain reaction, and enrichment blood culture were used to assess the prevalence of Bartonella sp. infection in the dogs and their owner. From five dogs, Bartonella vinsonii subsp. berkhoffii genotype I, multiple Bartonella henselae strains, and a species most similar to Candidatus B. volans, a rodent-associated Bartonella sp., were amplified and sequenced from biopsy tissues, cerebrospinal fluid, or blood enrichment cultures. The owner was bacteremic with B. vinsonii subsp. berkhoffii genotype I, the same subsp. and genotype detected in one of her dogs. These results further emphasize the ecological complexity of Bartonella sp. transmission in nature.

Bartonella infection: treatment and drug resistance

Bartonella species, which belong to the α-2 subgroup of Proteobacteria, are fastidious Gram-negative bacteria that are highly adapted to their mammalian host reservoirs. Bartonella species are responsible for different clinical conditions affecting humans, including Carrion's disease, cat scratch disease, trench fever, bacillary angiomatosis, endocarditis and peliosis hepatis. While some of these diseases can resolve spontaneously without treatment, in other cases, the disease is fatal without antibiotic treatment. In this article, we discuss the antibiotic susceptibility patterns of Bartonella species, detected using several methods. We also provide an overview of Bartonella infection in humans and animals and discuss the antibiotic treatment recommendations for the different infections, treatment failure and the molecular mechanism of antibiotic resistance in these bacteria.

Detection and genetic diversity of Bartonella vinsonii subsp. berkhoffii strains isolated from dogs in Ankara, Turkey

Bartonella vinsonii subsp. berkhoffii has been identified as an important pathogen in dogs and is an emerging pathogen in people with zoonotic potential. This study aimed to isolate Bartonella spp. in 250 blood samples collected from dogs in the province of Ankara, Turkey, between October 2006 and March 2007. The typing of the 23 isolates was carried out by PCR for citrate synthase (gltA) and the 16S-23S intergenic transcribed spacer (ITS). The prevalence of bacteremia was 9.2% in 250 samples. Among 170 shelter dogs, 21 (12.4%) were bacteremic for B. vinsonii subsp. berkhoffii, while the B. vinsonii subsp. berkhoffii bacteremia rate was 5% (2/40) for the stray dogs. B. vinsonii subsp. berkhoffii was not isolated from the pet dogs. The prevalence of bacteremia was found to be 25.5% (13/51) in shelter dogs aged less than one year old. All of the isolates were identified as B.vinsonii subsp. berkhoffii genotype III. In some isolates, MseI digest for gltA was found to be different from the American and European strains due to a single nucleotide change.

Infective endocarditis in a dog and the phylogenetic relationship of the associated "Bartonella rochalimae" strain with isolates from dogs, gray foxes, and a human

The first case of canine endocarditis caused by "Bartonella rochalimae" is reported. By PCR-restriction fragment length polymorphism, sequence, and phylogenetic analyses, Bartonella isolates from a dog with endocarditis, 22 gray foxes, and three dogs, described as B. clarridgeiae like, were confirmed to belong to the new species "B. rochalimae," suggesting canids as the natural reservoir.

Microbial culture of blood samples and serologic testing for bartonellosis in cats with chronic rhinosinusitis

OBJECTIVE

To assess the role of Bartonella spp in chronic rhinosinusitis (CRS) by determining detection rates for the organism by serologic testing and microbial culture of blood samples for Bartonella spp in cats with CRS and control cats (cats with other nasal diseases, cats with systemic illnesses, and healthy cats).

DESIGN

Prospective case-control study.

ANIMALS

19 cats with CRS, 10 cats with other nasal diseases, 15 cats with systemic illness, and 15 healthy cats. Procedures-Serologic testing for Bartonella clarridgeiae and Bartonella henselae and microbial culture of blood samples were conducted in all cats. In cats with CRS and cats with other nasal diseases, a nasal biopsy specimen was submitted, when available, for tissue PCR assay to detect Bartonella spp.

