Mitral endocarditis secondary to Listeria monocytogenes in a dog

A Beauceron was evaluated for a 3-week history of unresponsive immune-mediated polyarthritis and meningitis. Physical examination revealed a previously unreported grade III/VI left apical systolic heart murmur. Based on the echocardiographic examination and blood culture, a diagnosis of mitral valve infective endocarditis secondary to Listeria monocytogenes was made. Despite extensive workup, no definitive primary focus of infection was identified in this case. The endocarditis was suspected to have triggered secondary immune-mediated polyarthritis and meningitis. The dog was treated with empirical antimicrobial combination therapy and immunosuppressives, and fully recovered from infection. No relapse was documented 5 months after discontinuation of treatment. Cardiomegaly secondary to persistent mitral regurgitation had developed. This is the first description of endocarditis secondary to L. monocytogenes in a dog.