Effects of various vaccination protocols on passive and active immunity to Pasteurella haemolytica and Haemophilus somnus in beef calves.

Two field trials were conducted in a beef cow herd in Saskatchewan to determine the effectiveness of a combined Pasteurella haemolytica and Haemophilus somnus vaccine in increasing passively and actively acquired antibodies in beef calves. Vaccination of dams at 4 and/or 7 weeks prepartum was associated with increased antibody titers to P. haemolytica and H. somnus in their serum (P < 0.05), colostrum (P < 0.05), and serum of their calves at 3 days and 1 month of age (P < 0.05). There was no significant (P > 0.05) difference in antibody titers in the colostrum and serum of calves from single or double vaccinated dams. Calves vaccinated at 1 and 2 months of age in the face of maternal antibodies to P. haemolytica and H. somnus had significantly (P < 0.05) higher antibodies to P. haemolytica and H. somnus at 4 and 6 months of age than did unvaccinated calves. Calves vaccinated at 3 and 4 months of age in the face of low levels of preexisting antibodies had significantly (P < 0.05) higher antibodies to P. haemolytica at 5 months of age and to H. somnus at 5 and 6 months of age than did unvaccinated calves. Calves vaccinated once at 4 months of age had significantly (P < 0.05) higher antibody titers to P. haemolytica and H. somnus at 4.5 months of age than did unvaccinated calves, but this difference was not apparent at 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vaccination of calves with leukotoxic culture supernatant from Pasteurella haemolytica.

In three experiments subcutaneous vaccination of calves with adjuvanted bacteria-free leukotoxic culture supernatant from log phase cultures of Pasteurella haemolytica A1 (toxin 1) was shown to induce some protection against intrabronchial challenge with live P. haemolytica A1. This toxin 1 vaccine was as effective as a whole cell bacterin in stimulating agglutinating antibody to P. haemolytica. Induction of leukotoxin neutralizing activity was variable; in some cases vaccination only primed the animal to produce an anamnestic response after challenge, whereas in other instances antitoxic activity increased in response to immunization. Two doses of vaccine were shown to be more effective than a single immunization. Vaccination with leukotoxic culture supernatant from the nonpathogenic P. haemolytica serotype 11 was as effective as vaccination with toxin 1 in stimulating antitoxic activity but was not protective. This implies that both serospecific agglutinating activity and an antitoxic response are needed for immunity.     

Immunologic response to Pasteurella haemolytica and resistance against experimental bovine pneumonic pasteurellosis, induced by bacterins in oil adjuvants

Immunogenicity of and protection afforded by Pasteurella haemolytica bacterins were studied in calves. Bacterins contained an aluminum hydroxide in gel (ALH) adjuvant or one of the following oil-in-water adjuvants: Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA), and trehalose dimycolate (TDM). On days 0 and 7, calves were vaccinated with phosphate-buffered saline solution (PBSS), a bacterin, or live P haemolytica. Transthoracic intrapulmonic challenge exposure was done on day 21. In 3 experiments, there were no significant (P greater than 0.05) differences between lung lesions induced in PBSS-or ALH bacterin-vaccinated calves. Both FCA and FIA bacterins significantly (P less than 0.05) enhanced resistance against challenge exposure. Resistance induced by FCA and FIA bacterins was comparable with that induced by vaccination with live P haemolytica. Calves vaccinated with FIA bacterin and challenge-exposed to P haemolytica at a concentration of 4.5 X 10(9) colony-forming units (4.5 times greater than used in the first 3 experiments) resisted challenge exposure similar to calves given live organisms. The TDM bacterin failed to enhance resistance. All bacterins caused a significant increase (P less than 0.05) in serum antibody to P haemolytica somatic antigens, as measured by a quantitative fluorometric immunoassay. Pasteurella haemolytica leukotoxin neutralizing antibody titers did not increase significantly (P greater than 0.05) in sera after vaccination with any bacterin. Vaccination with FCA and FIA bacterins resulted in a significant increase (P less than 0.001) in serum antibody to a carbohydrate-protein subunit of P haemolytica, as measured by an enzyme-linked immunosorbent assay.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of route and dosage of immunization on the serological response to a Pasteurella haemolytica and Haemophilus somnus vaccine in feedlot calves

