Changes

A protocol for screening cattle herds for persistent infection should be implemented. Testing can be achieved by virus isolation or antigen-capture ELISA from serum or buffy coat cells, or by antigen detection in skin biopsies. The selected programme should be designed aroung the type and size of herd, financial limitations and the techniques available at the chosen diagnostic laboratory. Once identified, persistenly infected animals should be culled as soon as possible.

A protocol for screening cattle herds for persistent infection should be implemented. Testing can be achieved by virus isolation or antigen-capture ELISA from serum or buffy coat cells, or by antigen detection in skin biopsies. The selected programme should be designed aroung the type and size of herd, financial limitations and the techniques available at the chosen diagnostic laboratory. Once identified, persistenly infected animals should be culled as soon as possible.

Inactivated and modified live virus vaccines are available. They contain a variety of strains of BVDV representing both viral biotypes and viral genotypes 1 and 2. Antigenic diversity among BVDV may affect the efficacy of a given vaccine if the vaccine virus or viruses differ significantly from the challenge virus. Proper and safe immunization of cattle with either inactivated or modified live virus vaccines requires adherence to the manufacturer’s instructions. Because BVDV is fetotropic and may be immunosuppressive, use of modified live virus vaccines is not recommended in cattle that are pregnant or showing signs of disease. Inactivated viral vaccines may be used in pregnant cattle. Protection conferred by inactivated vaccines may be of short duration, and frequent vaccination may be necessary to prevent disease or reproductive failure. Colostral antibody confers partial to complete protection against disease in most calves for 3-6 mo after birth. Vaccination of neonatal cattle that have acquired colostral antibody may not stimulate a protective immune response, and revaccination at 5-9 mo of age may be necessary.

Both modified live and beta-propiolactone inactivated BVDV vaccines are available for used. Although cross-protection between strains and genotypes is generally good, antigenic diversity among challenge viruses may affect the efficacy of a given vaccine. Because BVDV is tropic for the foetus, and so modified live vaccines should not be used in pregnant animals. The virus is also immunosuppressive and so vaccination of animals showing signs of disease is not recommended. Maternally-derived antibody wanes at 3-6 months of age, and so to ensure that vaccination induces a protective immune response animals should be vaccinated (or re-vaccinated) after this age.

 

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