Two main diagnostic approaches are usually adopted within bovine viral diarrhoea (BVD) control programmes. One focuses on the identification of persistently infected (PI) animals with high levels of viremia for removal from the herd, This is done through direct diagnostic methods targeting the virus or antigen at animal level, as it has been applied to date within the Irish BVD eradication programme. The other focuses on surveillance at herd level, usually applying indirect diagnostic methods that target antibodies to the virus as transiently-infected animals that have been in contact with Pls will develop high levels of long-lasting antibodies.Since July 2022, the Irish BVD eradication programme has been officially approved by the EU Commission as a recognised programme under the new European Animal Health Law (AHL). This approval is a prerequisite for applying for recognition for freedom. When BVD freedom is achieved, it is envisaged that individual tissue tag testing of calves will be phased out and there will be a move toward serological surveillance which will assign a herd status based on serological testing of a subset of the herd, either by milk or serum, This surveillance is likely to lead to a lag in the time to the identification of any PI animals compared to the individual testing of all calves. The BVD Implementation Group is currently considering options for post-freedom surveillance to ensure prompt case detection in what is likely to be a phased approach.
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