The effect of route and dosage of administration on the serological response to a vaccine containing genetically attenuated leukotoxin of Pasteurella haemolytica combined with bacterial extracts of P. haemolytica and Haemophilus somnus (Somnu-Star Ph, Biostar Inc., Saskatoon, Saskatchewan) was evaluated in a controlled field trial in 301 feedlot calves. Vaccination of calves on arrival at the feedlot with Somnu-Star Ph significantly (p < 0.05) increased P. haemolytica and H. somnus serum antibody titers and reduced bovine respiratory disease (BRD) morbidity. A single subcutaneous vaccination with Somnu-Star Ph was as effective in stimulating a humoral antibody response and in reducing BRD morbidity as double vaccination by the intramuscular or the subcutaneous route. Furthermore, there were no swellings or adverse reactions observed with either subcutaneous or intramuscular administration of Somnu-Star Ph.

These results suggest that feedlot calves can be immunized subcutaneously once on arrival with Somnu-Star Ph. Double vaccination was of no added value in this trial, because the majority of BRD morbidity occurred prior to revaccination fourteen days postarrival. Additional larger-sized field trials are needed to monitor the duration of immunity following vaccination and to test the effect of route and dosage of vaccination on mortality.

     

Serum and colostrum antibody to Pasteurella species in dairy cattle

A survey of antibody to Pasteurella haemolytica and P multocida, using a fluorometric immunoassay, was conducted on sera collected from 264 dairy cattle from 3 herds. Serum antibody titers to P haemolytica were 0 to 270 with low titers (less than 25) seen in 48.1% of the cows and heifers. Serum antibody titers to P multocida were 0 to 380 and the frequency of distribution of these titers were more even than for P haemolytica. Mean serum antibody titers to P haemolytica were significantly (P less than 0.005) higher in cattle from an open dairy herd when compared with those from 2 closed herds. Antibody titers to these organisms was determined in 7 colostrum samples. Pasteurella haemolytica antibody titers varied, depending on the whey separation technique used. Passive transfer of colostrum-derived antibody in 5 neonatal calves resulted in a maximum mean serum antibody titer at 20 hours after birth for P haemolytica and at 8 hours after birth for P multocida. Serum titers were higher overall for P multocida than for P haemolytica. Serum titers for P haemolytica declined rapidly. A significant (P less than 0.05) increase in antibody to P multocida was observed at 5 days of age.     

Pulmonary immunity in calves following stimulation of the gut-associated lymphatic tissue by bacterial exotoxin.

Antibodies in serum and pulmonary lavage fluids were measured in calves following stimulation of the gut-associated lymphatic tissue (GALT) by inoculation of crude leukotoxin of Pasteurella haemolytica into the duodenum through a surgically placed catheter. Nine calves free of P. haemolytica were divided into two groups. Group 1 received an intraduodenal (ID) inoculation of leukotoxin and group 2 received an ID inoculation of phosphate buffered saline. Serum and pulmonary lavage fluids were collected weekly and assayed for antibodies specific to P. haemolytica including immunoglobulin (Ig)G, leukotoxin neutralizing antibodies (LNA), and IgA (lavage fluids only). The multiplicative increase (over baseline) in each class of antibody titer following ID inoculation of leukotoxin, the composite geometric mean increase of all antibodies together, and the composite number of the five antibody titers which increased at least fourfold were computed. Results showed that the geometric mean of each antibody titer and the two composite indices was higher in the GALT-primed groups than in the sham-primed group. The differences were statistically significant (p less than 0.05) for serum IgG and for the two composite indices. This experiment demonstrates for the first time that GALT stimulation by bacterial exotoxins results in increased pulmonary antibody levels in calves.     

