International Journal of Epidemiology, Vol 28, 526-531, Copyright © 1999 by International Epidemiological Association
CH Cohen and AJ Valleron
BACKGROUND: Knowing the starting date of the BSE epidemic and its size at
the very beginning is crucial to interpret the timing of the nvCJD cases
and to forecast the nvCJD epidemic. The first cases occurred in 1985. The
models devised by Anderson (back-calculation) and Dealler
(age-period-cohort) led to an estimate of less than 50 cases in 1983, and
none earlier. Here, we applied age-cohort models to the BSE data in order
to estimate the earliest possible date of the first unrecognized BSE cases.
METHODS: The numbers of confirmed BSE cases in the UK, by age group and by
calendar year from 1988 to 1996, were analysed by Poisson regression. The
cases' age distribution was considered as constant between the different
birth cohorts. The herd's age structure was taken into account. RESULTS:
According to the models, BSE cases may have occurred as early as 1980. The
expected number of cases before 1990 is almost twice the number of
confirmed cases and exceeds by more than 20% the expected value of
Anderson's model. The scenario of first human exposure in 1980 leads to
fewer future nvCJD cases than predicted by Cousens with exposure patterns
starting in 1983 or 1985. CONCLUSION: The first birth cohort available,
consisting of two cases older than 10 in 1988, does not allow any
projections before 1980. Moreover, confidence intervals are wide and the
power of the study is limited by the great dispersion of the data; the
precision of the estimations would be improved by considering geographical
incidence. Nevertheless, our projections are consistent with Wilesmith's
survey of rendering plants relating the emergence of BSE to the dramatic
fall in the proportion of meat and bone meal following solvent extraction,
initiated in the late 1970s (65% in 1977 to 10% in 1983).
ARTICLES
When did bovine spongiform encephalopathy (BSE) start? Implications on the prediction of a new variant of Creutzfeldt-Jakob disease (nvCJD) epidemic
INSERM-Unite 444 Epidemiologie et Sciences de l'Information, Institut federatif Saint-Antoine de Recherches sur la Sante, faculte de Medecine Saint-Antoine, Paris, France.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  E. D. Belay, R. A. Maddox, P. Gambetti, and L. B. Schonberger Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in the United States Neurology, January 28, 2003; 60(2): 176 - 181. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.A. Critchley and S. Capewell Why model coronary heart disease? Eur. Heart J., January 2, 2002; 23(2): 110 - 116. [Full Text] [PDF]
|
|
|
|
 |
|
 A.-J. Valleron, P.-Y. Boelle, R. Will, and J.-Y. Cesbron Estimation of Epidemic Size and Incubation Time Based on Age Characteristics of vCJD in the United Kingdom Science, November 23, 2001; 294(5547): 1726 - 1728. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. H. Cohen Does Improvement in Case Ascertainment Explain the Increase in Sporadic Creutzfeldt-Jakob Disease Since 1970 in the United Kingdom? Am. J. Epidemiol., September 1, 2000; 152(5): 474 - 479. [Abstract] [Full Text] [PDF]
|
|