Oral and Poster Abstracts

Conclusion: It can be concluded that transmission of BVDV from PI
animals to naive in-contact animals occurred in a very efficacious and
fast manner, even if the animals are housed in adjacent pens. The
practical implications of these findings for BVDV control programs
will be discussed.
89 BVDV Type 1 and 2 Fetal Protection following the Use of a
Modified Live Viral Vaccine
W. Xue, D. Mattick, L. Smith, J. Maxwell
Intervet-Schering Plough, R&D Desoto, Desoto, United States
Objectives: Previously, it has been demonstrated that pre-breeding
vaccination with a modified live virus (MLV) vaccine (Vista R 5 SQ,
Intervet International) containing BVDV Type 1 and Type 2 strains,
offers protection against persistently infected fetuses when dams are
challenged with BVDV type 1 and type 2 in the first trimester. The
animal trials presented here were designed to demonstrate the efficacy
of the MLV vaccine in protecting fetuses from infection with BVDV
type 1 or type 2, when pregnant cows were challenged in the last
trimester, at 170 days of gestation.
Materials and Methods: Heifers, seronegative to BVDV, were
vaccinated at pre-breeding, and then bred naturally 4 weeks postvaccination.
Eighty-three pregnant heifers were challenged with
either type 1 (37 in total with 25 vaccinated and 12 controls), or type
2 (46 in total with 28 vaccinated and 18 controls) non-cytopathic
(ncp) BVDV field isolates at about 170 days of gestation. Fetuses
were collected from the challenged heifers 60 days post-challenge
(for type 2 BVDV challenge), and newborn calves were collected
prior to taking colostrum (for type 1 BVDV challenge). Serum
samples were taken from the fetuses or calves for a BVDV serum
neutralizing (SN) antibody test. Tissue samples of thymus, lung,
spleen and kidney were collected from the fetuses or calves, and
were used for virus isolation.
Results: Results of SN antibody tests revealed that 100% of fetuses
or calves from control heifers developed SN antibody to BVDV.
However, only 4 out of 22 calves born to vaccinated heifers were
positive for SN antibody in the type 1 BVDV challenge study, and 7
of 28 fetuses from vaccinated heifers were positive for the SN
antibody in the type 2 BVDV challenge study. Virus isolation from
calves’ tissue samples demonstrated the presence of type 1 BVDV in
5 of 12 calves from control heifers and none of the calves from
vaccinated heifers. The type 2 BVDV was isolated from 17 of 18
fetuses in the control group, and 2 of 28 fetuses in the vaccinate
group.
Conclusions: Results demonstrated that MLV vaccine Vista R 5 SQ
prevented fetal infection by at least 82% to type 1 BVDV, and 75% to
type 2 BVDV, when the dams were exposed to BVDV at about 170
days of gestation. Vaccine Vista R 5 SQ is the first MLV BVDV vaccine
that has proven to prevent fetal infection in the last trimester of
pregnancy.
90 Fetal Protection against Bovine Viral Diarrhea Virus Type 1
Infection Using One Shot of the Mucosiffa Modified-live Virus
Vaccine
G. Meyer 1 , M. Deplanche 2 , D. Roux 1 , M. Moulignie 2 ,
D. Raboisson 1 , N. Hagen-Picard 1 , P. Mathevet 3 , F. Schelcher 1
1
National Veterinary School of Toulouse, Pathology of Ruminants,
Toulouse, France
2
National Institure of Agronomical Research, Animal Health
Department, Toulouse, France
3
Merial Animal Health Limited, Lyon, France
Objective: To evaluate the efficacy of a commercially available live
Bovine Viral Diarrhea virus (BVDV) vaccine to protect against fetal
infection in pregnant cattle.