Maternally and naturally acquired antibodies to Mannheimia haemolytica and Pasteurella multocida in beef calves

The dynamics and duration of maternally derived antibodies as well as the onset of acquired immunity against Mannheimia haemolytica and Pasteurella multocida in range-pastured beef calves were investigated. Two groups of unvaccinated cattle were used in this study. Serum antibody responses were measured by enzyme-linked immunoassay for antibodies of the IgG1, IgG2 and IgM isotypes binding M. haemolytica whole cells (WC) or leukotoxin (LKT) and P. multocida outer membrane proteins (OMPs). Comparisons of mean antibody responses to M. haemolytica LKT and WC and P. multocida OMPs were made within each group. Maternally derived antibodies against M. haemolytica and P. multocida reached lowest levels at 30-90 days after birth. Calves began production of antibodies against M. haemolytica and P. multocida between 60 and 90 days of age in both groups. Based on the results of this study, in beef herds vaccinated against M. haemolytica and/or P. multocida, it may be best to vaccinate calves around 3 months of age. In contrast, beef calves from unvaccinated herds might benefit from vaccination at 4 months of age.     

The effect of subunit or modified live bovine herpesvirus-1 vaccines on the efficacy of a recombinant Pasteurella haemolytica vaccine for the prevention of respiratory disease in feedlot calves

The efficacy of a Pasteurella haemolytica vaccine (PhV) administered once to calves within 24 hours of arrival at a feedlot was tested for the ability to prevent morbidity and mortality from all bovine respiratory disease (BRD) and specifically from fibrinous pneumonia mortality. The PhV consisted of two immunizing ingredients: outer membrane proteins extracted from P. haemolytica, plus genetically attenuated leukotoxin produced by recombinant DNA technology. This double blind study was conducted at a large Saskatchewan feedlot using 2,324 high-risk calves purchased at auction markets and kept under typical commercial feedlot conditions. The trial design included four vaccine test groups: 1) PhV and a bovine herpesvirus type-1 (BHV-1) subunit vaccine comprised only of the virus glycoprotein IV (gIV); 2) PhV and a commercial modified live vaccine (MLV) containing BHV-1 and parainfluenza-3 viruses; 3) gIV alone; and 4) MLV alone. Calves were assigned to vaccine groups in a random systematic manner, individually identified, and monitored for 90 days after vaccination. The vaccines were given once, on arrival, to reflect common feedlot practice, although vaccination prior to expected risk would be more appropriate.

The PhV in combination with gIV reduced BRD morbidity by 20% (p < 0.05) compared to gIV alone and 24% (p < 0.05) compared to MLV alone, and reduced BRD mortality by 88% (p < 0.05) and fibrinous pneumonia mortality by 100% (p < 0.05) when compared to either gIV or MLV alone. Vaccination with PhV in combination with MLV significantly reduced the efficacy of the PhV in preventing BRD morbidity, BRD mortality, and fibrinous pneumonia mortality and also reduced the antibody response to P. haemolytica leukotoxin. These results suggest that the MLV interfered with the protective capacity of the PhV.

     

Sequential titration of bovine lung and serum antibodies after parenteral or pulmonary inoculation with Pasteurella haemolytica

Calves were vaccinated by intrabronchial or subcutaneous injection of formalinized Pasteurella haemolytica. Antibody in serum, nasal washings, and bronchoalveolar washings was titrated sequentially before and after calves were vaccinated and then challenge exposed with live homologous bacteria. Bronchoalveolar washings were collected by fiberoptics bronchoscopy, and antibody was titrated by indirect (antiglobulin) bacterial agglutination. Responsiveness to vaccination was related in initial serum antibody concentrations. Calves with serum antibody titers of 1:20 or more were nonresponsive, whereas with few exceptions, calves having titers of less than 1:20 responded to vaccination. Results indicated that serum and lung antibody were induced by subcutaneous or by intrabronchial inoculation of formalinized P haemolytica. By either route of immunization, serum antibody was more persistent than was lung antibody, and pulmonary challenge exposure with live P haemolytica did not alter existing titers.     

