1998 J Dairy Sci 81:3042–3048 3042 Received June 23, 1997. Accepted December 15, 1997. Bovine Spongiform Encephalopathy: Current Status and Possible Impacts J. ERIC HILLERTON Institute for Animal Health, Compton, Newbury, Berks, United Kingdom RG20 7NN ABSTRACT Bovine spongiform encephalopathy is an appar- ently new disease; first recognized in 1985, its patho- logical distinction was first reported in 1986. Bovine spongiform encephalopathy is a member of a group of transmissible encephalopathies that includes scrapie in sheep and Creutzfeldt-Jakob Disease in humans. Early indications of its epidemiology suggested that the disease was transmitted via cattle feed containing meat and bone meals from previously infected animals. The tissues most likely to contain infectious agents were considered to be nervous tissues and offal, and their inclusion in ruminant feed was banned in the United Kingdom in 1989; regulations were tightened in 1992. Subsequent diagnosis has indicated that this ban has been effective and that confirmed cases are predicted to decline from a peak in the United Kingdom of 37,490 in 1992, to 7417 actual cases in 1996, and then to virtual extinction in 2001. Subsequent culling of all nonproductive cattle more than 30 mo of age and culling of cohort animals of confirmed cases is likely to reduce the predicted numbers and times significantly. Current interest is in the means of transmission of bovine spongiform encephalopathy within species and possibly to hu- mans. A new variant of Creutzfeldt-Jakob Disease, with 28 cases confirmed, is virtually certain to be bovine spongiform encephalopathy in humans. The outbreak of bovine spongiform encephalopathy has had major impacts on the United Kingdom dairy in- dustry, including the loss of beef from dairy markets, the culling of more than 900,000 dairy bull calves, the removal of all cattle more than 30 mo of age from the human food chain, and now slaughter of cohort animals. Impacts on dairy marketing have yet to be properly assessed. Information and statistics for bovine spongiform encephalopathy can be found on the worldwide web at http://www.maff.gov.uk/maffhome.html. ( Key words: bovine spongiform encephalopathy, Creutzfeldt-Jakob disease, nvCJD, transmissible spongiform encephalopathies) Abbreviation key: BSE = bovine spongiform en- cephalopathy, CJD = Creutzfeldt-Jakob disease, nvCJD = new variant of CJD, OTMS = Over Thirty Months Scheme, TSE = transmissible spongiform en- cephalopathies, UK = United Kingdom. INTRODUCTION Transmissible spongiform encephalopathies ( TSE) are neurodegenerative diseases that are known for at least 12 different species of animals. The best under- stood is scrapie in sheep, first described in 1732, for which more than 20 different strains have been recog- nized by passage in mice. A number of encephalo- pathies affect humans. The most widely known, kuru, affects the Fore tribe of New Guinea (12); the trans- mission of kuru has been associated with endocan- nibalism, especially of the brain, of dead relatives by females and young children. There has been no trans- mission of the diseases directly to offspring, no associ- ation with pregnancy, and no indication that lactation is involved. No child born since cannibalism ceased has developed the disease. Creutzfeldt-Jakob disease ( CJD) is more widespread, and four forms are recog- nized. Occurrence of CJD is generally rare and occurs in countries where no animal TSE are known. There are several inherited or familial variants (27). Kuru is an acquired CJD. Iatrogenic cases arise from infec- tion via routes such as hormone therapy or corneal grafts (22). Most cases are sporadic with no known etiology, but the incidence of disease appears to be influenced by genotype (18). There is no obvious risk associated with country of residence or occupation in the development of sporadic CJD. Encephalopathy in cattle was first described in 1986 (24) in the United Kingdom ( UK) , following recognition of a new clinical syndrome in 1985. This bovine spongiform encephalopathy ( BSE) has had a major effect on the UK cattle industry and has now been shown to be extremely similar to a new variant of CJD in man, nvCJD (26). Significant advances
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