Oral and Poster Abstracts

3 Canadian Food Inspection Agency, Epidemiology and Surveillance
Section, Ottawa, Canada
Bovine Spongiform Encephalopathy (BSE) was first diagnosed in
Canada in 1993, in a cow imported from the United Kingdom. In 2003,
the first indigenous case of BSE was diagnosed. To the end of 2007, a
total of 12 indigenous cases of BSE had been diagnosed in cattle born
in Western Canada. From the time Canada made BSE reportable in
1990, surveillance has evolved from passive to active, with a markedly
greater intensity following the discovery of the first indigenous case.
To assess Canada’s true prevalence of BSE and the effectiveness of its
surveillance, a retrospective study was designed based on the random
selection of 3,712 samples from the 95,383 cattle brain samples
submitted for BSE testing between 1992 and 2005. The sampling plan
was based on an a priori estimation of the proportional distribution of
National, Western and Eastern BSE surveillance samples by Office
International des Epizooties (OIE) surveillance stream (clinical
suspect, casualty slaughter, fallen stock, and routine slaughter). For
each sample, data was obtained by record tracing and interviewing of
identifiable current and original owners. Information recorded
comprised sampling site and date, age of the animal, date of birth,
breed, production type, province of sampling, province of birth, clinical
signs preceding and reason for death, diagnostic test used and test
result. Each sample was classified by OIE surveillance stream.
Analyses on a National, Western and Eastern basis highlighted regional
variability among surveillance strategies. Reflecting underlying
population demographics and market flows, Eastern Canadian
surveillance emphasized deadstock/renderer sampling (70.5%) while
surveillance in Western Canada focused on on-farm sampling (84.1%).
Sampling in Western Canada was predominantly from beef cattle
(78.3%), with a mean age at sampling of 8.1 years. In Eastern Canada,
the majority of samples originated from dairy cattle (84%), with a mean
age at sampling of 4.7 years. The majority of samples examined were
classified as casualty slaughter (63.7% in Eastern Canada and 80.4% in
Western Canada). National, Eastern Canada and Western Canada
prevalence estimates were determined. Results of the study have
contributed to a broader assessment of the natural history of BSE in
North America.
86 Pregsure Trivalent Induces Much Higher Neutralising
Antibody Titres against BVDV-2 Strains than Monovalent
BVD Vaccines
R. Raue, D. Hurst, J. Salt
Pfizer Animal Health, R&D, Sandwich, United Kingdom
Objectives: Bovine viral diarrhoea virus (BVDV) is one of the most
common and economically important viruses causing infections in
cattle. Recently, severe outbreaks of BVDV-2 have been described in
the UK. In addition, isolation of BVDV-2 has been reported in most
European countries. As vaccination against BVDV is most often
performed with inactivated vaccines, neutralising antibodies can be a
good in vitro indicator of the ability to protect against a certain BVDV
strain or type. This study was designed to compare the neutralisation
antibody titres induced after vaccination with a novel vaccine PregSure
Trivalent (Pfizer Animal Health), Bovilis BVD (Intervet) and Bovidec
(Novartis Animal Health) against a panel of BVDV-1 and 2 strains.
Materials and Method: Serum samples were collected from calves 3
weeks after vaccination either with PregSure Trivalent, Bovilis BVD or
Bovidec according to the recommendations of the manufacturer. They
were tested in a serum neutralisation test against 11 BVDV-1 strains,
representing genotypes 1a, 1b and 1d to 1i, as well as 4 BVDV-2 strains
from Europe and the US.
Results: The geometric mean titre in log2 for the 11 BVDV-1 strains
were between 7.3 and 10.8 for PregSure Trivalent, 5.7 and 9.5 for
Bovilis BVD and 4.0 and 8.2 for Bovidec. With all vaccine sera
BVDV-1h strain G-AU was neutralised best and BVDV-1d strain
PI810 worst. The geometric mean titre in log2 for the 4 BVDV-2
strains where between 8.5 and 10.1 for PregSure Trivalent, 1.9 and 5.1
for Bovilis BVD and 1.2 and 2.2 for Bovidec. Therefore, PregSure
Trivalent serum samples showed an equal ability to neutralise BVDV-
1 and 2 strains whereas Bovilis BVD and Bovidec serum samples
showed a reduction in the ability to neutralise BVDV-2 strains by at
least 4 log2. In some cases Bovilis BVD and Bovidec vaccine sera were
not able to neutralise BVDV-2 strains at all.