RESULTS

9 of 19 cats with CRS had positive results for serologic testing for 1 or both Bartonella spp; whereas, 4 of 10 cats with other nasal diseases, 2 of 15 cats with systemic diseases, and 4 of 15 healthy cats had positive results for serologic testing to detect Bartonella spp. These values did not differ significantly among groups. Microbial culture of blood samples yielded B henselae in 1 cat with a nasopharyngeal abscess. The PCR assay for Bartonella spp in nasal tissues yielded negative results for 9 of 9 cats with CRS and 5 of 5 cats with other nasal diseases.

CONCLUSIONS AND CLINICAL RELEVANCE

A role for Bartonella spp in the pathogenesis of CRS in cats was not supported by results of this study.

Detection ofBartonella henselaeDNA in two dogs with pyogranulomatous lymphadenitis

CASE DESCRIPTION

1 dog evaluated because of inappetence and lameness of the left hind limb of 1 day's duration and 1 dog evaluated because of inappetence, fever, and lymphadenopathy of 2 weeks' duration.

CLINICAL FINDINGS

Histologic examination of excisional biopsy specimens from lymph nodes revealed pyogranulomatous lymphadenitis in both dogs. Quantitative real-time PCR assays detected Bartonella henselae DNA in blood samples and affected lymph node specimens from both dogs. Antibodies against B. henselae were not detected via immunofluorescent antibody testing during active disease in either dog.

TREATMENT AND OUTCOME

1 dog recovered after 6 weeks of treatment with doxycycline (5 mg/kg [2.3 mg/lb], p.o., q 12 h), whereas the other dog recovered after receiving a combination of azithromycin (14.5 mg/kg [6.6 mg/lb], p.o., q 24 h for 21 days), doxycycline (17.3 mg/kg [7.9 mg/lb], p.o., q 24 h for 4 weeks), and immunosuppressive corticosteroid (prednisone [3 mg/kg {1.4 mg/lb}, p.o., q 24 h], tapered by decreasing the daily dose by 25% every 2 weeks) treatment.

CLINICAL RELEVANCE

B. henselae is implicated as a possible cause or a cofactor in the development of pyogranulomatous lymphadenitis in dogs. In dogs with pyogranulomatous lymphadenitis, immunofluorescent assays may not detect antibodies against B. henselae. Molecular testing, including PCR assay of affected tissues, may provide an alternative diagnostic method for detection of B. henselae DNA in pyogranulomatous lymph nodes.

Bartonella species as a potential cause of epistaxis in dogs

Infection with a Bartonella species was implicated in three cases of epistaxis in dogs, based upon isolation, serology, or PCR amplification. These cases, in conjunction with previously published reports, support a potential role for Bartonella spp. as a cause of epistaxis in dogs and potentially in other animals, including humans.

Clinicopathological Abnormalities and Treatment Response in 24 Dogs Seroreactive to Bartonella vinsonii (berkhoffii) Antigens

Bartonella vinsonii (B. vinsonii) subspecies berkhoffii is a recently recognized cause of endocarditis, myocarditis, and granulomatous disease in dogs. In an effort to elucidate other potential disease manifestations, the case records of 24 dogs that were seroreactive to B. vinsonii (berkhoffii) antigens were studied retrospectively. Diagnoses included immune-mediated hemolytic anemia, neutrophilic or granulomatous meningoencephalitis, neutrophilic polyarthritis, cutaneous vasculitis, and uveitis. Repeated B. vinsonii (berkhoffii) antibody titers became negative after treatment. This study indicates that a diverse spectrum of disease manifestations and clinicopathological abnormalities can be detected in dogs that are seroreactive to B. vinsonii (berkhoffii) antigens.

