Quantifying BSE control by calculating the basic reproduction ratio R0 for the infection among cattle.

The safety of using meat and bone meal (MBM) in mammal feed was studied in view of BSE, by quantifying the risk of BSE transmission through different infection routes. This risk is embodied in the basic reproduction ratio R(0) of the infection, i.e. the average number of new infections induced by one initial infection. Only when R(0) is below 1, will the disease die out with certainty and the population will become free from BSE. Unfortunately this is a slow process due to the slow progression of the disease. We calculate R(0) explicitly from basic ingredients taking several different transmission routes into account. Several of the basic ingredients are functions of age or of infection-age. We also calculate the exponential growth rate r in terms of the same basic ingredients. Next we quantify the ingredients from available data and compute the effects on R(0) of various scenario's for controlling BSE, with examples for the UK and the Netherlands.