Submitted to: American Journal of Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/26/2010
Publication Date: 3/20/2011
Citation: Leyh, R.D., Fulton, R.W., Stegner, J.E., Goodyear, M., Witte, S., Taylor, L.P., Johnson, B.J., Step, D.L., Ridpath, J.F., Holland, B.P. 2011. Fetal protection in heifers vaccinated with a modified-live virus vaccine containing bovine viral diarrhea virus subtypes 1a and 2a and exposed during gestation to cattle persistently infected with bovine viral diarrhea virus subtype 1b. American Journal of Veterinary Research. 72(3):367-375. Interpretive Summary: Losses associated with fetal infection with bovine viral diarrhea viruses (BVDV) are significant for dairy and beef producers. In addition to the outright loss of fetuses due to abortion, surviving fetuses may be born with defects, not the least of which are life long persistent infections with BVDV. These persistently infected (PI) animals are a major source of BVDV infection in cattle herds. One goal of vaccination is the prevention of fetal infections. Typically the effectiveness of BVDV vaccines is determined by exposing animals to a one-time dose of virus. This does not reflect what happens in the field where infection is usually the result of being housed with a PI, which is constantly shedding virus. It was shown in this study that vaccination reduced fetal infection even when the source of infection was a PI.
Technical Abstract: The purpose of this study was to determine efficacy of a modified live virus (MLV) vaccine containing bovine viral diarrhea virus subtype 1a (BVDV1a) and subtype 2a (BVDV2a) in preventing fetal infection. To this end, seronegative and PI negative heifers were vaccinated by either the SC (10 heifers) or IM route (10 heifers) with vaccine containing MLV strains BVDV1a and BVDV2a or a placebo vaccine (8 heifers). Three weeks post vaccination (70-weeks gestation), heifers were challenged via exposure to cattle persistently infected (PI) with subtype BVDV 1b. Three weeks post-challenge fetuses were harvested and tested for the presence of BVDV by antigen capture ELISA (ACE) and virus isolation. All fetuses from placebo vaccinated heifers were positive for BVDV. In the MLV vaccinated groups, 3/20 (1 IM, 2 SC) of animals were positive for BVDV. This study demonstrated that administration of one dose of MLV vaccine containing BVDV1a and BVDV2a prior to breeding provides protection against fetal infection after the heifers were challenged by exposure to BVDV 1b PI cattle.