Verrucous endocarditis of the mitral valve caused by Aspergillus fumigatus in a Japanese Black calf.

A one-month-old Japanese Black calf developed depression, a cardiac murmur, and recumbency and was submitted for pathological examination. Necropsy revealed verrucous vegetations on the mitral valve, dark-red discoloration of the middle lung lobe, and yellowish-white gelatinous changes in the adipose tissue surrounding the renal pelvis. Histologically, the vegetations contained septate hyphae with dichotomous (Y-shaped) branching, with concurrent suppurative bronchitis and vasculitis with fungal hyphae in the kidneys and brain, accompanied by renal infarction. Immunohistochemistry confirmed that the fungus belonged to the genus Aspergillus. A filamentous fungus was isolated from the cardiac vegetation, and β-tubulin gene sequencing identified Aspergillus fumigatus. The calf was diagnosed with systemic aspergillosis associated with A. fumigatus verrucous endocarditis, a rare condition in cattle.