Oral and Poster Abstracts

vaccine, mainly live vaccine. Due to the lack of combined vaccine
containing IBR marker, the use of IBR marker vaccine
simultaneously or concurrently with other vaccines is applied,
mainly in large dairy herds.During the period 2000-2007, the follow
up of the eradication has been performed in 232 dairy herds. The
herds applied vaccination with marker vaccines without culling of
seropositive animals and a mean replacement ratio of 30%. On the
whole 88 herds achieved the eradication. The mean time to reach the
eradication ranged from 3 years and 8 months to 6 years and 10
months depending from the herd size and the starting
seroprevalence. During the period of observation, in 32 (14%) of 232
herds we have detected seroconversion to gE but in only 1 case the
seroconversion was associated to clinical signs related to BoHV-1
infection.
246 Epidemiology and Eradication of the BHV1-Infection by the
Example of Selected Farms in Lower Saxony
J. Teuffert, K. Wiedl, F. Conraths
Friedrich-Loeffler-Instutute, Department of Epizootiology, Berlin,
Germany
Objectives of study: A case-control study was conducted over two
years (February 2004 - February 2006) in five selected administrative
districts (Landkreise) in Lower Saxony to determine potential risk
factors for the eradication of BHV1.
Materials and Methods: Fourty-two control farms (cattle negative for
BHV1) and 43 farms with an ongoing BHV1-eradication program
(positive for BHV1; case farms) were chosen and studied on the basis
of defined criteria. Information and data were collected regarding farm
management, the BHV1 control and, if applicable, the BHV1
immunisation strategy. Moreover, data on milk production and fertility
were analysed for individual animals as well as herds. For this purpose,
the BHV1 test protocols and vaccination lists that had been collected
from various farms by the local veterinary authorities were compared.
Finally, the farms were visited and the farmers interviewed using a
standard questionnaire.
Results: The statistical analysis revealed significant differences
between the farm categories for 19 of the operational and
management variables. In the evaluation of the data collected on
individual infected animals, the distribution of age classes at the
time of the first positive test result and the duration the infected
animals remained on the farms until slaughter proved to be
significantly different between case and control farms. In particular,
the analysis of the vaccination strategy showed that the following
factors differed between BHV1-negative and positive farms: the
number of animals with proper basic immunisation, the distribution
of the number of vaccinations administered in given intervals, the
proportion of infected but unvaccinated animals, and the time lapse
between the date of the first BHV1-positive test results and the
measures taken. The differences in milk production and fertility
between case and control farms, however, were not significantly
different. Also, no significant difference was found in the
performance of BHV1-positive and BHV1-negative cattle.
Conclusions: In summary, the results of this study lead to
recommendations on vaccination, care and feeding, transportation,
trade and documentation in cattle farms to improve BHV1 control.
Key words: BHV-1, epidemiology, risk factors, case control study
247 Evaluation of the Probability of Transmission of a Live
BoHV-1 Marker Vaccine to Sentinels after Intranasal or
Intramuscular Application
B. Makoschey 1 , J. Patel 2 , M. Beer 3
1
Intervet-Schering-Plough, Int. Marketing, Boxmeer, Netherlands
2
JAS Biologicals Ltd, Int. Marketing, Cambridge, United Kingdom
3
Friedrich-Loeffler-Institut, Institute of Diagnostic Virology, Insel
Riems, Germany
Objectives: Live marker vaccines against bovine herpesvirus type 1
(BoHV-1) infections are widely applied. The probability of
transmission vaccine virus to sentinels after intranasal or intramuscular
application should be determined.
Materials and Methods: Two studies have been performed to
investigate the transmission of a live BoHV-1marker vaccine (Bovilis ®
IBR marker live, Intervet) virus after combined intramuscular (IM) and
intranasal (IN) vaccination. A group of five (1 st study) or six (2 nd study)
BoHV-1 negative calves was vaccinated with a 10x overdose of the
vaccine IN and IM. The animals were housed together with 5 (1 st
study) or 3 (2 nd study) unvaccinated calves during 2 weeks. Nasal swab
samples were taken daily and tested for BoHV-1 vaccine virus. In a 3 rd
study, it was established, whether animals vaccinated IM with the same
vaccine become viremic and / or excrete vaccine virus with nasal
discharge. Five animals were vaccinated once with an overdose via the
IM route. Nasal swab samples were taken daily for 11 days. Blood
samples were taken three times a week during the first two weeks and
then once a week until four weeks after vaccination. The nasal swab
samples and the blood samples were tested for BoHV-1 in a virus
infectivity assay. In addition, a polymerase chain reaction (PCR)
specific for BoHV-1 DNA was performed on the blood samples.
