Objective—To evaluate a rapid polymerase chain
reaction (PCR) fingerprinting technique for discriminating
among Pasteurella multocida isolates from laboratory
Sample Population—33 P multocida isolates from
rabbits with clinical pasteurellosis.
Procedure—PCR assays were conducted with 2
minisatellites (core sequence and modified core
sequence of phage M13) and 2 microsatellites
([GTG]5 and [GACA]4). Each bacterium was assigned
to a PCR type for each of the primers used. Boiled
bacterial extracts and purified genomic DNA were
compared by use of PCR assays for phage M13 and
(GACA)4. Plasmids were isolated from each bacterium,
and their influence on PCR fingerprint was determined,
using boiled extracts as a DNA source.
Results—M13 core sequence and M13 modified
core sequence yielded 5 and 8 PCR types, respectively.
The microsatellites (GTG)5 and (GACA)4 yielded
4 and 9 PCR fingerprint types, respectively.
Fingerprint patterns obtained by use of isolated DNA
differed from those obtained by use of boiled
extracts, although discrimination among P multocida
isolates was similar. The presence or absence of plasmids
did not affect PCR fingerprints.
Conclusion—Single primer PCR fingerprinting with
minisatellite and microsatellite primers is an efficient
and reproducible method for the discrimination of
P multocida isolates from rabbits and can be performed
directly, using boiled bacterial extracts as a source of
template, although more bands were obtained from
pure genomic DNA. (Am J Vet Res 2000;61:305–309)
Case Description—A 10-year-old Longhorn cow pregnant with a valuable fetus was evaluated because of progressive inspiratory dyspnea of 6 weeks' duration.
Clinical Findings—Physical examination findings were consistent with upper respiratory tract obstruction. A large pedunculated soft tissue mass was evident in the mid-dorsal aspect of the pharynx during palpation and endoscopic examination. Results of microscopic examination of transendoscopic fine-needle aspirates and a biopsy specimen were suggestive of a bacterial granuloma.
Treatment and Outcome—Transtracheal intubation was performed, and the mass was excised with a chain écraseur. Results of histologic examination were consistent with a diagnosis of actinobacillosis. The owner reported that the cow was doing well without any recurrence of respiratory distress 8 months after surgery.
Clinical Relevance—Findings suggested that pharyngeal granuloma resulting from actinobacillosis should be included in the differential diagnoses when examining mature cattle with upper respiratory tract obstruction and that a chain écraseur may be useful for excising soft tissue pharyngeal masses in cattle.
OBJECTIVE To compare clinical disease and lung lesions in calves experimentally inoculated with Histophilus somni 5 days after metaphylactic administration of tildipirosin or tulathromycin.
ANIMALS Twenty-four 3-month-old Holstein and Holstein-crossbreed steers.
PROCEDURES Calves were randomly allocated to 3 groups of 8 calves. On day 0, calves in group 1 received tildipirosin (4 mg/kg, SC), calves in group 2 received tulathromycin (2.5 mg/kg, SC), and calves in group 3 received isotonic saline (0.9% NaCl) solution (1 mL/45 kg, SC; control). On day 5, calves were inoculated with 10 mL of a solution containing H somni strain 7735 (1.6 × 109 CFUs/mL, intrabronchially; challenge). Calves were clinically evaluated on days 5 through 8 and euthanized on day 8. The lungs were grossly evaluated for evidence of pneumonia, and bronchial secretion samples underwent bacteriologic culture.
RESULTS The mean clinical score for each group was significantly increased 12 hours after challenge, compared with that immediately before challenge, and was significantly lower for tildipirosin-treated calves on days 6, 7, and 8, compared with those for tulathromycin-treated and control calves. The mean percentage of lung consolidation for tildipirosin-treated calves was significantly lower than those for tulathromycin-treated and control calves. Histophilus somni was isolated from the bronchial secretions of some tulathromycin-treated and control calves but was not isolated from tildipirosin-treated calves.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that metaphylactic administration of tildipirosin to calves 5 days prior to H somni challenge prevented subsequent culture of the pathogen from bronchial secretions and was more effective in minimizing clinical disease and lung lesions than was metaphylactic administration of tulathromycin.
Procedure—Calves purchased from an order buyer
were delivered to a feedlot to study the effects of
dietary supplementation with 2,000 IU of vitamin E
for 0, 7, 14, or 28 days after arrival. Serum or plasma
Fib, Hap, SAA, and AGP concentrations were
measured on days 0, 7, and 28 after arrival as well
as at the time of treatment for respiratory tract disease
with antimicrobial drugs and after completion
Results—Vitamin E supplementation was associated
with decreased treatment costs. In cattle that were
not recognized as sick or responded positively to 1
antimicrobial treatment, serum Hap concentrations
were significantly lower on days 0 and 7 than concentrations
for cattle that required > 1 treatment. Serum
Hap concentrations and ratios of Hap to SAA on day 0
significantly correlated with the number of antimicrobial
treatments required. Serum Hap concentrations at
the time of initial treatment were significantly lower
for cattle that required only 1 treatment, compared
with those that required > 1 treatment.
Conclusions and Clinical Relevance—Serum Hap
concentrations are of potential value for use in
assessing feedlot cattle that may become ill as a
result of respiratory tract disease and for use in monitoring
treatment efficacy. (Am J Vet Res 2002;
Objective—To evaluate serum haptoglobin concentration at feedlot arrival and subsequent performance and morbidity and mortality rates of calves that developed bovine respiratory disease.
Animals—360 heifer calves and 416 steer and bull calves.