Isolation of Bartonella washoensis from a dog with mitral valve endocarditis

We report the first documented case of Bartonella washoensis bacteremia in a dog with mitral valve endocarditis. B. washoensis was isolated in 1995 from a human patient with cardiac disease. The main reservoir species appears to be ground squirrels (Spermophilus beecheyi) in the western United States. Based on echocardiographic findings, a diagnosis of infective vegetative valvular mitral endocarditis was made in a spayed 12-year-old female Doberman pinscher. A year prior to presentation, the referring veterinarian had detected a heart murmur, which led to progressive dyspnea and a diagnosis of congestive heart failure the week before examination. One month after initial presentation, symptoms worsened. An emergency therapy for congestive heart failure was unsuccessfully implemented, and necropsy evaluation of the dog was not permitted. Indirect immunofluorescence tests showed that the dog was strongly seropositive (titer of 1:4,096) for several Bartonella antigens (B. vinsonii subsp. berkhoffii, B. clarridgeiae, and B. henselae), highly suggestive of Bartonella endocarditis. Standard aerobic and aerobic-anaerobic cultures were negative. However, a specific blood culture for Bartonella isolation grew a fastidious, gram-negative organism 7 days after being plated. Phenotypic and genotypic characterizations of the isolate, including partial sequencing of the citrate synthase (gltA), groEL, and 16S rRNA genes, indicated that this organism was identical to B. washoensis. The dog was seronegative for all tick-borne pathogens tested (Anaplasma phagocytophilum, Ehrlichia canis, and Rickettsia rickettsii), but the sample was highly positive for B. washoensis (titer of 1:8,192) and, according to indirect immunofluorescent-antibody assay, weakly positive for phase II Coxiella burnetii infection.

Bartonella vinsonii subspecies berkhoffi as a possible cause of anterior uveitis and choroiditis in a dog

A 2-year old, neutered, female spaniel mixed breed was referred to the North Carolina State University Veterinary Teaching Hospital for evaluation of bilateral anterior uveitis. The dog was febrile and, in addition to anterior uveitis, multifocal hyporeflective lesions were present in the tapetal fundus of both eyes. The antibody titer for Bartonella vinsonii subspecies berkhoffi was positive (1 : 512). Aqueous paracentesis was performed for PCR in an attempt to detect B. vinsonii in the eye but was unsuccessful. The ocular manifestations of Bartonella infection in humans are currently expanding as more sensitive serologic and PCR techniques are being developed to identify Bartonella spp. In addition to optic neuritis and neuroretinitis, retinochoroidal lesions are one of the most common manifestations of B. henselae infection, and are frequently accompanied by vitreous or anterior segment inflammation. Diagnosis of a Bartonella infection in humans can be made on serology alone, in conjunction with ocular examination findings. The ultimate proof of B. vinsonii (berkhoffi) as a direct cause of ocular disease would be detection of the infectious agent in the eye. However, it is unknown at this time whether Bartonella causes ocular disease primarily, secondarily via an autoimmune reaction, or both. Due to the difficulties associated with culture of Bartonella spp. and the limitations of PCR, serology is currently the most useful tool for screening dogs for possible Bartonella spp. infection. In the case presented here, even though the PCR was negative, the clinical signs of anterior uveitis and choroiditis might reasonably be associated with B. vinsonii (berkhoffi) seroreactivity, which was repeatable on three separate occasions. Clinical improvement was also accompanied by a post-treatment decrease in B. vinsonii (berkhoffi) seroreactivity, potentially supporting resolution of Bartonella infection in this dog. This is the first reported case of a possible association between uveitis, choroiditis and Bartonella infection in the dog, without clinical manifestations of other organ or tissue involvement. Future studies based on PCR analysis of intraocular fluids may clarify the involvement of B. vinsonii (berkhoffi) in dogs with intraocular inflammatory disease. Furthermore, performing fluorescein angiography in dogs with elevated Bartonella titers may also prove useful in the identification and characterization of lesions.

