Comparison of Serological and Molecular Assays for Bartonella Species in Dogs with Hemangiosarcoma

The role of vector-borne pathogens and cardiac Striatin genotype on survival in boxer dogs with arrhythmogenic right ventricular cardiomyopathy

INTRODUCTION/OBJECTIVES

Risk factors for severe disease in boxer dogs with arrhythmogenic right ventricular cardiomyopathy (ARVC) are not well understood. This study's objective was to determine whether Striatin genotype or canine vector-borne pathogen (CVBP) exposure/infection in boxer dogs with ARVC was associated with disease severity or survival.

ANIMALS

Sixty-four client-owned, adult boxer dogs with ARVC were included in the study.

MATERIALS AND METHODS

This was a prospective descriptive study. Disease severity was determined by echocardiography and Holter monitoring. Potential risk factors included CVBP exposure/infection (Anaplasma spp., Babesia spp., Bartonella spp., Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia spp., and Rickettsia spp.) and Striatin genotype.

RESULTS

The median survival time after enrollment was 270 days (95% confidence interval [CI]: 226-798 days), and the median age at the time of death or censoring was 11 years (95% CI: 10.3-11.7 years). Striatin mutation genotype results included 31 homozygous-negative, 26 heterozygous-positive, and seven homozygous-positive boxer dogs. Ten boxer dogs had exposure to Bartonella spp., four to Rickettsia, two to Ehrlichia spp., and one to Anaplasma spp. Striatin homozygous-positive boxer dogs had a shorter median survival time (93 days vs. 373 days for heterozygous [P=0.010] and 214 days for homozygous negative [P=0.036]). Exposure/infection to CVBP was not associated with median survival time or age at the time of death.

DISCUSSION

Striatin homozygous positive boxer dogs with ARVC had shorter survival times and were younger at the time of death. Exposure or infection with CVBP did not appear to influence survival time.

STUDY LIMITATIONS

Selection bias for more severe disease limited the ability to assess the relationship between CVBP infection/exposure and disease severity, and overall small sample size limited statistical power. Extracardiac disease and treatment protocols were not controlled.

CONCLUSIONS

Striatin genotype screening can be considered for prognostic information. Exposure/infection to CVBP appears unlikely to influence survival time for boxer dogs with ARVC.

Antibodies to Borrelia burgdorferi and Bartonella species in serum and synovial fluid from people with rheumatic diseases

Vector-borne infections may underlie some rheumatic diseases, particularly in people with joint effusions. This study aimed to compare serum and synovial fluid antibodies to B. burgdorferi and Bartonella spp. in patients with rheumatic diseases. This observational, cross-sectional study examined paired synovial fluid and serum specimens collected from 110 patients with joint effusion between October 2017 and January 2022. Testing for antibodies to B. burgdorferi (using CDC criteria) and Bartonella spp. via two indirect fluorescent antibody (IFA) assays was performed as part of routine patient care at the Institute for Specialized Medicine (San Diego, CA, USA). There were 30 participants (27%) with positive two-tier B. burgdorferi serology and 26 participants (24%) with IFA seroreactivity (≥1:256) to B. henselae and/or B. quintana. Both B. burgdorferi IgM and IgG were detected more frequently in synovial fluid than serum: 27% of patients were either IgM or IgG positive in synovial fluid, compared to 15.5% in serum (P = 0.048). Conversely, B. henselae and B. quintana antibodies were detected more frequently in serum than synovial fluid; overall only 2% of patients had positive IFA titers in synovial fluid, compared to 24% who had positive IFA titers in serum (P < 0.001). There were no significant associations between B. burgdorferi or Bartonella spp. seroreactivity with any of the clinical rheumatological diagnoses. This study provides preliminary support for the importance of synovial fluid antibody testing for documenting exposure to B. burgdorferi but not for documenting exposure to Bartonella spp.

IMPORTANCE

This study focuses on diagnostic testing for two common vector-borne diseases in an affected patient population. In it, we provide data showing that antibodies to B. burgdorferi, but not Bartonella spp., are more commonly found in synovial fluid than serum of patients with joint effusion. Since Lyme arthritis is a common-and sometimes difficult to diagnose-rheumatic disease, improving diagnostic capabilities is of utmost importance. While our findings are certainly not definitive for changes to practice, they do suggest that synovial fluid could be a useful sample for the clinical diagnosis of Lyme disease, and future prospective studies evaluating this claim are warranted.

