Bovine spongiform encephalopathy and a new variant of Creutzfeldt-Jakob disease.

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The transmissible spongiform encephalopathies are a large group of neurodegenerative disorders that affect both humans and animals. [1] The transmissible agent has been identified as an isoform of a normal brain protein PrPc designated PrP sup sc, or the prion protein. [2] These disorders have common pathologic features, including, as the name implies, spongiform change in the brain associated with astrogliosis, neuronal loss, and the deposition of proteinase-resistant amyloid protein (PrP) in brain plaques, usually with a characteristic distribution. In humans, the most common spongiform encephalopathy, Creutzfeldt-Jakob disease (CJD), occurs sporadically with a frequency of approximately one case per million population per year. [1] In addition, there are a number of genetically determined forms of spongiform encephalopathy caused by mutations in the PrP gene. [1,3] The transmissibility of scrapie between sheep with use of nervous tissue was reported as early as 1936 in France. [4] Pathologic similarities between scrapie in sheep and kuru in humans were noted by Hadlow in 1959. [5] Landmark experiments by Gajdusek and colleagues [6,7] demonstrated the transmissibility of CJD and kuru to a number of nonhuman primate and other mammalian hosts. Human-to-human transmission was described for kuru associated with ritualistic cannibalism in the highlands of New Guinea [6] and a number of iatrogenic transmissions were described in association with corneal and dura mater transplants, inadequately sterilized neurosurgical instruments, and contaminated growth hormone prepared from cadaveric pituitary tissue. [1] The appearance in 1986 of a new spongiform encephalopathy in British cattle, bovine spongiform encephalopathy (BSE), [8] raised the concern of possible transmission of this disorder to the human population by consumption of beef or other tissues from infected cattle. This concern was, in part, balanced by the knowledge that scrapie-infected sheep in large numbers had been consumed for many decades with no documented transmission of …