Pituitary abscess, plexus-choroiditis and encephalitis by Helcococcus ovis in a calf.

We report here the first confirmed case of a pituitary abscess in a calf caused by Helcococcus ovis, an emerging pyogenic bacterium in veterinary medicine. An 8-month-old calf showed progressive neurological signs following the use of a nose ring. Gross and histopathological examination revealed a large abscess in the pituitary gland accompanied by leptomeningitis, encephalitis, and plexus choroiditis. Helcococcus ovis was isolated from the pituitary abscess and identified by MALDI-TOF mass spectrometry with high confidence. Coccoid gram-positive bacteria were observed on gram stain of formalin-fixed tissues from leptomeningitis, plexus choroiditis and pituitary abscess lesions. Gross and histological features were indistinguishable from abscesses caused by other pyogenic organisms, highlighting the critical importance of bacteriological culture to diagnosis. This case expands the known pathogenic spectrum of H. ovis and suggests its inclusion in the differential diagnosis of suppurative central nervous system lesions in cattle.