Conclusions: The results of this study demonstrate that the level of
neutralising antibodies after vaccination with PregSure Trivalent is
remarkably higher against BVDV-2 strains than those of monovalent
inactivated BVD vaccines. In combination with the demonstration of
12 month protection against BVDV-1 and 2 by challenge, this data
indicate that the novel vaccine PregSure Trivalent gives a
comprehensive cover against all types of BVDV field infections.
Key words: PregSure Trivalent, BVDV-1, BVDV-2, neutralisation
87 Monitoring of a BVDV Infection in a Vaccinated Herd by
Testing of Milk for Antibodies against NS3
B. Makoschey 1 , H. Kuijk 2 , J. Mars 3 , W. bij de Weg 2 , P. Franken 3
1
Intervet-Schering Plough, Int. Marketing, Boxmeer, Netherlands
2
Intervet-Schering Plough, Intervet Netherlands, Boxmeer,
Netherlands
3
Animal Health Service Deventer, Deventer, Netherlands
Objectives: It has been demonstrated earlier, that an inactivated
vaccine against the bovine viral diarrhoea virus (BVDV) in
combination with a suitable test for antibodies against non structural
proteins (NS) exhibits properties of a marker vaccine: animals usually
remain seronegative after vaccination but develop NS specific
antibodies after field virus infection. In this study, it should be
established, whether the NS3 antibody testing of individual or bulk
milk samples is likewise suitable for differentiation between BVDV
vaccinated and field virus infected animals.
Materials and Methods: The study was performed on a Dutch dairy
farm. After being certified as BVDV-virus-free in 2002, the farm
experienced a new outbreak of BVDV in 2005. A herd vaccination
program was initiated using an inactivated BVDV vaccine (Bovilis R
BVD, Intervet International). Seventeen cows were selected for further
follow up: blood samples, individual milk samples and bulk milk
samples were collected at pre-set time points. BVDV neutralizing
antibody titers were measured and the NS3 antibody response was
measured in a commercial ELISA test (Cedi-testR BVDV, Cedi
Diagnostics, Lelystad, The Netherlands).
Results: All animals that were seronegative before vaccination
developed BVDV neutralizing antibodies after immunization. Three of
the ten vaccinated animals showed an increase in the titers of BVDV
neutralising antibodies, between study days 56 and 210, indicating that
they experienced a field virus infection. All samples from animals that
were vaccinated but not infected were tested negative for NS3 specific
antibodies at all time points. The samples from the three animals that
were infected after the vaccination were tested negative for NS3
specific antibodies at Day 0, 28 and 56, but were positive thereafter. In
contrast, all serum samples taken from animals that have been infected
with BVDV field virus were tested positive for NS3 specific antibodies.
The overall majority (37/44) of the milk samples for these animals were
also tested positive in the NS3 ELISA. Likewise, the bulk milk samples
were positive in the NS3 ELISA, with the exception of the sample
taken at study day 28.
Conclusions: The results obtained demonstrate that a field virus
infection with BVDV can be monitored by measurement of NS
antibodies in blood or (bulk) milk samples, even in a vaccinated herd.
88 Transmission of Bovine Viral Diarrhoea Virus (BVDV) from
Persistently Infected Calves to Naive in-contact Cattle is Very
Rapid and Efficient
B. Makoschey 1 , M. Janssen 2
1 Intervet-Schering-Plough, Int. Marketing, Boxmeer, Netherlands
2 Intervet-Schering Plough, R&D, Boxmeer, Netherlands
Objectives: The transmission of bovine viral diarrhoea virus (BVDV)
from persistently infected (PI) calves to in-contact animals is generally
considered to happen very efficiently. It should be determined, whether
naive animals housed in adjacent pens to a PI are readily infected or
whether housing in the same pen is required for efficient infection.
Materials and Methods: Four heifers at the age of 10 months or older,
negative for antibodies against BVDV, and free of BVDV and one three
months old PI calf were included in the study. The heifers were housed as
one group in a pen. The PI calf was housed in an adjacent pen. The animals
were allowed to have direct contact through the fence. Blood samples were
taken weekly and BVDV neutralising antibodies were determined.
Results: All four heifers seroconverted within four weeks after
introduction of the PI calf. These results, indicate that the infection with
BVDV had occurred during the first week after the first contacts with
the PI animal.
Infectious and Zoonotic Deseases (Public Health) 77