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Bovine spongiform encephalopathy

Bovine spongiform encephalopathy is a neurodegenerative disorder which belongs to transmissible spongiform encephalopathy. It affects mainly cattle as well as goat, captive wild ungulate, captive wild cats and domestic cats naturally. Since the first identification in 1986 in UK, about 190,000 cases have been reported in 21 European countries, Israel, Japan, Canada and USA up to date. The mean incubation period of BSE in naturally infected cattle was estimated at about 5 years with a variance of about 1.6 years and only 54 cases occurred in cattle under 30 months of age up to now. BSE is believed to be caused by PrPsc, a disease causing isoform of PrPc which is a normal cell surface protein. In 1996, a possible link between BSE and variant Creutzfeldt-Jakob disease was suggested and BSE became a zoonosis. Currently, about 200 cases of variant Cretutzfeldt-Jakob Disease (vCJD) have been identified worldwide. BSE is transmitted via feeding meat and bone meal. The pathogenesis of BSE is still unclear, but central nervous system and distal ileum are first involved, whilst peripheral nervous system is involved much later. BSE is believed to be caused by a single strain (C-type), but recently challenged by identification of atypical BSE cases (H-type : 16, L-type : 19) in Europe, Japan and North America. More research on atypical BSE need to be conduct to determine whether the isolates are strains of BSE, or different prion diseases of bovines.