BoHV-1 neutralising antibody titers were determined in the sera taken
prior to the vaccination and four weeks after immunisation.
Results: In the 1 st study, 1/5 in contact animals excreted a minimal
amount of vaccine virus during 1 day and developed a BoHV-1
antibody response at very low titer. All remaining sentinels in the 1 st
and 2 nd study did not excrete vaccine virus and remained seronegative.
In the 3 rd study, all animals were successfully vaccinated as judged by
the development of BoHV -1 neutralising antibodies. However, all
nasal swab samples were tested negative for vaccine virus, and all
blood samples were found negative for BoHV-1 virus and BoHV -1
specific DNA.
Conclusions: It can be concluded that transmission of the vaccine virus
to sentinels is very limited after intranasal vaccination and that no
vaccine virus was excreted with nasal discharge after IM vaccination,
nor could viremia of vaccine virus be detected. It is recommended to
apply the tested BoHV-1 marker live vaccine by the IM route in
situations where excretion of vaccine virus is undesirable.
248 Evolution of the Net Reproductive Ratio of Bovine Herpes
Virus Type 1 Infection in Hyperimmunized Dairy Herds: a
Longitudinal Study in the Field
M. Dispas 1 , R. Soares Magalhaes 2 , M. Pearce 3 , A. Dupont 1 ,
E. Thiry 4 , P. Kerkhofs 1
1
Veterinary & Agrochemical Research Centre, Virology, Brussels,
Belgium
2
Royal Veterinary College, Epidemiology, London, United Kingdom
3
Pfizer Animal Health, R&D, Sandwich, United Kingdom
4
Faculty of Veterinary Medecine-University of Liege, Virology,
Liege, Belgium
BoHV-1 control programmes have existed in Europe for 10 years.
When seroprevalence is high, hyperimmunization of cattle is usually
recommended to maximise virological protection. Marker vaccine
usage has been promoted to allow discrimination of vaccinated cattle
from cattle infected by a wild virus. Experimental studies show that
effective immunity can be obtained by administration of live then
inactivated vaccines (P1) but use of this protocol has in the field has
not been reported. A 28-month longitudinal field study was
conducted to compare the efficacy of protocol P1 with sole use of
inactivated vaccine (P2), and the usual vaccination protocol defined
as non intervention group (NIG). The study comprised 6 crosssectional
serosurveys of all cattle on farms enrolled in P1 (n=10), P2
(n=10) and NIG (n=16). New BoHV-1 infections were defined as gE
seroconversion. Vaccinations and blood sampling followed the same
schedule, providing 5 chronologically sequential time blocks: from
winter 1, summer 1 and so on to winter 3. Mean net reproductive
ratio (R) was calculated for each farm over the whole study and
within each time block to quantify transmission of BoHV-1 in partly
susceptible populations. Two methods were used: martingale
estimation (R mart) and a linear mixed model using a log link and
Poisson error distribution (R glm). Nine farms in P1, 8 in P2 and 13 in
the NIG contributed to the calculation of R values. The mean R marts
were, respectively, estimated to be 0.49, 0.61 and 0.70. Only the
R marts for P1 and P2 did not include the value 1 in their confidence
interval. In these groups BoHV-1 infection would fade out, but
would persist in NIG. Mean R glms were smaller when infectiousness
was presumed to be 3 days (respectively 0.23; 0.22 and 0.28 for P1,
P2 and NIG) compared with 7 days (0.55; 0 .52 and 0.64) or 10 days
(0.78; 0.74 and 0.92). In each group and respectively for the 5 time
blocks, within each group, seasonal changes were observed: P1,
0.64; 0.00; 0.37; 1.06 and 0.53; P2, 0.70; 0.77; 0.34; 0.73 and 0.41;
NIG, 0.70; 0.61; 0.88; 0.49 and 0.93. Only P1 and P2 showed R mart
values significantly smaller than 1, but not consistently. These
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