Reference

The decline in bovine spongiform encephalopathy (BSE) cases over the past few decades can be attributed to several key interventions and measures:

1. Feed Bans: The most critical action was the implementation of bans on feeding cattle meat-and-bone meal (MBM) that included ruminant protein. For instance, the UK imposed such a ban in 1988. This practice had been identified as the primary route of transmission for BSE, as infected material was recycled back into cattle feed, perpetuating the disease cycle.

2. Surveillance and Testing Programs: Comprehensive and rigorous surveillance programs were developed to identify and control BSE occurrences. This included mandatory testing of cattle at slaughter and increased monitoring efforts to ensure that infected animals were identified and removed from the food chain.

3. Culling Infected Animals: Infected herds were culled to prevent the spread of BSE. Continued culling reduced the risk of infected animals entering the food supply or spreading the prion to other cattle.

4. Disposal of Specified Risk Materials: Regulations were put in place to ensure that specified risk materials (SRM) — tissues most likely to carry the infectious prions, such as the brain and spinal cord — were removed and safely disposed of during the slaughtering process.

5. International Cooperation and Standards: Countries worked together through organizations like the World Health Organization (WHO) and the World Organisation for Animal Health (OIE) to establish and adhere to international safety standards. This cooperation facilitated the sharing of data and best practices to control and eradicate BSE globally.

6. Public Awareness and Education: Efforts were made to educate the public and farmers about BSE, its risks, and the measures to control it. This increased awareness helped in the early reporting and handling of potential BSE cases.

Here are a few sources that detail the measures and their impacts:

• USDA - BSE Surveillance Information Center
• Merck Veterinary Manual on BSE
• CDC - Mad Cow Disease

These efforts have led to a dramatic reduction in BSE cases globally. For example, the United States reported only 29 cases worldwide in 2011, representing a 99% reduction from the peak number in 1992, which saw 37,311 cases.

This comprehensive and multi-faceted approach has been crucial in effectively controlling and reducing the incidence of BSE.