Modified-live bovine viral diarrhea virus (BVDV) type 1a vaccine provides protection against fetal infection after challenge with either type 1b or type 2 BVDV

Abstract

The objective of the study was to determine the efficacy of modified-live virus (MLV) BVDV type la (BVDV1a) vaccine against BVDV type 2 (BVDV2) or type 1b (BVDV1b) virus in fetal calves. The experimental vaccine administered to the cows and heifers had a minimum antigen load dose of MLV BVDV1a and a full (commonly marketed) antigen dose of infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI3), bovine respiratory syncytial virus (BRSV), and Leptospira serovars canicola, grippotyphosa, hardjo, icterohaemorrhagiae and 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 ?150 days of gestation (range 148-174 days), and the 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, and out of the 24 fetuses, 23 were negative and one fetus was positive for BVDV. These results suggest that vaccination with MLV BVDV1a vaccine significantly reduce fetal infection following challenge with BVDV2.