Method: Thirty beef heifers were allocated into 2 groups. One group
(18 heifers) was vaccinated against BVDV with one shot of a
commercially (Mucosiffa R , Merial) live vaccine according
manufacturer’s recommendations, and the other group (12 heifers)
served as nonvaccinated control cattle. The vaccine contained 10 3.5
TCID50 per vaccination dose (2.0 ml) of cp BVDV-1 Oregon C 24 V
strain. One month later, estrus was induced and the heifers were bred.
Three cycles of insemination were performed. Pregnancy was
confirmed by transrectal ultrasonographic examination and bovine
pregnancy-associated glycoprotein quantification. Four months after
78 XXV. Jubilee World Buiatrics Congress 2008
vaccination, 13 vaccinated and 9 non vaccinated pregnant heifers were
intranasally challenged with 10 6 TCID 50 of the BVDV-I 22146/Han
strain, on days 49-96 of gestation. Seroconversion, clinical signs,
mortality, abortion rate, hematology, viremia, and fetal infection were
studied.
Results: By ELISA or neutralization assay, all vaccinated animals
seroconverted to BVDV four weeks after immunization.
Neutralizing antibodies reached a plateau two month after
vaccination with titers ranging from 5970 to 14159 ED50/ml.
Challenge was followed by a rise of 0.57 log of neutralizing antibody
titer for vaccinated animals and by seroconversion for control
heifers. Post-challenge, all heifers were free from clinical signs of
BVD. Viremia was not detected by real time RT-PCR for 18 days
post-challenge in any of the vaccinated heifers. In contrast, 100% of
the control animals were BVDV viremic on at least one day between
days 4 to 18 post-challenge. Transient leucopenia with lymphopenia
was observed for heifers of the control group but not of the
vaccinated one. BVDV type 1 infection led to abortion only in one
unvaccinated heifer, 47 days after challenge and virus was detected
by real time RT-PCR in the spleen of aborted fetus. Three months
after challenge, all fetuses were harvested from heifers and tested for
evidence of BVDV infection. BVDV was detected with high viral
charges by qRT-PCR in the spleen, thymus, cerebellum and placenta
from 8 of 8 fetuses obtained from control heifers but from none of
the fetuses obtained from the 13 vaccinated heifers.
Conclusion: The commercial monovalent Mucosiffa R live vaccine is
safe and fully protective against fetal BVDV type 1 infection and
abortion.
Key words: bovine viral diarrhea, vaccination, fetal protection
91 Impact of Live and Killed Marker IBR Booster Vaccinations
on BoHV-1 Shedding after Primovaccination with Live
Marker IBR Vaccine
M. Pearce, I. Vangeel
Pfizer Animal Health, Sandwich, United Kingdom
For BoHV-1 control it is important to minimise virus shedding from
infected cattle. It has been suggested that killed vaccines are more
effective at suppressing BoHV-1 shedding than live vaccines. This
study compared the impact of live and killed marker IBR booster
vaccines on BoHV-1 shedding after challenge and reactivation
following primovaccination with live marker IBR vaccine. Twenty
BVDV free calves aged 12-14 weeks with no antibodies against
BoHV-1 and BVDV were given 2 doses of live IBR vaccine IM 3
weeks apart. Six months after primovaccination, 10 calves received
one IM dose of live IBR vaccine; the other 10 calves received one
dose of killed IBR vaccine. Live vaccine was Rispoval ® IBR marker
vivum; killed vaccine was Rispoval ® IBR marker inactivatum. Ten
control calves received saline IM at the time of each vaccination. Six
months after booster vaccination all cattle were challenged
intranasally with 10 8.0 TCID 50 BoHV-1, Iowa strain. Six weeks after
challenge, calves were given dexamethasone at 0.1 mg/kg
bodyweight IV daily for five days. Cattle were blood sampled
weekly for three weeks after booster vaccination and tested for
neutralising antibodies against BoHV-1. After challenge and
reactivation, nasopharyngeal swabs were taken daily for 21 days and
tested for the presence of BoHV-1 by virus isolation. Boosting with
inactivated vaccine gave higher titres of BoHV-1 neutralising
antibodies (P