The objective of two bovine viral diarrhea virus (BVDV) fetal protection studies was to determine if vaccination with modified-live virus (MLV) BVDV type 1a (BVDV1a) vaccine would protect fetuses from infection with BVDV type 2 (BVDV2) or type 1b (BVDV1b) virus. The experimental vaccine administered to the cows and heifers had the minimum antigen load dose of MLV BVDV1a and the full (commonly marketed) antigen dose of infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI3), bovine respiratory syncytial virus (BRSV), and Leptospira Canicola-Grippotyphosa-Hardjo-Icterohaemorrhagiae-Pomona (Lepto-CGHIP) bacterin. In Trial A, 25 pregnant vaccinated cows and heifers and 10 pregnant unvaccinated controls were challenged with BVDV2. In Trial B, 25 pregnant vaccinated cows and heifers and eight pregnant unvaccinated controls were challenged with BVDV1b. In both trials, fetuses were obtained by Cesarean section, which was performed after approximately 150 days of gestation (range 148-174 days), and presence or absence of fetal BVDV infection was determined. All control fetuses were infected with BVDV. In Trial A, all fetuses (N = 25) of vaccinated dams were free of BVDV infection. In Trial B, one cow did not have a fetus at 150 days of gestation; of 24 fetuses, 23 were negative for BVDV and one fetus was positive for BVDV. In contrast to previous studies, these results suggest that vaccination with MLV BVDV1a vaccine will significantly reduce fetal infection following challenge with BVDV2.
Schnackel JA, Van Campen H, van Olphen A: Bov Pract 41(1):1-9, 2007