|Briggs, Robert - Bob|
Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract only
Publication Acceptance Date: 10/9/2003
Publication Date: 10/9/2003
Citation: FULTON, R.W., BRIGGS, R.E., RIDPATH, J.F., SALIKI, J.T., JOHNSON, B.J., CONFER, A.W., BRODERSEN, B.W., SMITH, D.R., STEP, D.L., SAWYER, J. PROTECTION BY PRIOR VACCINATION WITH MODIFIED LIVE VIRUS (MLV) BOVINE VIRAL DIARRHEA VACCINE AND SUBSEQUENT EXPOSURE TO PERSISTENTLY INFECTED CALVES. AMERICAN ASSOCIATION OF VETERINARY LABORATORY DIAGNOSTICIANS. 2003. ABSTRACT P. 147. Interpretive Summary:
Technical Abstract: The purpose of this study was to determine if calves vaccinated with a modified live virus (MLV) vaccine containing bovine viral diarrhea (BVDV) were protected against subsequent exposure to BVDV persistently infected (PI) calves. Eighty four calves were purchased on 9-17-02 and placed on pasture in Arkansas. Samples were collected for serology and nasal swabs/EDTA blood for peripheral blood leukocytes (PBL) to be tested for viruses. The calves were divided into two groups (42 each), vaccinates and nonvaccinates, with the vaccinates receiving a MLV vaccine containing BVDV, BHV-1, PI-3V, and BRSV on 9-17-02. One vaccinate died after a leg injury. On 10-12-02 the 83 calves were commingled with 18 purchased auction calves, and shipped to an experimental research feedyard. Upon arrival at Clayton, NM the calves were processed, 10-15-02 (day 0 of study) with samples for serology and viral isolation. The 41 vaccinates were revaccinated with the MLV vaccine. One nonvaccinate from 9-17-02 received the initial dose of MLV vaccine on 10-15-02. The 83 Arkansas calves plus the 18 salebarn calves were divided into six groups. Each pen contained 7 vaccinated and 7 nonvaccinated calves and 3 salebarn calves. The calves were negative for virus in both the nasal swabs and PBL collected on 9-17-02 and total transported calves on 10-15-02 (day 0). Four groups were placed in pens with 2 PI calves throughout the study ending on day 35. Two pens did not have PI calves. Two PI calves died on days 5 and 10. However the 2 fatal PI calves were in separate pens, and the remaining PI calves survived through day 35. Samples were collected for serology and viral isolation on days 7,14, and 35, and when the calves were febrile 104ºF and had respiratory disease signs. BVDV infections were detected by seroconversions between day 0 to 35 from calves exposed to PI calves in the same pen. In the 4 pens with the PI calves, 28/28 of the Arkansas nonvaccinates and 12/12 salebarn calves seroconverted to BVDV. Also BVDV was isolated from calves in these 4 pens: 14/28 nonvaccinates and 10/12 salebarn calves. Only one vaccinated calf had BVDV isolated which was from the nasal swab, but no PBL isolate. There was BVDV infection based on seroconversion and viral isolation from calves (2 pens) adjacent to the pens with PI calves. In these two pens there were 11/14 nonvaccinates seroconverting to BVDV. Thus, BVDV spread to adjacent pens without PI calves. Attempts were made to detect BVDV antigen using immunohistochemistry and antigen capture ELISA on ear notches. There were 51/60 calves undergoing acute BVDV infections based on seroconversions, with one additional calf BVDV viremic and seronegative on day 35. All 52 calves with acute BVDV infections were negative by both IHC and ELISA, and PI calves were positive by both tests on all collections. This study demonstrated that: (1) vaccination prior to exposure to BVDV reduced BVDV viremia; (2) for vaccine challenge studies exposure to PI calves represents a model relevant to natural exposure; and (3) skin test ELISA and IHC did not detect acute BVDV infections.