Detection of Bartonella henselae DNA 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], PO, q 12 h), whereas the other dog recovered after receiving a combination of azithromycin (14.5 mg/kg [6.6 mg/lb], PO, q 24 h for 21 days), doxycycline (17.3 mg/kg [7.9 mg/lb], PO, q 24 h for 4 weeks), and immunosuppressive corticosteroid (prednisone [3 mg/kg {1.4 mg/lb}, PO, 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.