Antileukotoxin antibody produced in the bovine lung after aerosol exposure to viable Pasteurella haemolytica

Experiments were performed to determine the in vivo immunogenicity of Pasteurella haemolytica leukotoxin. Calves were exposed twice to aerosol mists of viable P haemolytica, using a treatment regimen previously shown to induce a resistant state. Pulmonary lavage fluids and serum samples from these calves were assayed for leukotoxin-neutralizing antibodies. Before aerosol exposure, neutralizing antibody titers were routinely found in serum samples, but were not detectable in pulmonary lavage concentrates before exposure. After aerosol exposure, titers of toxin-neutralizing immunoglobulin (Ig)A and IgG antibodies were found in pulmonary lavage concentrates and were accompanied by increased serum toxin neutralization titers.     

Isolation of Pasteurella haemolytica and correlation with serum antibody response in clinically normal beef calves

Bacteria from the nasal cavity and trachea were cultured, and serum antibody titers determined for Pasteurella haemolytica serotype 1 in 164 beef calves obtained from a closed herd on range pasture. At the first sampling, P. haemolytica serotype 1 was cultured from 16.4% of the calves. Antibody titers were determined by a quantitative fluorimetric method and the mean titer was 9.5 +/- 5.8. Fifty-seven randomly selected calves were used to study the correlation of serum antibody response and positive culture of P. haemolytica under natural conditions. Clinical signs of respiratory disease were not observed in those calves. During the observation periods, there was a two-fold increase in the percentage of calves that were culture positive. There was no significant difference between mean serum antibody titers or frequency distribution of antibody titers from the two samplings. Comparisons between serum antibody titers, rise in titers, and P. haemolytica isolation failed to reveal any significant correlation. Of the 9 calves that had a decline in antibody titer to P. haemolytica, none was culture positive. Seroconversion to respiratory viruses did not correlate with P. haemolytica related variables.     

Effect of supplemental chromium on antibody responses of newly arrived feeder calves to vaccines and ovalbumin.

Two trials were conducted to investigate the effects of supplemental chromium (Cr) from organic sources (Cr chelate and high Cr yeast) on antibody responses of newly arrived feeder calves following vaccination with infectious bovine rhinotracheitis (IBR), para-influenza-3 (PI3), bovine respiratory syncytial virus (BRSV), bovine viral diarrhea (BVD) and Pasteurella haemolytica and ovalbumin (OVA). Using cross bred steer calves purchased at sales in Ontario, vaccines and OVA were given on d 0 and 21 after arrival in the feedlot. Immune responses of calves were measured as serum specific antibody titres against all antigens on d 0 and 28 or d 35. The anti-OVA antibody responses (trial 2) were further investigated by measuring antibody concentrations of calves weekly until d 55 after arrival in the feedlot. Supplemental Cr (0.14 ppm) from an amino acid-chelated source had no effect on antibody responses to IBR, P13 and BRSV, but enhanced (P < 0.05) antibody titres of calves in response to the BVD vaccine on d 28 or d 35. Supplemental Cr from Cr yeast had no effect on antibody titres of calves to any vaccines. Chromium from both sources (trial 1 and 2) had no effect on antibody responses of calves following vaccination with P. haemolytica. However, supplemental Cr (0.75 ppm) from Cr yeast enhanced (P < 0.05) serum antibody responses of calves to OVA during the primary response (d 14) and secondary response (d 35) following immunization. These data confirmed our previous finding that supplemental Cr can enhance humoral immune response of market-transit stressed calves, but its enhancement on vaccine efficacy was antigen-dependent and variable.     

Concentration and heritability of immunoglobulin G and natural antibody immunoglobulin M in dairy and beef colostrum along with serum total protein in their calves

