NR AXHT
AU Al-Zoughool,M.; Krewski,D.
TI Use of Back-Calculation Method to Estimate the Past Infection Rate of BSE and Predict the Future Course of vCJD
QU International Conference - Prion 2007 (26.-28.9.2007) Edinburgh International Conference Centre, Edinburgh, Scotland, UK - Book of Abstracts: Epidemiology, Risk Assessment and Transmission P04.30
IA http://www.prion2007.com/pdf/Prion Book of Abstracts.pdf
PT Konferenz-Poster
AB
Due to the long and variable incubation period of prion diseases including BSE and vCJD, current reported clinical cases do not necessarily reflect number of cases incubating the disease. In addition, there is great uncertainty in the future size of both BSE and vCJD because several epidemiological features of these diseases are still largely unknown. Therefore, it is critical to develop mathematical and simulation models to estimate retrospectively the number of animals infected with the etiologic agent and then estimate the extent of human exposure to infected cattle tissue.
The Back-calculation method was originally developed to obtain estimates of past HIVinfection numbers based on the incidence of AIDS cases, and to predict the future course of the disease. The method was successfully adapted for the analysis of BSE incidence data and it relies on the principle that the known number of clinical cases of BSE is due to an unknown number of animals infected in the past and the disease's incubation period. The method incorporates important parameters affecting the likelihood of infected cases eventually seen as clinical cases including probability of survival, time-dependent case reporting rate and age-dependent susceptibility/exposure of animals. The method can be also used to predict the future size of any vCJD in Humans.
The method has been used to estimate the rate of BSE infection in the UK, France and other European countries. The results showed significant underestimation of the epidemic in both France and the UK. In France, passive surveillance identified only 20% of infected case compared to complete case identification by the active surveillance system adopted in July 2001. Since Canada, USA and other countries still rely on the passive surveillance system and targeted screening for case reporting, it would be practical to apply this method to evaluate the extent of case underreporting, estimate the real incidence rate of BSE infection, provide estimates of the future scale of the epidemic, and assess the risk of vCJD.
AD M. Al-Zoughool, D. Krewski, McLaughlin Center for Population Health Risk Assessment, Canada
SP englisch
PO Schottland