Bovine spongiform encephalopathy: epidemiological studies on the origin

Area of Science:

• Veterinary epidemiology
• Animal prion diseases
• Food safety science

Background:

• Bovine spongiform encephalopathy (BSE) is a fatal neurodegenerative disease in cattle.
• Previous studies suggested a link between BSE onset and changes in animal feed production.
• Understanding the precise timing and sources of BSE exposure is crucial for disease control.

Purpose of the Study:

• To further investigate the epidemiological timeline of BSE exposure in cattle.
• To identify specific changes in rendering processes that may have initiated BSE transmission.
• To explore factors contributing to the geographical distribution of BSE cases.

Main Methods:

• Analysis of epidemiological data on BSE incidence in cattle populations.
• Correlation of BSE onset dates with historical changes in rendering plant operations, specifically fat extraction methods.
• Examination of geographical variations in BSE occurrence in relation to reprocessing of specific feed components (greaves).

Main Results:

• Epidemiological findings confirm the onset of significant cattle exposure to a scrapie-like agent occurred around 1981/82.
• This exposure period coincided with the discontinuation of hydrocarbon solvent extraction for fat from meat and bone meal in most rendering facilities.
• Geographical variations in BSE incidence were potentially explained by differences in the reprocessing of greaves.

Conclusions:

• The findings support 1981/82 as the critical period for BSE agent exposure in cattle.
• Changes in rendering practices, particularly the cessation of solvent extraction, are strongly implicated in the BSE epidemic's initiation.
• Variations in reprocessing greaves may explain the observed geographical patterns of BSE incidence.