Immunoglobulin (Ig) G and natural antibody (NAb) IgM are passively transferred to the neonatal calf through bovine colostrum. Maternal IgG provides pathogen- or vaccine-specific protection and comprises about 85% of colostral Ig. NAb-IgM is less abundant but provides broad and nonspecific reactivity, potentially contributing to protection against the dissemination of pathogens in the blood (septicemia) in a calf’s first days of life. In the dairy and beef industries, failure of passive transfer (FPT) of colostral Ig (serum total protein [STP] <5.2 g/dL) is still a common concern. The objectives of this study were to: (1) compare colostral IgG concentrations and NAb-IgM titers between dairy and beef cows; (2) assess the effect of beef breed on colostral IgG; (3) compare passive transfer of colostral Ig in dairy and beef calves; and (4) estimate the heritability of colostral IgG and NAb-IgM. Colostrum was collected from Holstein dairy (n = 282) and crossbred beef (n = 168) cows at the University of Guelph dairy and beef research centers. Colostral IgG was quantified by radial immunodiffusion and NAb-IgM was quantified by an enzyme-linked immunosorbent assay. In dairy (n = 308) and beef (n = 169) calves, STP was estimated by digital refractometry. Beef cows had significantly greater colostral IgG (146.5 ± 9.5 standard error of the mean [SEM] g/L) than dairy cows (92.4 ± 5.2 g/L, P <0.01). Beef cows with a higher proportion of Angus ancestry had significantly lower colostral IgG (125.5 ± 5.8 g/L) than cows grouped as “Other” (142.5 ± 4.9 g/L, P = 0.02). Using the FPT cutoff, 13% of dairy and 16% of beef calves had FPT; still, beef calves had a significantly larger proportion with excellent passive transfer (STP ≥6.2 g/dL, P <0.01). The heritability of colostral IgG was 0.04 (±0.14) in dairy and 0.14 (±0.32) in beef. Colostral NAb-IgM titers in dairy (12.12 ± 0.22, log₂ [reciprocal of titer]) and beef cows (12.03 ± 0.19) did not differ significantly (P = 0.71). The range of NAb-IgM titers was 9.18–14.60, equivalent to a 42-fold range in antibody concentration. The heritability of colostral NAb was 0.24 (±0.16) in dairy and 0.11 (±0.19) in beef cows. This study is the first to compare colostral NAb-IgM between dairy and beef cows. Based on the range in NAb-IgM titers and the heritability, selective breeding may improve colostrum quality and protection for neonatal calves in the early days of life.     

Serodiagnosis of Salmonella dublin infection in Danish dairy herds using O-antigen based enzyme-linked immunosorbent assay.

Usefulness of two enzyme-linked immunosorbent assays (ELISA) for screening of dairy herds for antibodies to lipopolysaccharide (LPS) of Salmonella dublin (O:1,9,12) was investigated. Sera (3097) were collected from 40 dairy herds located in three areas of Denmark with different prevalence of salmonellosis: ten salmonellosis-free herds from the island of Samsø where there is no history of salmonellosis, ten salmonellosis-free herds from the island of Sealand where outbreaks are infrequent, and 20 salmonella infected herds from Jutland where salmonellosis is enzootic. The samples were analyzed for antibodies to S. dublin LPS using an indirect (O:9,12) and a blocking (O:9) ELISA. Using herd history of salmonellosis, herd location and clinical state of the herds as reference, the herd sensitivity and herd specificity of the tests were 100% and 100% in the indirect ELISA and 95% and 100% in the blocking ELISA, respectively. A significant correlation was found between the two tests (rs = 0.46, p < 0.001). However, the indirect ELISA detected more seropositive animals than the blocking ELISA (17% vs. 7%, respectively). In calves from Sealand, level of background reaction was significantly lower (p < 0.001) compared to the heifers and the cows. The percentages of seropositive calves in both tests were higher (p < 0.01) in comparison to cows (19 vs. 8 in indirect ELISA, and 14 vs. 6 in blocking ELISA, respectively). Results of the study indicated that it is possible to apply LPS ELISA in serological screening for salmonellosis.     

