Vegetative Valvular Endocarditis and Hepatitis Associated with Helcococcus ovis in a 7-year-old White Leghorn Rooster

Helcococcus ovis is a slow-growing, pyridoxal-dependent, Gram-positive coccus belonging to the Peptostreptococcaceae family. Bacteria belonging to the genus Helcococcus are considered normal inhabitants of keratinized epithelium in humans; however, several reports support their role as pathogens in humans and several animal species. This case report describes the identification of H. ovis in a white leghorn rooster with valvular vegetative endocarditis and hepatitis. In February 2017 one dead, 7-yr-old, white leghorn rooster was submitted to the California Animal Health and Food Safety Turlock laboratory for diagnostic testing. Postmortem and microscopic examination revealed vegetative endocarditis and aortic thrombosis associated with large numbers of Gram-positive cocci. Myocarditis and extensive necrotic hepatitis were also noticed. Helcococcus ovis was isolated in large numbers from the aortic endothelium and confirmed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Bacterial colonies become evident 48 hr postincubation and exhibited a satellite growth around Escherichia coli on blood agar plates. A similar relationship has been described between Helcococcus spp. and Staphylococcus aureus. The primary site of infection in this chicken was not determined. To our understanding this is the first report of H. ovis infection in an avian species. The fastidious nature and nutritional requirements of Helcococcus spp. must be considered in order to allow proper identification and avoid misdiagnosis. Further studies are needed to define pathogenesis, virulence factors, and predisposing conditions associated with this microorganism.