Progressive angiomatosis, resembling human skeletal-extraskeletal angiomatosis, arising in multiple digits in two dogs

Two dogs presented with progressive, expansile and invasive lesions on a hind paw. Case 1, a 10-year-old female Shetland sheepdog had diffusive and aggressive-looking lesions on the middle digits of the left hind paw. Radiographic examination showed invasion into and destruction of the underlying bone. A malignant tumour was suspected initially; however, histological features of atypical vascular proliferations without mitotic activity were consistent with progressive angiomatosis. Case 2, an 11-year-old female English springer spaniel presented with similar lesions in the same toes, also involving bone. Progressive angiomatosis was suspected clinically, as tumour cells were not detected by cytology and screening did not detect metastatic disease. Histopathology confirmed the diagnosis. Progressive angiomatosis is an uncommon non-malignant condition which should be considered as a differential diagnosis for radiographically lytic digital lesions.

Blood Supplementation Enhances Bartonella henselae Growth and Molecular Detection of Bacterial DNA in Liquid Culture

Bacteria of the genus Bartonella, a member of the Alphaproteobacteria, are fastidious, Gram-negative, aerobic bacilli that comprise numerous species, subspecies, and genotypes. Bartonella henselae, with a worldwide distribution, infects cats, dogs, horses, humans, and other mammals. Diagnostically, direct detection of Bartonella henselae in patient blood specimens by culture or molecular methods is required to confirm infection with this bacterium. Enrichment blood culture combined with quantitative PCR (qPCR) or ddPCR enhances the sensitivity of direct detection. The addition of sheep blood to liquid culture media increased the Bartonella henselae DNA concentration compared to controls, additionally improving PCR direct detection sensitivity. IMPORTANCE This study aims to improve diagnostic detection of Bartonella henselae. Patient samples are combined with enriched bacterial cultures aimed at growing Bartonella henselae for the best possible chance at detection. However, current Bartonella growth methods could be improved. The DNA extraction method used by most laboratories should also be optimized. Sheep blood was added to increase the growth of Bartonella henselae and multiple DNA extraction methods were to be compared to each other.

Diagnosis, Prognosis, and Treatment of Canine Hemangiosarcoma: A Review Based on a Consensus Organized by the Brazilian Association of Veterinary Oncology, ABROVET

Hemangiosarcoma is a mesenchymal neoplasm originating in the endothelial cells of blood vessels; they can be classified as non-visceral and visceral types. Non-visceral hemangiosarcomas can affect the skin, subcutaneous tissues, and muscle tissues; visceral hemangiosarcomas can affect the spleen, liver, heart, lungs, kidneys, oral cavity, bones, bladder, uterus, tongue, and retroperitoneum. Among domestic species, dogs are most affected by cutaneous HSA. Cutaneous HSA represents approximately 14% of all HSA diagnosed in this species and less than 5% of dermal tumors, according to North American studies. However, Brazilian epidemiological data demonstrate a higher prevalence, which may represent 27 to 80% of all canine HSAs and 13.9% of all skin neoplasms diagnosed in this species. Cutaneous HSA most commonly affects middle-aged to elderly dogs (between 8 and 15 years old), with no gender predisposition for either the actinic or non-actinic forms. The higher prevalence of cutaneous HSA in some canine breeds is related to lower protection from solar radiation, as low skin pigmentation and hair coverage lead to greater sun exposure. Actinic changes, such as solar dermatosis, are frequent in these patients, confirming the influence of solar radiation on the development of this neoplasm. There are multiple clinical manifestations of hemangiosarcoma in canines. The diagnostic approach and staging classification of cutaneous HSAs are similar between the different subtypes. The definitive diagnosis is obtained through histopathological analysis of incisional or excisional biopsies. Cytology can be used as a presurgical screening test; however, it has little diagnostic utility in cases of HSA because there is a high risk of blood contamination and sample hemodilution. Surgery is generally the treatment of choice for dogs with localized non-visceral HSA without evidence of metastatic disease. Recently, electrochemotherapy (ECT) has emerged as an alternative therapy for the local ablative treatment of different neoplastic types; the use of radiotherapy for the treatment of dogs with cutaneous HSA is uncommon. There is greater consensus in the literature regarding the indications for adjuvant chemotherapy in subcutaneous and muscular HSA; doxorubicin is the most frequently used antineoplastic agent for subcutaneous and muscular subtypes and can be administered alone or in combination with other drugs. Other therapies include antiangiogenic therapy, photodynamic therapy, the association of chemotherapy with the metronomic dose, targeted therapies, and natural products. The benefits of these therapies are presented and discussed. In general, the prognosis of splenic and cardiac HSA is unfavorable. As a challenging neoplasm, studies of new protocols and treatment modalities are necessary to control this aggressive disease.

