Three consecutive cases of rhinocerebral mucormycosis in calves caused by Lichtheimia ramosa infection on a beef cattle farm.

Three Japanese Black calves died within a two-month period on a beef cattle farm. Necropsy consistently revealed liquefactive necrosis of the ventral brain (extending from the olfactory bulb to the midbrain) and thymic atrophy. Histopathologically, necrosuppurative encephalitis characterized by abundant fungal hyphae was observed in all three cases. Fungal lesions also involved the olfactory mucosa, olfactory nerves, and olfactory bulb. Fungi isolated from the cerebrum of all three calves were identified as Lichtheimia ramosa. These cases were diagnosed as rhinocerebral mucormycosis, originating in the olfactory mucosa and extending to the cerebrum. Although mucormycosis is typically sporadic, this report documents the first occurrence of consecutive cases of bovine rhinocerebral mucormycosis caused by L. ramosa.