Objective—To determine the effect of maternally
derived antibodies on induction of protective immune
responses against bovine viral diarrhea virus (BVDV)
type II in young calves vaccinated with a modified-live
bovine viral diarrhea virus (BVDV) type I vaccine.
Design—Blinded controlled challenge study.
Animals—24 neonatal Holstein and Holstein-cross
calves that were deprived of maternal colostrum and
fed pooled colostrum that contained a high concentration
of (n = 6) or no (18) antibodies to BVDV.
Procedure—At 10 to 14 days of age, 6 seropositive
and 6 seronegative calves were given a combination
vaccine containing modified-live BVDV type I. All
calves were kept in isolation for 4.5 months. Six
calves of the remaining 12 untreated calves were vaccinated
with the same combination vaccine at approximately
4 months of age. Three weeks later, all calves
were challenged intranasally with a virulent BVDV
Results—Seronegative unvaccinated calves and
seropositive calves that were vaccinated at 2 weeks
of age developed severe disease, and 4 calves in each
of these groups required euthanasia. Seronegative
calves that were vaccinated at 2 weeks or 4 months
of age developed only mild or no clinical signs of disease.
Conclusions and Clinical Relevance—Results indicate
that a single dose of a modified-live BVDV type-I
vaccine given at 10 to 14 days of age can protect susceptible
young calves from virulent BVDV type II infection
for at least 4 months, but high concentrations of
BVDV-specific maternally derived antibodies can block
the induction of the response. (J Am Vet Med Assoc
Objective—To determine whether single-fraction and combination modified-live bovine respiratory syncytial virus (BRSV) vaccines commercially licensed for parenteral administration could stimulate protective immunity in calves after intranasal administration.
Design—Randomized controlled trial.
Procedures—Calves were separated from dams at birth, fed colostrum with a minimal concentration of antibodies against BRSV, and maintained in isolation. In 2 preliminary experiments, 9-week-old calves received 1 (n = 3) or 2 (3) doses of a single-component, modified-live BRSV vaccine or no vaccine (8 control calves in each experiment), and were challenged with BRSV 21 days after vaccination. In a third experiment, 2-week-old calves received combination modifiedlive virus (MLV) vaccines with or without BRSV and calves were challenged with BRSV 8 days later. Calves were euthanized, and lung lesions were measured. Immune responses, including serum and nasal antibody and nasal interferon-α concentrations, were assessed.
Results—BRSV challenge induced signs of severe clinical respiratory tract disease, including death and pulmonary lesions in unvaccinated calves and in calves that received a combination viral vaccine without BRSV. Pulmonary lesions were significantly less severe in BRSV-challenged calves that received single or combination BRSV vaccines. The proportion of calves that shed virus and the peak virus titer was decreased, compared with control calves. Protection was associated with mucosal IgA antibody responses after challenge.
Conclusions and Clinical Relevance—Single and combination BRSV vaccines administered intranasally provided clinical protection and sparing of pulmonary tissue similar to that detected in response to parenteral delivery of combination MLV and inactivated BRSV vaccines previously assessed in the same challenge model.
Objective—To determine whether an inactivated
bovine respiratory syncytial virus (BRSV) vaccine
would protect calves from infection with virulent
Design—Randomized controlled trial.
Animals—27 nine-week-old calves seronegative for
Procedure—Group-1 calves (n = 9) were not vaccinated.
Group-2 calves (n = 9) were vaccinated on days
0 and 21 with an inactivated BRSV vaccine containing
a minimum immunizing dose of antigen. Group-3
calves (n = 9) were vaccinated on days 0 and 21 with
an inactivated BRSV vaccine containing an amount of
antigen similar to that in a commercial vaccine. All
calves were challenged with virulent BRSV on day 42.
Clinical signs and immune responses were monitored
for 8 days after challenge. Calves were euthanatized
on day 50, and lungs were examined for lesions.
Results—Vaccination elicited increases in BRSV-specific
IgG and virus neutralizing antibody titers and in
production of interferon-γ. Virus neutralizing antibody
titers were consistently less than IgG titers.
Challenge with BRSV resulted in severe respiratory
tract disease and extensive pulmonary lesions in control
calves, whereas vaccinated calves had less
severe signs of clinical disease and less extensive pulmonary
lesions. The percentage of vaccinated calves
that shed virus in nasal secretions was significantly
lower than the percentage of control calves that did,
and peak viral titer was lower for vaccinated than for
Conclusions and Clinical Relevance—Results suggest
that the inactivated BRSV vaccine provided clinical
protection from experimental infection with virulent
virus and decreased the severity of pulmonary
lesions. Efficacy was similar to that reported for modified-live BRSV vaccines. (J Am Vet Med Assoc 2001;218:1973–1980)
Objective—To characterize clinical signs and lesions
and identify the etiologic agent associated with epizootic
catarrhal enteritis in domestic ferrets.
