Modelling the effects of previous infection and re-infection on the costs of bovine viral diarrhoea outbreaks in beef herds

A previously published model was re-employed to examine the potential impact of different epidemiological circumstances on output losses due to bovine viral diarrhoea virus (BVDV) infection in typical British hill cow-calf enterprises. The average annuity equivalent of unchecked losses from 100 simulated 10 year disease scenarios ranged from almost £0/cow to approximately £40/cow. Significant differences were found under certain circumstances, depending on the initial disease status of the herd, the initial source of virus, the probability and source of further infection, the probability of virus transmission within the herd and herd size. For naïve herds, losses depended only on the risk of incursion. In most other circumstances, the losses could be mitigated if the annual risk of incursion was <0.3 and risk of within herd transmission was extremely low. Greater understanding of the interaction between these risk factors and management actions are required so that total costs of BVDV infection can be minimised under different circumstances.