The immunologic response of dogs to Bartonella vinsonii subspecies berkhoffii antigens: as assessed by Western immunoblot analysis

Bartonella vinsonii subspecies berkhoffii is a recently recognized zoonotic pathogen that causes endocarditis, granulomatous rhinitis, and granulomatous lymphadenitis in dogs. Isolation of B. vinsonii (berkhoffii) from blood or tissue samples is frequently unsuccessful; therefore, diagnosis is primarily dependent on serologic or molecular testing modalities. Because previous canine serologic studies have used an indirect immunofluorescence assay (IFA), without Western immunoblot (WI) confirmation, the overall objective of this study was to examine the diagnostic use of WI for confirmation of B. vinsonii (berkhoffii) infection in dogs. To confirm that agar-grown and cell culture-grown organisms yielded similar patterns of WI antigenic protein recognition, the 2 preparations were compared using IFA-reactive sera obtained from dogs experimentally infected with B. vinsonii (berkhoffii). Temporal changes in the pattern of antigenic protein recognition were characterized using sera obtained from dogs at various time points after experimental B. vinsonii (berkhoffii) infection. The specificity of B. vinsonii (berkhoffii) WI was examined by testing canine sera that were reactive to B. henselae, B. clarridgeiae, Ehrlichia canis, Rickettsia rickettsii, Babesia canis, Anaplasma phagocytophilum (previously E. equi), or Brucella canis antigens. Clinical accessions including serum samples obtained from B. vinsonii (berkhoffii) culture-positive dogs and B. vinsonii (berkhoffii) culture-negative dogs that were IFA seroreactive to B. vinsonii (berkhoffii) antigens were examined by WI. The results of this study indicate that WI using agar-grown or cell culture-grown B. vinsonii (berkhoffii) antigens produce identical patterns of antigenic protein recognition. After experimental infection, there is a progressive increase in the number of antigenic proteins that are recognized by WI, with the 33-kD antigen representing the first and the most persistent antigen recognized by B. vinsonii (berkhoffii)-infected dogs. Regarding specificity, sera from dogs that were reactive to various heterologous antigens did not recognize B. vinsonii (berkhoffii) antigens by IFA or WI, and sera from dogs experimentally infected with B. henselae did not recognize B. vinsonii (berkhoffii) antigens by WI. Regarding clinical accessions, there was good agreement between B. vinsonii (berkhoffii) IFA test results and WI analysis. Western immunoblot analysis can be used to detect or confirm exposure to B. vinsonii (berkhoffii) in dogs.

Clinical impact of persistent Bartonella bacteremia in humans and animals

Bartonella spp. are emerging vector-borne pathogens that cause persistent, often asymptomatic bacteremia in their natural hosts. As our knowledge progresses, it appears that chronic infection may actually predispose the host to mild, insidious nonspecific manifestations or induce, in selected instances, severe diseases. Persistent asymptomatic bacteremia is most common in animals that serve as the main reservoir for the specific Bartonella. In humans, these organisms are B. bacilliformis and B. quintana. Other Bartonella species, for which humans are not the natural reservoir, tend to cause persistent bacteremia only in immunodeficient individuals. In some of these individuals, endothelial cell proliferation may create lesions such as bacillary angiomatosis or bacillary peliosis. In cats, bacteremia of variable level and continuity may last for years. Some strains of B. henselae may induce clinical manifestations, including fever, mild neurological signs, reproductive disorders, whereas others do not induce clinically obvious disease. Reproductive disorders have also been reported in mice experimentally infected with B. birtlesii. Finally, canids constitute the most interesting naturally occurring animal model for the human disease. Like immunocompetent people, healthy dogs only occasionally demonstrate long-term bacteremia when infected with Bartonella spp. However, some dogs develop severe clinical manifestations, such as endocarditis, and the pathologic spectrum associated with Bartonella spp. infection in domestic dogs is rapidly expanding and resembles the infrequently reported clinical entities observed in humans. In coyotes, persistent bacteremia is more common than in domestic dogs. It will be of interest to determine if coyotes develop clinical or pathological indications of infection.

Bartonella henselae and Bartonella elizabethae as potential canine pathogens

Bartonella henselae or Bartonella elizabethae DNA from EDTA-anticoagulated blood samples obtained from four dogs was amplified and sequenced. The results showed that B. elizabethae should be added to the list of Bartonella species (i.e., B. vinsonii subsp. berkhoffii, B. henselae, and B. clarridgeiae) that are currently recognized as infectious agents in dogs. Furthermore, these results may have potential zoonotic implications, particularly if dogs can serve as a previously unrecognized reservoir for B. henselae. Although the clinical relevance of these observations remains to be determined, it is possible that molecular diagnostic techniques such as PCR may help to implicate a spectrum of Bartonella spp. as a cause of or a cofactor in chronic canine and human diseases of poorly defined causation.

