Bartonella henselae, Bartonella koehlerae and Rickettsia rickettsii seroconversion and seroreversion in a dog with acute-onset fever, lameness, and lymphadenopathy followed by a protracted disease course

Following recent tick exposure in Arkansas, a 2-year-old, female spayed Labradoodle was examined because of a one-week history of lethargy and shifting-leg lameness. The dog was febrile, had prominent lymph nodes, dull mentation, a stiff gait, and left forelimb lameness. Thrombocytopenia was the only initial hematological or biochemical abnormality. Despite treatment with doxycycline for suspected Rocky Mountain spotted fever, the dog continued to have waxing and waning clinical signs including inappetence, fever, shifting-leg lameness, lymphadenopathy, splenomegaly, and weight loss in association with moderate to severe hematological abnormalities, including anemia, thrombocytopenia, neutrophilia, and monocytosis. Sequential serological testing confirmed Bartonella henselae, Bartonella koehlerae and R. rickettsii seroconversion. Doxycycline, enrofloxacin and clarithromycin were administered in sequential combination for treatment of rickettsioses, B. henselae and B. koehlerae. Prednisone, thyroid supplementation and other drugs were administered to elicit symptomatic improvement. Based upon seroreversion, and the eventual resolution of all clinical and hematological abnormalities, therapeutic elimination of all three pathogens was seemingly achieved. Whether cortisol insufficiency due to adrenal exhaustion syndrome or post-infectious immune-mediated sequelae contributed to the symptoms and pathophysiological abnormalities reported in this dog was not determined, but are considerations for future cases.