Search Results

Abstract

Objective—To determine the ability of a modified-live virus (MLV) bovine viral diarrhea virus (BVDV) type 1 (BVDV1) vaccine administered to heifers prior to breeding to stimulate protective immunity that would block transmission of virulent heterologous BVDV during gestation, thus preventing persistent infection of a fetus.

Animals—40 crossbred Angus heifers that were 15 to 18 months old and seronegative for BVDV and 36 calves born to those heifers.

Procedure—Heifers were randomly assigned to control (n = 13) or vaccinated (27) groups. The control group was administered a multivalent vaccine wherein the BVDV component had been omitted. The vaccinated heifers were administered a single dose of vaccine (IM or SC) containing MLV BVDV1 (WRL strain). All vaccinated and control heifers were maintained in pastures and exposed to BVDV-negative bulls 21 days later. Thirty-five heifers were confirmed pregnant and were challenge exposed at 55 to 100 days of gestation by IV administration of virulent BVDV1 (7443 strain).

Results—All control heifers were viremic following challenge exposure, and calves born to control heifers were persistently infected with BVDV. Viremia was not detected in the vaccinated heifers, and 92% of calves born to vaccinated heifers were not persistently infected with BVDV.

Conclusions and Clinical Relevance—These results document that vaccination with BVDV1 strain WRL protects fetuses from infection with heterologous virulent BVDV1. (Am J Vet Res 2003;64:530–537)

Abstract

Objective—To evaluate protection resulting from use of a modified-live noncytopathic bovine viral diarrhea virus (BVDV) type 1 vaccine against systemic infection and clinical disease in calves challenged with type 2 BVDV.

Animals—10 calves, 5 to 7 months of age.

Procedures—Calves were allocated (n = 5/group) to be nonvaccinated or vaccinated SC on day 0 with BVDV 1 (WRL strain). Calves in both groups were challenged intranasally with BVDV type 2 isolate 890 on day 21. Rectal temperatures and clinical signs of disease were recorded daily, and total and differential WBC and platelet counts were performed. Histologic examinations and immunohistochemical analyses to detect lesions and distribution of viral antigens, respectively, were performed.

Results—After challenge exposure to BVDV type 2, nonvaccinated calves developed high rectal temperatures, increased respiratory rates, viremia, leukopenia, lymphopenia, and infection of the thymus. Vaccinated calves did not develop high rectal temperatures or clinical signs of respiratory tract disease. Vaccinated calves appeared to be protected against systemic replication of virus in that they did not develop leukopenia, lymphopenia, viremia, or infection of target organs, and infectious virus was not detected in peripheral blood mononuclear cells or the thymus.

Conclusions and Clinical Relevance—The modified-live BVDV type 1 vaccine protected against systemic infection and disease after experimental challenge exposure with BVDV type 2. The vaccine protected calves against infection and viremia and prevented infection of target lymphoid cells.

Abstract

Objective—To determine whether maternally derived antibodies interfere with the mucosal immune response following intranasal (IN) vaccination of newborn calves with a multivalent modified-live virus vaccine.

Design—Randomized controlled clinical trial.

Animals—23 newborn Holstein bull calves.

Procedures—Calves received colostrum and were assigned to group A (unvaccinated control calves), group B (IN vaccination on day 0), or group C (IN vaccination on days 0 and 35). Serum and nasal secretion sample (NSS) titers of antibodies specific for bovine herpesvirus 1, bovine viral diarrhea virus 1, and bovine viral diarrhea virus 2; WBC counts; and NSS interferon concentrations were determined up to day 77.

Results—Calves had high serum titers of maternally derived antibodies specific for vaccine virus antigens on day 0. High IgA and low IgG titers were detected in NSSs on day 0; NSS titers of IgA decreased by day 5. Group B and C NSS IgA titers were significantly higher than those of group A on days 10 through 35; group C IgA titers increased after the second vaccination. Serum antibody titers decreased at a similar rate among groups of calves. Interferons were not detected in NSSs, and calves did not develop leukopenia.

Conclusions and Clinical Relevance—IN vaccination of newborn calves with high concentrations of virus-neutralizing antibodies increased NSS IgA titers but did not change serum antibody titers. Revaccination of group C calves on day 35 induced IgA production. Intranasal vaccination with a modified-live virus vaccine was effective in calves that had maternally derived antibodies.

Abstract

Objective—To evaluate protection against systemic infection and clinical disease provided by use of a modified-live noncytopathic bovine viral diarrhea virus (BVDV) type 1 vaccine in calves challenged with NY-1 BVDV.

Animals—10 calves, 5 to 7 months of age.

Procedures—Calves were allocated (n = 5/group) to be nonvaccinated or vaccinated SC on day 0 with BVDV type 1 (WRL strain). Calves in both groups were challenged intranasally with NY-1 BVDV on day 21. Calves' rectal temperatures and clinical signs of disease were recorded daily, total and differential WBC and platelet counts were performed, and serum neutralizing antibody titers against NY-1 BVDV were determined. Histologic examinations and immunohistochemical analyses to detect gross lesions and distribution of viral antigens, respectively, were performed.

Results—After challenge exposure to NY-1 BVDV, nonvaccinated calves developed high rectal temperatures, increased respiratory rates, viremia, leukopenia, lymphopenia, and infection of the thymus. Vaccinated calves did not develop high rectal temperatures or clinical signs of respiratory tract disease. Vaccinated calves appeared to be protected against systemic replication of virus in that they did not develop leukopenia, lymphopenia, viremia, or infection of target organs, and infectious virus was not detected in peripheral blood mononuclear cells or the thymus.

Conclusions and Clinical Relevance—The modifiedlive BVDV vaccine protected calves against systemic infection and disease after experimental challenge exposure with NY-1 BVDV. The vaccine protected calves against infection and viremia and prevented infection of target lymphoid cells. (Am J Vet Res 2005;66:1785–1791)

Abstract

Objective—To assess the serologic response of calves to inactivated and modified-live (ML) Mannheimia haemolytica (MH) preparations given alone and concurrently with combination viral vaccines containing ML bovine herpesvirus type 1 (BHV-1).

Animals—642 calves seronegative for BHV-1.

Procedures—In experiment 1, 192 calves received 1 of 3 MH preparations alone or concurrently received 1 of 3 MH preparations and 1 of 4 combination viral vaccines. In experiment 2, 450 calves received 1 of 4 MH preparations alone or concurrently received 1 of 4 MH preparations and 1 of 5 combination viral vaccines. Pretreatment and posttreatment blood samples were processed to obtain serum, which was analyzed to detect concentrations of antibodies against MH leukotoxin and BHV-1.

Results—In experiment 1, antibody titers against MH leukotoxin in calves receiving MH and ML virus vaccine appeared decreased, albeit nonsignificantly, compared with titers for calves receiving MH preparations alone. In experiment 2, all groups (except for 1) concurrently receiving an MH preparation and viral vaccine had a significant decrease in antibodies against MH leukotoxin. In both experiments, there was a significant decrease in the number of calves responding to MH leukotoxin when ML viral vaccine was coadministered.

Conclusions and Clinical Relevance—Coadministration of ML BHV-1 and MH preparations interfered with the serologic response to MH leukotoxin in calves seronegative for BHV-1. Serologic response to MH leukotoxin may be substantially improved in seronegative calves when MH vaccination is delayed until after calves have received a dose of ML BHV-1 vaccine.