Molecular prevalence of Bartonella, Babesia, and hemotropic Mycoplasma species in dogs with hemangiosarcoma from across the United States.

Erin Lashnits,Toni Richardson,Matthew Breen,Ricardo G Maggi,Edward B Breitschwerdt,Keith E Linder,Julie M Bradley,Rachael Thomas,Pradeep Neupane,Douglas H Thamm

doi:10.1371/journal.pone.0227234

Abstract

Hemangiosarcoma (HSA), a locally invasive and highly metastatic endothelial cell neoplasm, accounts for two-thirds of all cardiac and splenic neoplasms in dogs. Bartonella spp. infection has been reported in association with neoplastic and non-neoplastic vasoproliferative lesions in animals and humans. The objective of this study was to determine the prevalence of Bartonella spp. in conjunction with two other hemotropic pathogens, Babesia spp. and hemotropic Mycoplasma spp., in tissues and blood samples from 110 dogs with histopathologically diagnosed HSA from throughout the United States. This was a retrospective, observational study using clinical specimens from 110 dogs with HSA banked by the biospecimen repository of the Canine Comparative Oncology and Genomics Consortium. Samples provided for this study from each dog included: fresh frozen HSA tumor tissue (available from n = 100 of the 110 dogs), fresh frozen non-tumor tissue (n = 104), and whole blood and serum samples (n = 108 and 107 respectively). Blood and tissues were tested by qPCR for Bartonella, hemotropic Mycoplasma, and Babesia spp. DNA; serum was tested for Bartonella spp. antibodies. Bartonella spp. DNA was amplified and sequenced from 73% of dogs with HSA (80/110). In contrast, hemotropic Mycoplasma spp. DNA was amplified from a significantly smaller proportion (5%, p<0.0001) and Babesia spp. DNA was not amplified from any dog. Of the 100 HSA tumor samples submitted, 34% were Bartonella PCR positive (32% of splenic tumors, 57% of cardiac tumors, and 17% of other tumor locations). Of 104 non-tumor tissues, 63% were Bartonella PCR positive (56% of spleen samples, 93% of cardiac samples, and 63% of skin/subcutaneous samples). Of dogs with Bartonella positive HSA tumor, 76% were also positive in non-tumor tissue. Bartonella spp. DNA was not PCR amplified from whole blood. This study documented a high prevalence of Bartonella spp. DNA in dogs with HSA from geographically diverse regions of the United States. While 73% of all tissue samples from these dogs were PCR positive for Bartonella DNA, none of the blood samples were, indicating that whole blood samples do not reflect tissue presence of this pathogen. Future studies are needed to further investigate the role of Bartonella spp. in the development of HSA.

Highlights

There are clear precedents for the involvement of bacterial infection in neoplastic development
[22] We found that Bartonella spp. were significantly more common than Babesia spp. or hemotropic Mycoplasma spp. in formalin-fixed, paraffin embedded biopsy samples from splenic HSA: 26% of dogs were positive for Bartonella spp. compared to 2% for Babesia spp. (p < 0.001) and 6% for hemotropic Mycoplasma spp. (p = 0.006)
Consistent with our previous study,[22] the proportion of Bartonella spp. infection in dogs with HSA was significantly greater than the proportion of Babesia or hemotropic Mycoplasma spp

Summary

Introduction

There are clear precedents for the involvement of bacterial infection in neoplastic development. [1,2] Currently, infectious agents are accepted as a cause or co-factor in anywhere from 5–50% of human cancers worldwide, depending on the geographic region and its development status. [1,2,3] The involvement of infectious agents in the pathogenesis of some human cancers is well established. The majority of infectious agents implicated in oncogenesis are viruses, such as Epstein Barr virus, human papillomaviruses, and Kaposi’s sarcoma-associated herpesvirus.[1] These viruses have direct oncogenic properties through integration of viral genomes into host cells, or by secretion of gene products into healthy cells to create tumor cells. The extent to which other infectious agents, such as bacteria, lack the inherent oncogenic properties of their viral counterparts remains unclear. With the difficulty of assessing causality, for certain rare cancer types, there may be roles for other pathogenic bacteria in a range of different cancers that have not yet been discovered.[7]

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