title: Induced sero-conversion in heifers with a field strain of bovine pestivirus--a comparison of methods and doses.
abstract: Losses from pestivirus infection in a closed herd of cattle occurred over several years. In order to prevent further losses, controlled exposure of non-pregnant heifers to pestivirus from viraemic carrier animals was undertaken. Two initial experiments were conducted using either intra-nasal EDTA blood or field contact. Subsequently, other yearling heifers were inoculated with various dilutions of serum using subcutaneous, conjunctival and intra-nasal routes. Effective doses were determined. Neither inoculation nor contact infection produced any clinical illness. The highest dilutions of serum at which sero-conversion occurred were conjunctival, undiluted; intranasal, 10(-1) and subcutaneous 10(-5). With the subcutaneous route all heifers sero-converted at 10(-3). The results for the subcutaneous inoculations showed that the 50% infectious dose for cattle was not distinguishable from that determined in cell culture. Inoculation with a field strain of pestivirus in freeze-thawed serum has effectively and safely induced sero-conversion in heifers. Inoculation of all cattle at risk is considered necessary because no secondary transmission from inoculated heifers was observed.
authors.affiliation: New South Wales Agriculture and Fisheries, Agricultural Research Centre.
authors.forename: L G
authors.initials: LG
authors.lastname: Cook
authors.forename: I R
authors.initials: IR
authors.lastname: Littlejohns
authors.forename: T M
authors.initials: TM
authors.lastname: Jessep
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis; D002353:Carrier State / Q000097:blood / Q000276:immunology / Q000662:veterinary; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000517:prevention & control*; D005260:Female; D007114:Immunization; D010576:Pestivirus / Q000276:immunology*; D014036:Togaviridae Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D014766:Viremia / Q000276:immunology
chemical_list: D000914:Antibodies, Viral