An integrated approach to assessing the viability of eradicating BVD in Scottish beef suckler herds

The viability of eradicating bovine viral diarrhoea (BVD) in Scottish suckler herds is dependent on the continued compliance with eradication schemes. At the farm level, the costs of BVD have been identified in previous studies and show a substantial financial imperative to avoid infection. At a regional level the incentives of BVD eradication to individuals are unclear, for example the requirement for vaccination strategies despite achieving disease-free status. Ensuring farmer compliance with an eradication scheme is therefore difficult. Experience of eradicating BVD from beef-dominated areas is limited and theoretical models have tended to focus on the dairy sector. Here we present a stochastic epidemiological model of a typical beef suckler herd to explore the interaction of a farm with a regional pool of replacements, utilising information from a BVD virus seroprevalence survey of Scottish beef suckler herds. Our epidemiological model is then used to assess the relative costs to individuals assuming different regional endemic prevalences, which are used to represent the likelihood of BVD re-introduction. We explore the relative cost of BVD, taken as likelihood and consequence, at an endemic steady state in contrast to previous models that have assumed the introduction or control of BVD in an epidemic state (e.g. a closed and mostly susceptible population). Where endemic, BVD is unlikely to affect all farms evenly and will cost most farmers very little due to herd immunity or self-clearance of the virus. Compliance is likely to be boosted by pump-priming to initiate and complete eradication schemes with cost-sharing.