Evolution of the BSE epidemic in Catalonia (1990-2015) based on a stochastic model.

A stochastic model was used to estimate the number of bovine spongiform encephalopathy (BSE) cases that may have occurred in Catalonia (north-east Spain) from January 1990 to December 2015. The model allowed the evolution of the unobserved cases to be estimated differentiating the population into two subgroups: (1) livestock slaughtered for human consumption without clinical signs and (2) cattle at increased risk (including fallen stock, clinical suspects, emergency slaughtered cattle and cattle with clinical signs at ante mortem inspection). If the first bovine affected by BSE had been introduced into the region in 1986, the model predicted that during the period of study the surveillance system would detect a median of 197 outbreaks (2.5-97.5 percentiles: 157-245). The estimated median number of outbreaks that may have appeared before the establishment of the monitoring program was 80 (2.5-97.5 percentiles: 35-152), and the number of cases would have peaked in 2001.