More than happenstance: Creutzfeldt-Jakob disease in farmers and young adultsBMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7017.1416a (Published 25 November 1995) Cite this as: BMJ 1995;311:1416
- Sheila M Gore, senior statisticiana
- aMRC Biostatistics Unit, Institute of Public Health, Cambridge CB2 2SR
In 1986, four years after a change in the processing of offals--including those from sheep infected with scrapie--into cattle meal, the first British case of bovine spongiform encephalopathy was confirmed.
Median incubation period in cattle is around four to five years.1 By 14 April 1995, bovine spongiform encephalopathy had been confirmed in 53.3% of dairy herds, 14.7% of beef suckler herds, and 33.8% of all herds with adult breeding cattle; people who work on farms without confirmed cases of bovine spongiform encephalopathy may, however, have worked on farms with infected, but not affected, cattle. The aim of ongoing studies in cattle is to find evidence of direct transmission of bovine spongiform encephalopathy by the two suggested means of transmission of scrapie in sheep: from mother to offspring or between unrelated animals around parturition.
The incubation period of human spongiform encephalopathies--kuru and Creutzfeldt-Jakob disease--is poorly estimated from data2 but is apparently in the range 15-40 years, possibly shorter in people who were young at exposure. The potential for the agent responsible for bovine spongiform encephalopathy to cross species barriers after occupational or dietary exposure--including exposure to cattle meal by ingestion or inhalation--has been a major concern for human health. Whether the agent is pathogenic to humans cannot be known by direct experimentation. Thus, surveillance of cases of sporadic Creutzfeldt-Jakob disease--in terms of occupational distribution, temporal changes in incidence, and dietary correlations--is the only way to get early warning of pathogenesis of bovine spongiform encephalopathy in humans. British surveillance of Creutzfeldt-Jakob disease was therefore reactivated in May 1990,3 and a grant from the European Community in 1993 enabled surveillance projects elsewhere in Europe to share common diagnostic criteria, methodologies, and casecontrol questionnaires. Two observations from …