Myocarditis in a Dog Positive for Brucella canis

A 1 yr old female spayed dog presented for evaluation of lethargy, hyporexia, and left hind limb lameness. On presentation, she was tachycardic and febrile. Echocardiogram revealed pericardial effusion and evidence of pericarditis and myocarditis, and electrocardiogram showed underlying sinus rhythm with complex arrhythmias. Cardiac troponin-I level was markedly elevated. The dog was hospitalized for 6 days on IV fluid therapy and treated with ampicillin/sulbactam and enrofloxacin. She was discharged on amoxicillin-clavulanic acid and maropitant citrate. Within 24 hr, the dog returned because of progressive clinical signs. It was revealed that two of her littermates had tested positive for Brucella canis, so antimicrobial therapy was switched to enrofloxacin and doxycycline. Six days later, the dog developed worsening clinical signs and was euthanized. Postmortem examination was performed. Blood cultures and brucellosis testing were positive for B canis. Two other dogs and two humans in the household were ultimately diagnosed with brucellosis. To our knowledge, infection with B canis has not been reported in dogs diagnosed with myocarditis. However, myocarditis is a rare clinical manifestation of brucellosis in humans. Depending on patient history, clinical signs, and diagnostic findings, brucellosis is a zoonotic disease that may be a differential diagnosis in dogs with suspected myocarditis.