Feeding on a Bartonella henselae Infected Host Triggers Temporary Changes in the Ctenocephalides felis Microbiome

The effect of Bartonella henselae on the microbiome of its vector, Ctenocephalides felis (the cat flea) is largely unknown, as the majority of C. felis microbiome studies have utilized wild-caught pooled fleas. We surveyed the microbiome of laboratory-origin C. felis fed on B. henselae-infected cats for 24 h or 9 days to identify changes to microbiome diversity and microbe prevalence compared to unfed fleas, and fleas fed on uninfected cats. Utilizing Next Generation Sequencing (NGS) on the Illumina platform, we documented an increase in microbial diversity in C. felis fed on Bartonella-infected cats for 24 h. These changes returned to baseline (unfed fleas or fleas fed on uninfected cats) after 9 days on the host. Increased diversity in the C. felis microbiome when fed on B. henselae-infected cats may be related to the mammalian, flea, or endosymbiont response. Poor B. henselae acquisition was documented with only one of four infected flea pools having B. henselae detected by NGS. We hypothesize this is due to the use of adult fleas, flea genetic variation, or lack of co-feeding with B. henselae-infected fleas. Future studies are necessary to fully characterize the effect of endosymbionts and C. felis diversity on B. henselae acquisition.

The association of host and vector characteristics with Ctenocephalides felis pathogen and endosymbiont infection

Surveillance of the fleas and flea-borne pathogens infecting cats is important for both human and animal health. Multiple zoonotic Bartonella and Rickettsia species are known to infect the most common flea infesting cats and dogs worldwide: Ctenocephalides felis, the cat flea. The ability of other flea species to transmit pathogens is relatively unexplored. We aimed to determine cat host and flea factors independently associated with flea Bartonella and Rickettsia infection. We also assessed flea and cat infection by flea-host pair and location. To accomplish these aims, we performed qPCR for the detection of Bartonella, hemotropic Mycoplasma, Rickettsia, and Wolbachia DNA using paired cat and flea samples obtained from free-roaming cats presenting for spay or neuter across four locations in the United States. A logistic regression model was employed to identify the effect of cat (sex, body weight, geographic location, and Bartonella, hemotropic Mycoplasma, and Rickettsia spp., infection) and flea (clade and Rickettsia and Wolbachia infection) factors on C. felis Bartonella clarridgeiae infection. From 189 free roaming cats, we collected 84 fleas: Ctenocephalides felis (78/84), Cediopsylla simplex (4/84), Orchopeas howardi (1/84), and Nosopsyllus fasciatus (1/84). Ctenocephalides felis were phylogenetically assigned to Clades 1, 4, and 6 by cox1 gene amplification. Rickettsia asembonensis (52/84) and B. clarridgeiae (16/84) were the most common pathogenic bacteria detected in fleas. Our model identified host cat sex and weight as independently associated with B. clarridgeiae infection in fleas. Rickettsia asembonensis (52/84), Rickettsia felis (7/84) and Bartonella henselae (7/84) were detected in specific clades: R. felis was detected only in Clades 1 and 6 while B. henselae and R. asembonensis were detected only in Clade 4. Wolbachia spp., also displayed clade specificity with strains other than Wolbachia wCfeT only infecting fleas from Clade 6. There was poor flea and host agreement for Bartonella spp., infection; however, there was agreement in the Bartonella species detected in cats and fleas by geographic location. These findings reinforce the importance of considering reservoir host attributes and vector phylogenetic diversity in epidemiological studies of flea-borne pathogens. Widespread sampling is necessary to identify the factors driving flea-borne pathogen presence and transmission.

