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Bovine spongiform encephalopathy (BSE) is a transmissible neurodegenerative disease. Six brain regions from 11 cattle were examined for the presence of the abnormal isoform of the prion protein (PrPBSE). The highest concentrations of PrPBSE were found in the brain stem, where the greatest degree of spongiform change was observed. Molecular cloning of the bovine PrP gene showed that it encodes a protein of 256 or 264 amino acids with five or six Gly:Pro-rich octarepeats, respectively, in contrast to all other mammalian PrP genes, which encode only five octarepeats. The bovine PrP gene is single copy, and the entire open-reading frame lies within a single exon. Since the transmission of prions across species seems to be restricted by differences in PrP sequence, the high degree of homology between sheep and bovine PrP (98%) correlates with the proposed cause of BSE.

Listeria monocytogenes type 4 was isolated from milk of a cow affected with mastitis in the left fore quarter. Histological examination revealed a severe suppurative mastitis with eosinophil leucocytes predominating among the inflammatory cells. The findings and the public health aspect of the condition are discussed.

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BSE is a new disease of cattle. The first clinical case occurred in April 1985 but the existence of a new disease was first confirmed microscopically in November 1986. Epidemiological studies show that cattle suddenly became effectively exposed to a scrapie-like agent in ruminant-derived feed in the form of meat and bone meal in 1981/2. Most cases have occurred in Holstein Friesian dairy cattle and have been exposed as calves. There is no evidence that cattle to cattle transmission sufficient to maintain the epidemic occurs. The principle animal health control measures are bans on the feeding of ruminant derived protein to ruminant animals and on the use of specified bovine offals (SBO) for feeding to any species of animal or birds. Human health is protected by compulsory slaughter and destruction of suspect animals, and a ban on the use of their milk, and by prohibiting the use of SBO in food. The SBO are those tissues which, in clinically healthy cattle incubating BSE, might conceivably harbour infectivity. The effectiveness of the bans is supported by recent evidence of a decline in the cattle epidemic. There is no evidence that BSE is a zoonosis.

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