Bovine Spongiform Encephalopathy (BSE), while being similar to scrapie and other Transmissible Spongiform Encephalopathies, has some unique epidemiological and disease characteristics. These include risk factors for the development of widespread BSE, transmission patterns between species and impacts of the disease on other species.

British researchers have developed a list of four main risk factors present in the United Kingdom (UK) which may have played a role in the development of the BSE epidemic starting in 1986. These risk factors, based on the theory that BSE originated from rendered scrapied sheep, are:

1-high sheep:cattle ratio

2-endemic sheep scrapie

3-recycling of ruminant protein to ruminants-especially calves fed milk replacer containing meat and bone meal

4-the presence of imported UK cattle and meat and bone meal

Each of these risk factors are discussed in the Qualitative Analysis of BSE Risk Factors in the United States. This analysis was produced by USDA,APHIS,VS and is available through:

Animal Health Information

555 South Howes

Fort Collins, CO 80521

Two main theories of transmission in the cattle population are in vogue. The first, developed by the British epidemiological community, states that rendered product from scrapied sheep was fed as meat and bone meal to cattle and BSE resulted. A second, states that however the BSE agent was introduced into cattle feed, it was recycled through the rendering process.

The impact of BSE on other species such as sheep and goats is evident. One impact is the Food and Drug Administration’s proposal to ban the feeding of rendered offal from adult sheep and goats to ruminants. The public comments have been reviewed and the proposal is being reconsidered based on the comments. No time table has been set for further action.

A second impact is the National Renderers Association has had a voluntary ban on rendered offal from adult sheep being fed to ruminants. Some renderers have ignored this ban, some have strictly abided by the ban while many not rendered any sheep or lamb offal. This has made it difficult for some producers to find slaughter houses which process lamb and cull sheep. Many such affected producers have had to discard offal from their own animals by either burial or burning.

The Voluntary Scrapie Flock Certification Program is the sheep industry’s proactive response to the BSE situation. While the link from scrapie to BSE has not been definitively established, the perceived relationship exists. A program utilizing permanent animal identification, record keeping and monitoring indicates to the public the sheep industry’s commitment to producing a sound, wholesome product.

BSE has its risk factors, potential epidemiological relationships and impacts on other species. The sheep industry has taken a positive step in dealing with the BSE situation in the Voluntary Scrapie Flock Certification Program.