Animals—119 ferrets with epizootic diarrhea of presumed
viral cause and 5 control ferrets.
Procedure—Clinical records and biopsy or necropsy
specimens of ferrets with presumed epizootic
catarrhal enteritis were reviewed. Immunohistochemical
staining for coronavirus antigen was performed
on paraffin-embedded tissues from approximately
10% of affected ferrets to identify viral antigen
and determine its distribution. Transmission electron
microscopy was performed on fecal samples and sections
of jejunum. Virus isolation studies as well as
immunofluorescent tests for other similar viruses
Results—Characteristic microscopic lesions consistent
with intestinal coronavirus infection (vacuolar
degeneration and necrosis of villus enterocytes; villus
atrophy, fusion, and blunting; and lymphocytic enteritis)
were consistently detected in affected ferrets.
Coronavirus particles were identified in feces and jejunal
enterocytes by use of transmission electron
microscopy. Immunohistochemical staining of jejunal
sections revealed coronavirus antigens. Antigen staining
was not detected in healthy ferrets or ferrets with
other gastrointestinal tract diseases. Virus isolation
was unsuccessful, and other similar viruses were not
Conclusions and Clinical Relevance—Results
strongly implicate a coronavirus as the causative
agent of epizootic catarrhal enteritis in ferrets.
Diagnosis may be made on the basis of a combination
of historical, clinical, and microscopic findings. (J Am
Vet Med Assoc 2000;217:526–530)
Objective—To compare isolates of Rhodococcus
equi on the basis of geographic source and virulence
status by use of pulsed-field gel electrophoresis
Sample Population—290 isolates of R equi(218 virulent
isolates from foals and 72 avirulent isolates from
feces, soil, and respiratory tract samples) obtained
between 1985 and 2000 from horses and horse farms
from 4 countries.
Procedure—DNA from isolates was digested with
the restriction enzyme AseI and tested by use of
PFGE. Products were analyzed for similarities in banding
patterns by use of dendrograms. A similarity
matrix was constructed for isolates, and the matrix
was tested for nonrandom distributions of similarity
values with respect to groupings of interest.
Results—There was little grouping of isolates on the
basis of country, virulence status, or region within
Texas. Isolates of R equi were generally < 80% similar,
as determined by use of PFGE. Isolates from the
same farm generally were rarely of the same strain.
Conclusions and Clinical Relevance—Considerable
chromosomal variability exists among isolates of R
equi obtained from the same farm, sites within Texas,
or among countries from various continents. Only
rarely will it be possible to link infections to a given
site or region on the basis of analysis of isolates by
use of PFGE of chromosomal DNA. (Am J Vet Res 2003;64:153–161)
Objective—To determine comparative efficacy of
vaccines administered IM and intranasally, used alone
or sequentially, to protect puppies from infection with
Bordetella bronchiseptica and determine whether
systemic or mucosal antibody response correlated
Design—Randomized controlled trial.
Animals—50 specific-pathogen-free Beagle puppies.
Procedure—In 2 replicates of 25 dogs each, 14-weekold
puppies that were vaccinated against canine distemper
virus and parvovirus were vaccinated against B bronchiseptica via intranasal, IM, intranasal-IM, or IMintranasal
administration or were unvaccinated controls.
Puppies were challenge exposed via aerosol administration
of B bronchiseptica 2 weeks after final vaccination.
Clinical variables and systemic and mucosal antibody
responses were monitored for 10 days after challenge
exposure. Puppies in replicate 1 were necropsied
for histologic and immunohistochemical studies.
Results—Control puppies that were seronegative
before challenge exposure developed paroxysmal
coughing, signs of depression, anorexia, and fever.
Vaccinated puppies (either vaccine) that were seronegative
before challenge exposure had fewer clinical signs.
Puppies that received both vaccines had the least
severe clinical signs and fewest lesions in the respiratory
tract. Vaccinated dogs had significantly higher concentrations
of B bronchiseptica-reactive antibodies in
serum saliva before and after challenge. Antibody concentrations
were negatively correlated with bacterial
growth in nasal cavity and pharyngeal samples after
Conclusions and Clinical Relevance—Parenterally
and intranasally administered vaccines containing B
bronchiseptica may provide substantial protection
from clinical signs of respiratory tract disease associated
with infection by this bacterium. Administration
of both types of vaccines in sequence afforded the
greatest degree of protection against disease. (J Am
Vet Med Assoc 2001;218:367–375)