Procedures—Serum samples were obtained from cattle at the time of arrival to a feedlot (day −1) and analyzed for haptoglobin concentration. In experiment 1, calves were classified into groups with a low (< 1.0 μg/mL), medium (1.0 to 3.0 μg/mL), or high (> 3.0 μg/mL) serum haptoglobin concentration and allotted into pens on the basis of group. In experiment 2, calves were classified as having or not having detectable serum haptoglobin concentrations.
Results—In experiment 1, average daily gain from days 1 to 7 decreased as haptoglobin concentration increased. Dry-matter intake (DMI) from days 1 to 21 decreased with increasing haptoglobin concentration, and DMI typically decreased from days 1 to 63. Total bovine respiratory disease morbidity rate typically increased with increasing haptoglobin concentration. At harvest, no differences in carcass characteristics were observed on the basis of haptoglobin concentration. In experiment 2, cattle with measureable serum haptoglobin concentrations at arrival weighed less throughout the experiment, gained less from days 1 to 7, and had lower DMI from days 1 to 42. Overall morbidity rate was not different between groups, but cattle with detectable serum haptoglobin concentrations had higher odds of being treated 3 times.
Conclusions and Clinical Relevance—Serum haptoglobin concentration in cattle at the time of feedlot arrival was not associated with overall performance but may have limited merit for making decisions regarding targeted prophylactic treatment.
Objective—To evaluate diagnostic tests used for detection of bovine viral diarrhea virus (BVDV) and determine the prevalence of BVDV subtypes 1a, 1b, and 2a in persistently infected (PI) cattle entering a feedlot.
Procedures—Samples were obtained from calves initially testing positive via antigen capture ELISA (ACE) performed on fresh skin (ear notch) specimens, and ACE was repeated. Additionally, immunohistochemistry (IHC) was performed on skin specimens fixed in neutral-buffered 10% formalin, and reverse transcriptase PCR (RT-PCR) assay and virus isolation were performed on serum samples. Virus was subtyped via sequencing of the 5′ untranslated region of the viral genome.
Results—Initial ACE results were positive for BVDV in 88 calves. After subsequent testing, results of ACE, IHC, RT-PCR assay, and viral isolation were positive in 86 of 88 calves; results of all subsequent tests were negative in 2 calves. Those 2 calves had false-positive test results. On the basis of IHC results, 86 of 21,743 calves were PI with BVDV, resulting in a prevalence of 0.4%. Distribution of BVDV subtypes was BVDV1b (77.9%), BVDV1a (11.6%), and BVDV2a (10.5%).
Conclusions and Clinical Relevance—Rapid tests such as ACE permit identification and segregation of PI cattle pending results of further tests, thus reducing their contact with the rest of the feedlot population. Although vaccines with BVDV1a and 2a components are given to cattle entering feedlots, these vaccines may not provide adequate protection against BVDV1b.
Objective—To determine efficacy of intranasal vaccination
of rabbits with Pasteurella multocida A:3 outer
membrane proteins (OMP) expressing iron-regulated
OMP (IROMP) in conferring protection against experimental
Animals—52 male New Zealand White rabbits.
Procedure— Rabbits were vaccinated intranasally on
days 0, 7, and 14; some vaccines included cholera
toxin (CT) as an adjuvant. Concentrations of intranasal
IgA and serum IgG antibodies against P multocida
OMP were determined. In experiment A, rabbits
were vaccinated with either phospate-buffered saline
solution (PBSS), PBSS-CT, OMP-CT, or IROMP-CT,
challenge-exposed intranasally on day 16, and euthanatized
and necropsied on day 28. Rabbits were also
vaccinated with OMP or IROMP without CT and were
not challenge-exposed. In experiment B, rabbits were
vaccinated with PBSS, PBSS-CT, IROMP, or IROMP-CT.
On day 17, rabbits were challenge-exposed
intranasally .Nasal bacteria and antibodies were determined
on day 24.
Results—In experiment A, OMP-CT vaccination stimulated
mucosal and systemic antibody responses to
the bacterium and enhanced resistance against challenge
exposure. Intranasal bacterial counts were not
significantly reduced. Vaccination with IROMP-CT
stimulated mucosal and systemic antibodies,
enhanced resistance to challenge exposure, and significantly
reduced nasal bacterial counts. In experiment
B, natural infection was detected in several rabbits
at challenge exposure; however, IROMP-CT-vaccinated
rabbits had significantly higher serum and nasal
antibody responses, compared with other
rabbitsIROMP-CT-vaccinated rabbits had significantly
lower nasal bacterial counts compared to control rabbits.
Conclusions and Clinical Relevance—Intranasal
vaccination of rabbits with P multocida outer membranes
containing IROMP and CT stimulated immunity
against experimental pneumonic pasteurellosis.
(Am J Vet Res 2001;62:697–703)
Objective—To detect bovine adenovirus serotype 7
(BAV-7) infections in calves by use of viral isolation
and serologic testing.
Animals—205 postweaning calves.
Procedure—121 calves were assembled by an order
buyer through auction markets in eastern Tennessee
and transported to New Mexico where they were
commingled with 84 healthy ranch-reared calves.
Tests included viral isolation in cell culture from
peripheral blood leukocytes (PBL) and detection of
serum BAV-7 antibodies by use of microtitration viral
Results —BAV-7 was isolated from PBL of 8 calves
and seroconversion to BAV-7 was detected for 38 of
199 (19.1%) calves. Concurrent bovine viral diarrhea
virus infections were detected in most calves from
which BAV-7 was isolated.
Conclusions and Clinical Relevance —Results of our
study indicate that BAV-7 infections can be found in
postweaning commingled calves and may develop
more commonly in calves with concurrent infections
with viruses such as bovine viral diarrhea virus
(BVDV). (Am J Vet Res 2002;63:976–978).