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

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.