Objective—To evaluate onset of protection induced by modified-live virus (MLV) bovine viral diarrhea virus (BVDV) vaccine administered 7, 5, or 3 days before inoculation with type 1b BVDV (strain NY-1).
Procedures—Calves were assigned to 4 groups: an unvaccinated control group or groups vaccinated with MLV vaccine containing BVDV types 1a and 2 at 7, 5, or 3 days, before inoculation with NY-1 BVDV. Blood samples were collected for leukocyte counts, serum virus neutralization, and virus isolation (VI); nasal swab specimens (NSSs) were obtained for VI, and rectal temperatures were monitored for 14 days after inoculation.
Results—No significant differences in leukocyte counts or rectal temperatures were detected after BVDV inoculation in vaccinated calves. Vaccinated calves had reduced viremia and viral shedding after inoculation, compared with results for unvaccinated calves. On day 5 after inoculation, a higher proportion of calves vaccinated 3 days before inoculation had positive VI from NSSs, compared with NSS VI results for calves vaccinated 5 and 7 days before inoculation. Unvaccinated calves had leukopenia on days 3, 5, and 6 and had higher rectal temperatures on days 7 and 8 after inoculation, compared with temperatures before inoculation. All unvaccinated calves had ≥ 1 positive VI result from NSSs 3 to 11 days after inoculation, and 4 became viremic.
Conclusions and Clinical Relevance—MLV BVDV vaccine prevented fever, viremia, and leukopenia in calves challenge inoculated with NY-1 BVDV. A high proportion of calves vaccinated 3 days before inoculation shed BVDV after inoculation.
Objective—To evaluate persistence of bovine viral
diarrhea virus (BVDV) in semen after inoculation of
Animals—Three 2-year-old bulls and five 6-month-old
Procedure—3 seronegative 2-year-old bulls were
inoculated intranasally with BVDV. Serum and semen
samples were obtained at regular intervals until 7
months after inoculation. Serum samples were tested
for BVDV by use of virus isolation (VI) and reverse
transcription-nested polymerase chain reaction (RTnPCR)
tests. Semen samples were tested for virus by
use of VI and RT-nPCR tests. Testicular biopsy specimens
were obtained 7 months after inoculation and
tested for BVDV by use of immunohistochemical
analysis and VI and RT-nPCR tests. Semen samples
collected from 1 bull immediately before and 5 and 7
months after inoculation were administered IV to
seronegative calves, which were monitored for subsequent
viremia and seroconversion.
Results—Use of VI and RT-nPCR tests detected transient
virus in serum of all bulls. The VI test detected
BVDV in semen of 2 bulls for < 21 days after inoculation,
whereas RT-nPCR assay detected BVDV until 7
months after inoculation. Virus was detected in testicular
biopsy specimens of these 2 bulls by use of
immunohistochemical analysis and RT-nPCR assay
but could only be isolated from the biopsy specimen
of 1 bull. Of the calves administered semen IV to
detect infectious virus, only the recipient of semen
collected 5 months after inoculation of the adult bull
was viremic and seroconverted.
Conclusions and Clinical Relevance—Bovine viral
diarrhea virus can persist in semen of acutely infected
bulls for several months after exposure.
(Am J Vet Res 2003;64:428–434)
Objective—To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection.
Procedures—20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days.
Results—After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers.
Conclusions and Clinical Relevance—Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.