Characterization of Pasteurella spp isolated from healthy domestic pack goats and evaluation of the effects of a commercial Pasteurella vaccine

OBJECTIVE: To characterize Pasteurella spp isolated from healthy pack goats and evaluate the effects of administration of a commercial Pasteurella vaccine. ANIMALS: 45 goats. PROCEDURE: Pharyngeal swab specimens and blood samples were collected on day 0 before vaccination with a Pasteurella (Mannheimia) haemolytica serotype A1 bacterin. Samples were also collected from 17 goats on days 21 and 35. Isolated Pasteurella spp were assigned to biovariant groups on the basis of results of biochemical utilization tests and serotyped. Serum antibody titers were determined. RESULTS: Multiple strains of Pasteurella spp were isolated from swab specimens and assigned to 30 nonhemolytic and 14 beta-hemolytic biovariant groups. The most common biovariant isolated was nonhemolytic P trehalosi belonging to group 2. This strain was isolated from 41 goats. Nonhemolytic P haemolytica strains were isolated from 31 goats, whereas beta-hemolytic strains of P trehalosi and P haemolytica were isolated from 8 and 35 goats, respectively. Vaccination with the A1 serotype did not affect the proportion of goats from which we isolated each biovariant group or the number of biovariant groups isolated. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple strains of P haemolytica and P trehalosi belonging to nonhemolytic and beta-hemolytic biovariant groups were isolated from the pharynx of healthy domestic pack goats. Because hemolytic activity correlates with leukotoxin production, beta-hemolytic strains may have a greater potential to cause disease in naive populations of wild ruminants. However, vaccination with an A1 serotype bacterin did not decrease the proportion of culture-positive goats.     

Induction of pulmonary antibodies to Pasteurella haemolytica following intraduodenal stimulation of the gut-associated lymphatic tissue in cattle.

The induction of pulmonary antibodies to a bacterial antigen following intraduodenal (D) stimulation of the gut-associated lymphatic tissue (GALT) was investigated. Six calves were divided into two groups of three calves each. The GALT-primed calves received an ID dose of live Pasteurella haemolytica A1 followed by a subcutaneous (SC) dose of killed P. haemolytica. The sham-primed calves received an ID dose of phosphate-buffered saline solution (PBSS) followed by a SC dose of killed bacteria. Serum and pulmonary lavage fluids were collected weekly from each calf and assayed for titers of leukotoxin neutralizing antibodies (LNA), as well as IgG and IgA (lavage fluids only) to P. haemolytica. The GALT-primed calves responded to the ID stimulation by bacteria with increased serum IgG. The sham-primed calves had no change in antibody titers following ID stimulation. The GALT-primed calves had increased serum IgG, lavage IgG and IgA and increased LNA titers in both lavage fluids and serum following the SC dose of killed bacteria. The sham-primed calves demonstrated only an increase in serum IgG following the SC inoculation. A challenge study to evaluate if antibodies induced by GALT stimulation could reduce pulmonary lesions was performed using six calves divided into two groups. One group received an ID dose of P. haemolytica followed two weeks later by a SC dose of killed P. haemolytica. The sham vaccinated calves received an ID dose of PBSS followed in two weeks by a SC dose of killed bacterin. Calves were challenged by an intrapulmonary dose of live P. haemolytica A1 eleven days after the SC inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serological titers to bovine herpesvirus 1, bovine viral diarrhea virus, parainfluenza 3 virus, bovine respiratory syncytial virus and Pasteurella haemolytica in feedlot calves with respiratory disease: associations with bacteriological and pulmonary cytological variables.

Acute and convalescent serum samples were taken from 59 calves with signs of respiratory disease (cases) and 60 clinically normal animals (controls) during their first month in the feedlot. Sera were analyzed for antibodies to bovine parainfluenza 3 (PI3) virus by hemagglutination inhibition, to bovine viral diarrhea (BVD) virus, bovine respiratory syncytial (BRS) virus and bovine herpesvirus 1 (BHV1) by virus neutralization, and to Pasteurella haemolytica by indirect agglutination (PhIA) and cytotoxin neutralization (PhCN) tests. There was minimal evidence of serological activity to BHV1. Serological activity to the other agents occurred commonly and the prevalence of acute titers and their mean values was similar in case and control groups. Mean convalescent PI3 and P. haemolytica (PhIA) titers were higher in controls than cases (p < 0.01) but, otherwise, convalescent titers did not differ between groups. The incidence of seroconversion was similar in both groups for all agents except for PI3 virus which was more frequent in controls than cases (p < 0.0001). There was a positive association between PhIA and CN seroconversion and isolation of P. haemolytica from bronchoalveolar lavage (BAL) fluid (p < 0.1). The measure of agreement (kappa) between seroconversion with the P. haemolytica PhIA and PhCN tests was 0.51. Bacteriological and cytological evaluations of the respiratory tract were made using BAL. No associations were evident between serological titers and pulmonary cytology. A multivariate logistic analysis was used to evaluate associations between disease status and serological, bacteriological and cytological data. Cases were positively associated with the presence of neutrophils and Pasteurella multocida in BAL fluid and negatively associated with PI3 virus and PhIA seroconversion.     

