Objective—To develop and validate an ex vivo model
for study of adherence of Mannheimia haemolytica
(formerly Pasteurella haemolytica) to respiratory tract
mucosa of cattle and to use this model to confirm
adherence of M haemolytica serovar 1 (Mh1) to several
relevant respiratory mucosal surfaces.
Sample Population—Excised nasal, nasopharyngeal,
turbinate, and tonsillar mucosal tissue from the
bovine upper respiratory tract.
Procedure—Mh1 was radiolabeled by use of tritiated
leucine. Various concentrations of labeled bacteria
were incubated with bovine upper respiratory tract
tissues for various times. Tissue was washed to
remove nonadherent bacteria, and percentage of bacteria
adhered (percentage of adherence) was estimated
using radioactivity. Using an optimal inoculum
concentration and incubation time, percentage of
Mh1 adherence was compared on nasal, nasopharyngeal,
turbinate, and tonsillar mucosal tissue, and
adherence to nasopharyngeal tissue was confirmed
by scanning and transmission electron microscopy.
Results—The optimal Mh1 inoculum concentration
was 1 × 107 colony forming units/ml and incubation
time was 3 hours. Percentage of adherence of Mh1
to nasopharyngeal tissue was greater than adherence
to other tissue types.
Conclusions and Clinical Relevance—The ex vivo
model maintained the functional and structural integrity
of bovine upper respiratory tract mucosa, as confirmed
by light and electron microscopy. Electron
microscopy revealed participation of epithelial cell cilia
and surface mucus in adherence of Mh1 to nasopharyngeal
tissue. Adherence of Mh1 was confirmed in
repeated assays, indicating that this organism
adheres to upper respiratory tract mucosa of cattle.
(Am J Vet Res 2001;62:805–811)
Objective—To determine the seroprevalence of antibodies against Leptospira serovars among veterinarians and identify risk factors for seropositivity in veterinary care settings.
Study Population—Veterinarians attending the 2006 AVMA Annual Convention.
Procedures—Blood samples were collected from 511 veterinarians, and serum was harvested for a microcapsule agglutination test (MAT) to detect antibodies against 6 serovars of Leptospira. Aggregate data analysis was performed to determine the ratio of the odds of a given exposure (eg, types of animals treated or biosafety practices) in seropositive individuals to the odds in seronegative individuals.
Results—Evidence of previous leptospiral infection was detected in 2.5% of veterinarians. Most veterinarians reported multiple potential exposures to Leptospira spp and other pathogens in the previous 12 months, including unintentional needlestick injuries (379/511 [74.2%]), animal bites (345/511 [67.5%]), and animal scratches (451/511 [88.3%]). Treatment of a dog with an influenza-like illness within the past year was associated with seropositivity for antibodies against Leptospira spp.
Conclusions and Clinical Relevance—Veterinarians are at risk for leptospirosis and should take measures to decrease potential exposure to infectious agents in general. Diagnostic tests for leptospirosis should be considered when veterinarians have febrile illnesses of unknown origin.
Objective—To compare immune responses following modified-live virus (MLV) vaccination at weaning after intranasal or SC administration of an MLV vaccine to beef calves at 2 or 70 days of age.
Procedures—Calves were allocated to 1 of 5 groups. The IN2 (n = 37) and IN70 (37) groups received an MLV vaccine containing bovine herpesvirus 1 (BHV1), bovine viral diarrhea virus (BVDV) types 1 and 2, bovine respiratory syncytial virus (BRSV), and parainfluenza 3 virus intranasally and a Mannheimia haemolytica and Pasteurella multocida bacterin SC at median ages of 2 and 70 days, respectively. The SC2 (n = 36) and SC70 (37) groups received a 7-way MLV vaccine containing BHV1, BVDV1, BVDV2, BRSV, parainfluenza 3 virus, M haemolytica, and P multocida SC at median ages of 2 and 70 days, respectively; the control group (37) remained unvaccinated until weaning. All calves received the 7-way MLV vaccine SC at median ages of 217 (weaning) and 231 days. Serum neutralizing antibody (SNA) titers against BHV1, BVDV1, and BRSV and intranasal IgA concentrations were determined at median ages of 2, 70, 140, 217, and 262 days. Cell-mediated immunity (CMI) against BHV1, BRSV, BVDV1, and P multocida was determined for 16 calves/group.
Results—At median ages of 140 and 217 days, BVDV1 SNA titers were significantly higher for the SC70 group than those for the other groups. Intranasal IgA concentrations and CMI increased over time for all groups. Vaccination at weaning increased SNA titers and CMI in all groups.
Conclusions and Clinical Relevance—SC administration of an MLV vaccine to 70-day-old calves significantly increased BVDV1 antibody titers before weaning.
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).
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 compare antibody responses, feedlot morbidity and mortality rates, feedlot performance, and carcass value for calves vaccinated with 1 of 2 vaccination strategies and for unvaccinated control calves.
Design—Randomized controlled clinical trial.
Animals—451 beef steers and heifers.
Procedures—Calves were vaccinated with a modified-live infectious bovine rhinotracheitis virus (IBRV), bovine viral diarrhea virus types 1 (BVDV1) and 2 (BVDV2), parainfluenza type 3 virus, and bovine respiratory syncytial virus vaccine and Mannheimia haemolytica and Pasteurella multocida bacterin-toxoid at approximately 67 and 190 days of age (group 1; n = 151) or at approximately 167 and 190 days of age (group 2; 150) or were not vaccinated (control; 150). Serum antibody titers were measured at approximately 2, 67, 167, 190, and 232 days of age. Morbidity and mortality rates, feedlot performance, and carcass value were recorded for 361 calves shipped to feedlots.
Results—Percentages of calves seroconverting to IBRV, BVDV1, and BVDV2 were significantly higher for groups 1 and 2 than for the control group. Mean treatment costs were significantly lower for vaccinated than for control calves, and mean mortality rate was significantly higher for control calves than for group 1 calves. Feedlot performance and carcass value did not vary significantly among groups.
Conclusions and Clinical Relevance—Results suggested that vaccination of beef calves with a 5-antigen modified-live virus vaccine at 67 and 190 days of age was as effective in terms of immunologic responses as was vaccination at 167 and 190 days of age.