The prevalence of bovine viral diarrhoea virus infection in beef suckler herds in Scotland.

Bovine viral diarrhoea (BVD) is an endemic disease of cattle that causes substantial losses to both beef and dairy production worldwide. The goal of this study was to estimate the prevalence of active BVD virus (BVDV) infection in beef suckler herds in Scotland. Information was collected from 301 herds using a stratified random sampling design based on agricultural census data. Herds were classified as with and without active infection based on the within-herd BVDV seroprevalence in young stock using Bayesian finite mixture modelling. This method accounted for within- and between-herd variability and allowed for classification error by the diagnostic tests. The observed sample data enabled the discrimination of three distinct seroprevalence cohorts. The results provided evidence of active BVDV infection in 16% of herds and no evidence of recent exposure in approximately two thirds of herds. The epidemiological significance of the further 16% of herds containing young stock with a median BVDV seroprevalence of 26.3-38.5% remains unclear. The fact that a large percentage of herds did not show evidence of recent infection is encouraging from an animal health and welfare perspective and the study provides a model for the further exploration of strategies aimed at BVD control at national level.