Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Terry L. Bowersock x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract

Objective—To determine the efficacy of a multivalent modified-live virus (MLV) vaccine containing a Mannheimia haemolytica toxoid to reduce pneumonia and mortality rate when administered to calves challenge exposed with virulent Bibersteinia trehalosi.

Animals—74 Holstein calves.

Procedures—Calves were assigned to 2 treatment groups. Calves in the control group (n = 36) were vaccinated by SC administration of 2 mL of a commercial 5-way MLV vaccine, and calves in the other group (38) were vaccinated by SC administration of a 2-mL dose of a 5-way MLV vaccine containing M haemolytica toxoid (day 0). On day 21, calves were transtracheally administered B trehalosi. Serum was obtained for analysis of antibody titers against M haemolytica leukotoxin. Nasopharyngeal swab specimens were collected from calves 1 day before vaccination (day −1) and challenge exposure (day 20) and cultured to detect bacterial respiratory pathogens. Clinical scores, rectal temperature, and death attributable to the challenge-exposure organism were recorded for 6 days after challenge exposure. Remaining calves were euthanized at the end of the study. Necropsy was performed on all calves, and lung lesion scores were recorded.

Results—Calves vaccinated with the MLV vaccine containing M haemolytica toxoid had significantly lower lung lesion scores, mortality rate, and clinical scores for respiratory disease, compared with results for control calves.

Conclusions and Clinical Relevance—Administration of a multivalent MLV vaccine containing M haemolytica toxoid protected calves against challenge exposure with virulent B trehalosi by reducing the mortality rate, lung lesion scores, and clinical scores for respiratory disease.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the effect of vaccination of calves with a killed Mycobacterium avium subsp paratuberculosis (MAP) vaccine on colonization of tissues following oral MAP exposure.

Animals—12 healthy Holstein calves.

Procedures—At 14 days after birth, calves received the MAP vaccine (1.0 mL, SC) or saline (0.9% NaCl) solution (1.0 mL, SC [control treatment]). Each calf received 1.2 × 109 CFUs of live MAP orally 21 and 22 days after vaccination. Prior to vaccination and at subsequent intervals, a blood sample was collected for ELISA detection of antibodies against MAP and for whole blood, antigen-specific, interferon (IFN)-γ–release assay. Nine weeks after MAP challenge, calves were euthanized and various tissue samples were collected for mycobacterial culture. Interferon-γ production in prescapular lymph node cells was measured following in vitro stimulation with MAP antigens.

Results—Calves were seronegative for anti-MAP antibodies at all times. Compared with the findings in control calves, antigen-specific IFN-γ production in circulating lymphocytes and prescapular lymph node cells from vaccinated calves was significantly higher. Culture of tissues from vaccinated calves yielded significantly fewer CFUs of MAP (2,417 CFUs/g), compared with tissues from control calves (15,709 CFUs/g). Furthermore, significantly fewer tissue samples from vaccinated calves yielded MAP in culture (21.8 tissues/calf), compared with findings in control calves (27.6 tissues/calf).

Conclusions and Clinical Relevance—Inoculation of calves with a killed MAP vaccine was associated with reduced colonization of intestinal tissues following experimental exposure to MAP. Use of the vaccine could potentially reduce transmission of MAP to calves in infected herds.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate efficacy and duration of immunity of the bovine herpesvirus type 1 (BHV-1) fraction of a trivalent vaccine also containing parainfluenza virus-3 and bovine respiratory syncytial virus fractions administered intranasally (IN) for protection of calves against infectious bovine rhinotracheitis (IBR).

DESIGN Controlled challenge study.

ANIMALS 120 dairy calves (3 to 8 days old) seronegative for antibody against BHV-1 (experiments 1 and 2) or seropositive for maternally derived antibody against BHV-1 (experiment 3).

PROCEDURES In 3 separate experiments, calves were vaccinated IN via 2 nostrils (experiment 1) or 1 nostril (experiments 2 and 3) with a vaccine containing or not containing a BHV-1 fraction. For seronegative calves, the test vaccine contained a minimum immunizing dose of BHV-1; for seropositive calves, it contained a commercial dose of BHV-1. Calves were challenged IN with virulent BHV-1 on day 28 or 193 (seronegative calves) or day 105 (seropositive calves) after vaccination to evaluate vaccine efficacy. Frequency and duration of clinical signs, rectal temperatures, virus shedding, and serologic responses were compared between treatment groups within experiments.

RESULTS In all experiments, BHV-1 vaccinated calves had lower frequencies or shorter durations of clinical signs of IBR than did control calves. Following viral challenge, peak rectal temperatures and degrees of virus shedding were lower and serologic responses were higher in vaccinated versus control calves.

CONCLUSIONS AND CLINICAL RELEVANCE IN vaccination against BHV-1 protected all calves against clinical IBR disease, regardless of serologic status at the time of vaccination, and suppressed virus shedding. A single dose of this IN vaccine has the potential to protect seronegative calves for at least 193 days and override maternally derived antibody to protect seropositive calves for at least 105 days.

Restricted access
in Journal of the American Veterinary Medical Association