PROBABILITY OF DETECTING ANTIBODIES TO BOVINE HERPESVIRUS-1 IN BULK MILK AFTER THE INTRODUCTION OF A POSITIVE ANIMAL ON TO A NEGATIVE FARM

The purpose of this study was to assess the probability that the intro duction of one or more bovine herpesvirus 1 (BHV-1)-seropositive anima ls would result in the bulk milk of a clean herd becoming BHV-1-positi ve. Probability calculations (stochastic and deterministic) were based on the distribution of the log(titre) of 828 positive animals and the daily milk production of the herds and of the individual cows. They s howed that the probability in average sized herds of 45 dairy cows is only between 10 and 25 per cent and that even in small herds of 25 cow s the introduction of a positive animal would go undetected in the maj ority of cases. It is concluded that if the bulk milk has become BHV-1 -positive it is most likely that the infection has spread.