Histological observations on the brains of symptomless 7-year-old cattle

The histological changes in the brains of 506 clinically normal 7-year-old cattle, which were part of a cohort study On maternal transmission of bovin e spongiform encephalopathy, are described. Vacuolation of the white matter . of unknown aetiology, located particularly in the substantia nigra, was a frequent finding. Vacuolated neurons were commonly observed in the red nuc leus (64.3% of the animals) and in the habenular nucleus (50.1%). Spheroids were round in 10.8% of the brains, most frequently in the vestibular nucle i. Cellular inflammatory infiltrates ill association with blood vessels occ urred in 30% of the animals at various locations in the brain; their aetiol ogy remains uncertain, but they may have reflected subclinical or latent in fections. Mineralization of the wall of blood vessels, with proliferation o f the intima, was observed frequently ill vessels of the internal capsule a nd was probably associated with ageing. The description of histological fin dings ill the brain of symptomless adult cattle in the present study provid es a useful background for diagnostic bovine neuropathology. (C) 2001 Harco urt Publishers Ltd.