The voluntary phase of the BVD eradication programme is now well underway.

While the primary focus during the first three years of the programme is on tissue tag testing of calves to identify and address herds containing persistently infected (PI) cattle, the importance of adequate biosecurity to prevent the introduction or reintroduction of infection should not be overlooked.

By far the most common way for BVD virus to be introduced is through the purchase of PI animals. All new stock should be tested to confirm that they are not PI. Ideally this should be done pre-purchase, but where this is not possible animals should be isolated on arrival, particularly from contact with pregnant stock, and tested for BVD virus. As the programme develops, the proportion of cattle traded with pre-purchase negative test results is expected to steadily increase.

Although a much lesser risk, animals that have been tested pre-purchase and shown to be non-PI may also introduce infection, if they have acquired a transient infection around the time of purchase. Where this cannot be ruled out, it is recommended that animals are isolated from the rest of the herd for three or four weeks, again with particular emphasis on avoiding contact with pregnant stock.

International experience shows that the purchase of in-calf heifers and cows is a particular risk for the introduction of PI cattle, since a negative virus result only confirms the status of the mother but not of the calf she is carrying. Tag testing of calves born to purchased in-calf animals will address this problem but they should be isolated from other animals (particularly pregnant stock) until they have tested negative.

Apart from purchase, the next most important risk is contact with cattle from other herds, e.g. across boundaries, animals breaking in or out and at shows and sales. Visitors and the borrowing and sharing of contaminated equipment, ranging from nose tongs to trailers, present further risks for the introduction of infection.

It is recommended that each farmer, in consultation with their own veterinary practitioner, should put in place an adequate biosecurity plan to address these risks and prevent the introduction and spread of BVD virus and other infections. This will ensure that maximum benefit is obtained from the tag testing programme and that infection is not accidentally re-introduced.

For further information see www.bvdni.com or contact 028 8778 9126 (AHWNI) or your own veterinary practice