Around one hundred BSE infected animals will have been slaughtered for human consumption in France during 2000, an Imperial College statistician has estimated. Dr Christl Donnelly, Department of Infectious Disease Epidemiology, analysed BSE-incidence data from the French Ministry of Agriculture and Fisheries, combined with information from the UK epidemic, to estimate the size and course of the epidemic there. Her results are published today in the journal Nature.
Dr Donnelly found that at least 1,200 French cattle have been infected with the agent that causes BSE since mid-1987 from which she estimates that 49 infected animals will have been slaughtered for human consumption in France during 2000.
She writes: " The risk of BSE entering the food chain from British beef has been markedly reduced now that cattle slaughtered for consumption are restricted to those under 30 months old, but more late-stage infected animals are likely to have been slaughtered for meat this year in France, where no age restriction for slaughter has been imposed."
Dr Donnelly obtained a good fit to the age-specific incidence of BSE in France using a birth-cohort model with validated parameter estimates obtained from back-calculation analysis of the British BSE epidemic. Allowing for under-reporting, the results indicate that the risk of infection with the agent for BSE dropped dramatically from 1988 to 1991.
Dr Donnelly suggests that the subsequent rise in infection risk between 1991 and 1996 reflects the recycling of infectious material within the French feed industry. Although the inclusion of ruminant tissue from the central nervous system in French meat and bonemeal was banned in mid-1996, it is too soon to judge the effectiveness of this ban.
Dr Donnelly says: "I estimate that, since mid-1987, 7,300 French cattle were infected with BSE. This estimate is reduced to 1,200 if it is assumed that case reporting is complete; however, under-reporting is highly significant and the steady rise in BSE incidence from 1987 to 1996, estimated on the assumption of complete reporting, is difficult to explain."
She estimates that 100 infected animals will have been slaughtered for consumption during 2000 in France, with the slaughter of 52 of these estimated to have occurred within 12 months of the clinical onset of BSE. Assuming complete reporting, these estimates are reduced to 49 and 24 respectively. By comparison, the estimated number of infected animals slaughtered for consumption in 2000 in Great Britain within 12 months of clinical onset is 1.2.
She concludes: "These epidemiological analyses indicate that the relative potential risks posed by the consumption of British and French beef warrant re-examination."
Notes to editors:
1) Title: Likely magnitude of the French BSE epidemic. Author: Dr Christl Donnelly, Imperial College. Nature Vol 408 No 6814 pp787-788 (14 December 2000).
2) Dr Christl Donnelly, was appointed as Reader in Epidemiological Statistics at Imperial College in November 2000. She was formerly Head of the Statistics Unit at the Wellcome Trust Centre, Oxford University.
3) Imperial College established the new department of Infectious Disease Epidemiology in November 2000 within its Division of Primary Care and Population Health Sciences on the St Mary’s campus. The Department is headed by Professor Roy Anderson, FRS, Professor of Infectious Disease Epidemiology. He was formerly Director of the Wellcome Trust Centre for the Epidemiology of Infectious Disease at the University of Oxford. Professor Anderson is a world leader in the mathematical modelling of how infectious agents such as HIV and BSE spread.
This new department will undertake research into all aspects of infectious disease epidemiology. The department will foster interdisciplinary research in the study of infectious disease, using approaches ranging from molecular epidemiology, through field programmes of research, to mathematical studies of transmission dynamics and disease control.
The department has 32 staff, including 8 academic members. It is a UNAIDS collaborating centre for the epidemiology of HIV and AIDS, a WHO collaborating centre for intestinal infections and it houses the Partnership for Child Development which is funded by UNICEF and the World Bank. The staff of the department carry out research on a wide range of infectious diseases including HIV, influenza viruses, pneumococcal and meningococcal bacteria, BSE, vCJD, and a variety of parasitic infections. The department houses state of the art parallel processing computational facilities for large database analysis and mathematical model development, and high through put sequencing machines for the study of pathogen diversity. Web site at: http://www.med.ic.ac.uk/divisions/template_divisions_departments.asp?id=85
4) Imperial College of Science, Technology and Medicine is an independent constituent part of the University of London. Founded in 1907, the College teaches a full range of science, engineering, medical and management disciplines at the highest level. The College is the largest applied science and technology university institution in the UK, with one of the largest annual turnovers (£330 million in 1998-99) and research incomes (£173 million in 1998-99). Web site at http://www.ic.ac.uk
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