Abstract
This paper questions the conventional wisdom that spongiform encephalopathies, particularly bovine spongiform encephalopathy (BSE), are solely due to ‘infection’ with an ultrafiltrable particulate protein called a prion. The literature is reviewed and data and circumstantial evidence are presented to support the hypothesis that the BSE epidemic was initiated as a result of a combination of factors—genetic, nutritional and chronic exposure to mutagenic organophosphate pesticides which disrupt the genetic pathway of prion protein synthesis. Possible mechanisms are discussed and the broader implications for modern farming practices inspected.