Bartonella henselae in canine cavitary effusions: prevalence, identification, and clinical associations

Previous reports suggest an association between Bartonella infection and effusions in dogs and human beings.

The aims of this study were to determine the prevalence of Bartonella infection in canine effusions and to investigate historic and clinical parameters predictive of Bartonella in dogs with effusions.

Canine cavitary effusions submitted for analysis and, if available, paired EDTA blood, were screened for Bartonella infection using the Bartonella α-proteobacteria growth medium enrichment culture/PCR diagnostic platform (Bartonella enrichment PCR or ePCR) at Galaxy Diagnostics, Inc.

Bartonella henselaeDNA was PCR-amplified and sequenced from 15% (12/80) of sampled dogs. Enrichment culture prior to PCR testing was required for Bartonella detection in 92% (11/12) of cases. Twenty percent (4/20), 13% (8/60), and 0% (0/4) of dogs with pleural, peritoneal, and pericardial effusions, respectively, tested positive. Bartonella henselae was detected most frequently in the fall, and young and middle-aged dogs appeared to be overrepresented. Golden Retrievers and Yorkshire/Silky Terriers each comprised 25% of infected dogs (odds ratio 3.4 for Golden Retrievers). There was a weak association with hemorrhagic effusions. Fifty percent of Bartonella-positive dogs had hemorrhage as a component of their effusion compared to 37% of PCR-negative dogs (odds ratio 1.7).

Viable B henselae organisms occur in pleural and peritoneal effusions of dogs; the clinical relevance of which remains unclear and may represent opportunistic infection. Associations found in this study included seasonal variation, age, breed, and site of effusion.