Transmittable diseases: the lessons from bovine spongiform encephalopathy (BSE)

Abstract

AbstractBSE was first discovered in November 1986 and by July 1991 about 60 000 cases had been confirmed in Great Britain with a low incidence being reported in Northern Ireland, the Republic of Ireland, Switzerland and France. The origin of the extended common source epidemic appears to have been food containing meat and bone meal which contained the causal agent. Recycling of infected cattle waste was significant in increasing exposure, at least from the time of the first unrecognized clinical appearance of the disease in 1985. Small numbers of five species ofBovidaein British zoos, domestic cats, a puma and a cheetah have also succumbed to a newly described spongiform encephalopathy. It is anticipated that as a result of the imposition of a ruminant food ban in countries affected by BSE new infections from food have ceased and the incidence of BSE will fall to zero provided there is no other source of infection. Effective controls are in place in Great Britain and Northern Ireland to protect animal and public health. These include disease notification, compulsory slaughter of suspect animals and incineration of the carcasses, a ban on the feeding of specified bovine offals from cattle over 6 months of age or protein derived from them to man, or any species of animal or bird, and a ban on the feeding of ruminant protein to ruminant animals. Genetic studies are still in progress but there is no epidemiological evidence supporting breed predisposition and bovine PrP gene polymorphisms have not been linked with disease occurrence. The lessons from BSE include: the need to retain an animal health surveillance system to detect new and emerging diseases; a strong veterinary research base in unconventional agent disease; and a powerful epidemiology discipline with access to computerized data recording systems, analytical and modelling expertise. Major changes to the composition or processing of animal food, particularly that derived from sources which are not natural for the consuming species, should be carefully monitored for safety before being permitted.