Aortic valve endocarditis in a dog due to Bartonella clarridgeiae

We report the first documented case of endocarditis associated with Bartonella clarridgeiae in any species. B. clarridgeiae was identified as a possible etiological agent of human cat scratch disease. Infective vegetative valvular aortic endocarditis was diagnosed in a 2.5-year-old male neutered boxer. Historically, the dog had been diagnosed with a systolic murmur at 16 months of age and underwent balloon valvuloplasty for severe valvular aortic stenosis. Six months later, the dog was brought to a veterinary hospital with an acute third-degree atrioventricular block and was diagnosed with infective endocarditis. The dog died of cardiopulmonary arrest prior to pacemaker implantation. Necropsy confirmed severe aortic vegetative endocarditis. Blood culture grew a fastidious, gram-negative organism 8 days after being plated. Phenotypic and genotypic characterization of the isolate, including partial sequencing of the citrate synthase (gltA) and 16S rRNA genes indicated that this organism was B. clarridgeiae. DNA extraction from the deformed aortic valve and the healthy pulmonic valve revealed the presence of B. clarridgeiae DNA only from the diseased valve. No Borrelia burgdorferi or Ehrlichia sp. DNA could be identified. Using indirect immunofluorescence tests, the dog was seropositive for B. clarridgeiae and had antibodies against Ehrlichia phagocytophila but not against Ehrlichia canis, Ehrlichia ewingii, B. burgdorferi, or Coxiella burnetii.

Infection with Bartonella weissii and detection of Nanobacterium antigens in a North Carolina beef herd

Very recently, Bartonella organisms have been isolated from large ruminants (deer, elk, and dairy and beef cattle) located in the United States and in France. In this study, we report the serologic, microbiologic, and molecular findings related to the isolation of a Bartonella species in North Carolina beef cattle and the detection of nanobacterial antigen using a commercially available enzyme-linked immunosorbent assay. Between August 1998 and September 1999, blood was collected from 38 cattle ranging in age from 1 month to 6.5 years. After a 1-month incubation period, a Bartonella sp. was isolated on a 5% rabbit blood agar plate from three of six EDTA blood samples. PCR amplification of the 16S rRNA gene from all three isolates resulted in a DNA sequence that was 100% identical to that of B. weissii 16S rRNA (GenBank no. AF199502). By IFA testing, 36 of 38 cattle had antibodies (> or =1:64) to Bartonella weissii (bovine origin) antigens. Nanobacterial antigen was detected in 22 of 22 serum samples. We conclude that infection with an organism similar or closely related to B. weissii can occur in North Carolina cattle and that although their actual existence is still controversial Nanobacterium antigens were detected with a commercially available test kit. The epidemiology, vector biology, and potential pathogenicity of these organisms in cattle deserve future consideration.

Bartonella infection in animals: carriership, reservoir potential, pathogenicity, and zoonotic potential for human infection

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.

Peliosis hepatis in a dog infected with Bartonella henselae

A 6-year-old spayed female Golden Retriever was examined because of generalized weakness and abdominal distention. Abdominal ultrasonography revealed a large quantity of peritoneal fluid. In addition, the liver appeared larger than normal and contained multiple, small, nodular masses and cyst-like structures. Abdominal exploratory surgery was performed, and 5 L of serosanguineous peritoneal fluid was removed. Gross lesions were not found in the stomach, kidneys, intestines, adrenal glands, or urinary bladder. There were diffuse cystic nodules in all liver lobes. The dog did not recover from anesthesia. A diagnosis of peliosis hepatis was made on the basis of gross and histologic appearance of the liver. A polymerase chain reaction assay revealed Bartonella henselae DNA in liver specimens. To our knowledge, this is the first report of molecular evidence of B henselae infection in a dog with peliosis hepatis.