Control of Bovine Viral Diarrhoea Virus

Any eradication program in a herd should start with the evaluation of the BVDV status. A serological survey of the herd should preferably be done separately for the milking herd, the pregnant heifers and the bulling heifers if these are housed seperately. The seronegative animals should then be tested for BVD viremia to identify PI animals. These need to be removed as soon as possible.

Diagnostics

Serology

The antibody testing can be done on milk and serum.

Bulk or pooled samples can be tested first prior to the testing of individual samples.

Virus testing

Antigen ELISA tests or PCR can be used for this purpose.

The so-called “ear notch” – biopsies that can be taken with specially designed ear tags can be used as substrate for PCR testing of newborn calves. 

Eradication plan

Based on the serological status of the herd, an eradication plan should be developed. In most cases, vaccination will be inevitable to stop the virus circulation in the herd.

During the first two years of a BVDV control program it is often advisable to continue the screening of the new-born calves for BVDV antigen. Once the situation has become stable, it is sufficient to monitor the animals in the 6-12 months age group for antibodies. These animals should be free of maternally derived antibodies and have not yet been vaccinated. If a PI calf is born in the herd this will become evident by seroconversion in this age group.

Inactivated BVD vaccines have been shown not to elicit antibodies against the NS3 which means that monitoring of virus circulation can be implemented also in vaccinated animals when the lab uses an ELISA test that measures antibodies against the NS3.

Vaccination

The major objective of BVDV vaccination is the prevention of foetal infection. Therefore, vaccination usually focuses on breeding animals.

Heifers should receive their basic vaccination prior to breeding and, thereafter, should be re-vaccinated at regular interval to assure solid immunity during the critical first phase of gestation. BVDV eradication in a herd usually takes a number of years. It is essential to continue vaccination until no new PI animals are born and to ensure that BVDV is not re-introduced into the herd from other sources.

The decision to stop vaccination in a herd must consider the risk for new infections. Once vaccination is stopped, the young heifers entering the breeding herd are fully susceptible for BVDV, therefore any new infection with the
virus will cause severe losses.

Dolorex

Steps in a BVDV eradication programme

  • Evaluate the BVDV status
    - Determination of the BVDV antibody level in the herd.
    - Identification of PI animals.
  • Removal of the PI animals
  • Herd vaccination programme
  • Monitor the herd for
    - Birth of new PI animals (minimum one year after the
    removal of the last PI)
    - Re-introduction of the virus from other sources.