Recommendations for the testing and control of bovine viral diarrhoea in New Zealand pastoral cattle production systems

Eradicating bovine viral diarrhoea (BVD) from cattle populations requires a clear approach for determining the epidemiological status of individual herds and implementing the appropriate control measures to ensure the transmission cycle is cost-effectively broken. This is particularly important in countries such as New Zealand where there is currently no coordinated national programme and the herd-level decisions to control BVD are left to the discretion of individual farmers and veterinarians. To ensure greater consistency in the information being delivered by different stakeholders, we review the epidemiology of BVD in the context of New Zealand pastoral production systems and provides a series of simplified recommendations for the future control of BVD in beef and dairy herds. Based on analysis of BVD test accession data from commercial diagnostic laboratories, it has been estimated that 40.6% of dairy herds and 45.6% of beef herds tested had positive results for antibodies to BVD virus. While BVD continues to remain widespread and under voluntary control in New Zealand, it is recommended that herds test all individual mixed-age cows and replacement heifers for BVD virus or antigen and remove persistently infected animals from the breeding population. All new breeding animals that have entered the herd either through purchase or birth should also be tested for BVD virus. Biosecurity risks should be managed by reducing contacts with other herds and implementing targeted vaccination programmes. All individual purchased cattle should be tested and confirmed negative for BVD virus before being moved onto the buyer's property, even if the herd of origin had a negative antibody-based screening test. Herds should continue annual antigen or virus testing of all calves as soon as possible after birth to identify any persistently infected animals.