The research programme on transmissible spongiform encephalopathies in Britain with special reference to bovine spongiform encephalopathy.

Research into bovine spongiform encephalopathy (BSE) commenced immediately following its discovery in November 1986. Formal epidemiological studies commenced in June 1987 and were part of a large research programme set up mainly at the Central Veterinary Laboratory Weybridge and the Institute for Animal Health, AFRC/MRC Neuropathogenesis Unit in Edinburgh. This programme also covered the clinicopathology of BSE, transmission studies and molecular chemistry. Research results have shown that BSE is a member of the group of diseases known as the sub-acute spongiform encephalopathies caused by unconventional transmissible agents and which includes scrapie of sheep, from which BSE was probably derived, and Creutzfeldt Jakob disease (CJD) of man. The agent causing BSE closely resembles strains of the scrapie agent but is not identical. Spongiform encephalopathy has developed in sheep, goats, pigs, cattle, marmosets and mice but not hamsters following experimental inoculation of brain material from confirmed clinical cases of BSE. BSE agent has been detected by mouse bio-assay in brain from cows from several sources confirmed to have BSE. Infectivity has not been detected in spleen, buffy coat, semen, muscles, placenta and bone marrow (all following parenteral inoculation) nor in milk/mammary gland, spleen, placenta and a variety of lymph nodes following substantial oral exposure. This latter route successfully transmitted disease to mice with brain/cerebrospinal fluid. The introduction of modified rendering systems, which did not employ hydrocarbon solvent extraction, were probably responsible for an increase in exposure of cattle from 1981-1988 sufficient to cause the disease. Experiments are in progress to investigate the effectiveness of different rendering systems used in the European Community and of chemical and physical de-activating procedures for destroying BSE and scrapie infectivity. A clear genetic influence on disease susceptibility has been suggested but is not yet proven. The Agricultural and Food Research Council have set up a large Biology of Spongiform Encephalopathies Research Programme to address some of the more fundamental unknowns of this group of diseases but it is too early to report results. As with scrapie, no epidemiological relationship has been demonstrated between BSE and the human diseases through the monitoring programme that has been established by the Department of Health to detect such an occurrence. BSE research results so far show that controls to protect animal and human health and based initially on scrapie research findings, are sound.(ABSTRACT TRUNCATED AT 400 WORDS)