Molecular Survey of Bartonella Species in Stray Cats and Dogs, Humans, and Questing Ticks from Portugal

Bartonella spp. comprises emergent and re-emergent fastidious Gram-negative bacteria with worldwide distribution. Cats are the main reservoir hosts for Bartonella henselae and dogs represent opportunistic hosts for the bacteria. Even though ticks may also play a role in transmission, their competence as vectors for Bartonella spp. has not been totally understood. Considering only a few studies had a focus on screening Bartonella in animals, humans and ectoparasites in Portugal, this study aimed to address the molecular occurrence of Bartonella sp. in 123 stray cats, 25 stray dogs, 30 humans from Lisbon and 236 questing ticks within the country. Using a qPCR targeting the nuoG gene, it was possible to detect Bartonella sp. DNA on 20.32% of cat samples (25/123). From these positive samples, 13 sequences were characterized as B. henselae, 11 as B. clarridgeiae and 1 presented co-infection with both species. The absolute quantification of nuoGBartonella DNA in sampled cats ranged from 2.78 × 10 to 1.03 × 10⁵ copies/µL. The sampled dogs, humans and ticks were negative. These results showed that B. henselae and B. clarridgeiae are circulating in stray cats from Lisbon. Additional and more extended studies should be conducted to determine the impact of such infections on humans, particularly those in constant and direct contact with cats.

Bartonella henselae Recombinant Pap31 for the Diagnosis of Canine and Human Bartonelloses

Bartonella spp. comprise a genus of Gram-negative alphaproteobacteria that are slow growing, fastidious, and facultative intracellular pathogens with zoonotic potential. Immunofluorescent antibody assays (IFAs), Western blot (WB), and enzyme-linked immunosorbent assays (ELISAs), the frequently used modalities for the serological diagnosis of canine and human Bartonelloses, generate numerous false negative results. Therefore, the development of a reliable serodiagnostic assay for Bartonelloses is of clinical and epidemiological importance. Pap31, a heme binding surface protein of B. henselae, is associated with bacterial adhesion and related to bacterial colonization. To our knowledge, B. henselae Pap31 and its fragments (N-terminal (NTD), middle (MD), and C-terminal (CTD) domains) have not been investigated for the serodiagnosis of canine and human Bartonelloses. In this study, we evaluate the diagnostic utility of B. henselae recombinant whole Pap31 (rPap31) and Pap31 fragments by ELISA using sera from 70 dogs (36 Bartonella spp. IFA-positive (naturally infected), and 34 Bartonella spp. IFA- and PCR-negative (control dogs)) and 36 humans (18 Bartonella spp. IFA-positive (naturally infected) and 18 controls)). In the dogs, the area under the curve (AUC) score of recombinant whole Pap31 was 0.714 with a sensitivity of 42% and specificity of 94% at an OD cutoff value of 0.8955. Among the evaluated recombinant Pap31 proteins for the diagnosis of canine Bartonelloses, rPap31-NTD yielded the highest AUC score of 0.792 (95% CI 0.688-0.895) with a sensitivity of 44% and specificity of 100% at a cutoff value of 1.198. In concordance with this finding, rPap31-NTD also had the highest AUC score of 0.747 (95% CI 0.581-0.913) among the Pap31 recombinant proteins for the diagnosis of human Bartonelloses, with 39% sensitivity and 94% specificity at a cutoff value of 1.366. Recombinant whole Pap31 (rPap31) resulted in 72% sensitivity and 61% specificity at a cutoff value of 0.215 for human Bartonelloses. Due to either low sensitivity or questionable specificity, our findings indicate that recombinant Pap31 and the selected fragments may not be appropriate diagnostic targets in detecting anti-Bartonella antibodies in Bartonella-infected dogs and humans. The findings from this study can be used to further assess the antigenicity and immunogenicity of B. henselae Pap31 as a diagnostic target.