Idiopathic disseminated intracytoplasmic neuronal vacuolation in a neonatal Holstein calf born in the USA

National Animal Disease Center, ARS, USDA, Ames, IA 50010, USA. Histopathologic, immunohistochemical, and ultrastructural evaluations were made of a 6-day-old Holstein calf with severe vacuolation of the neuronal perikarya that was widely distributed throughout the central nervous system. No evidence of storage material within the vacuoles was revealed by histopathologic and ultrastructural examinations. Immunohistochemical and electron microscopic examinations were negative for protease-resistant prion protein and scrapie-associated fibrils, respectively. These results indicate that the clinical signs in this calf were not associated with transmissible spongiform encephalopathy. Neuronal vacuolation has not previously been documented in calves.