Vaccination of neonatal colostrum-deprived calves against Pasteurella haemolytica A1.

Colostrum-deprived Holstein calves were vaccinated at 2 and 4 wk of age with a Pasteurella haemolytica A1 culture supernatant vaccine to determine whether active immune responses and protection could be induced in this age group in the absence of maternal antibodies. All calves responded to vaccination with high titers of IgM antibodies to capsular polysaccharide within 1 wk of primary vaccination. Mean titers of IgG1 and IgG2 antibodies to this antigen increased significantly by 2 wk after secondary vaccination, but peak antibody titers were low. All of the vaccinated calves seroconverted with production of leukotoxin-neutralizing antibodies, but peak antibody titers were low. Vaccinated calves experienced considerable lung damage after experimental challenge, but survival rate, clinical scores, and percent lung involvement were significantly better than those of control (placebo-injected) calves.     

Development and evaluation of an enzyme-linked immunosorbent assay for bovine antibody (IgG) to Pasteurella haemolytica

The sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) for bovine IgG serum antibody to Pasteurella haemolytica was compared with that of an indirect hemagglutination (IHA) test. Pasteurella haemolytica serotypes were grown in a chemically defined cell culture medium, and soluble antigens released into the growth medium were used in the ELISA and IHA test. An ELISA with serotype-1 antigen consistently detected antibody in sera that were positive by IHA test (correlation, 99%). Sera reacting with serotype-1 ELISA antigens also reacted with ELISA antigens prepared from other serotypes. Although ELISA titers averaged 5 log2 units higher than IHA titers, plots of titers determined by the 2 methods were approximately linear. Titer increases detected in paired serum samples by either test were similar. The ELISA was more sensitive than was the IHA in detecting colostral IgG antibody in serum of newborn calves. The ELISA uses a simple, stable antigen preparation and detects antibody to P haemolytica serotypes that commonly infect cattle.     

Effect of vaccination with live or killed Pasteurella haemolytica on resistance to experimental bovine pneumonic pasteurellosis

Using 6- to 8-month-old beef calves, 3 experiments were conducted to compare the effect of vaccination with live or killed Pasteurella haemolytica on resistance to a transthoracic challenge exposure with the organism and to correlate serum antibody response with resistance. In each experiment, calves were vaccinated twice at 1-week intervals and were challenge exposed 21 days after the first inoculation. Lung lesions were evaluated by a system, such that higher scores indicated the more severe lesions. In each experiment, calves immunized with live P haemolytica had lower lesion scores than calves vaccinated with saline solution or bacterin. In 2 of the experiments, the differences were significant (P less than 0.05). In all experiments, calves vaccinated parenterally with a commercial P haemolytica/P multocida bacterin or with a formalin-killed P haemolytica bacterin had lesion scores that were not significantly different (P greater than 0.05) than for control calves vaccinated with saline solution. Live and killed bacterial preparations induced a significant serum antibody response to P haemolytica as measured by a quantitative fluorometric immunoassay. The antibody response to vaccination was not affected by preexisting titers to P haemolytica. Serum antibody titers were not consistently as high for calves vaccinated with bacterins as for calves vaccinated with live organisms. Although high antibody titers correlated with low lesion scores when calves vaccinated with saline solution or live organisms were analyzed collectively, there was not a significant correlation between the 2 variables when calves, vaccinated with saline solution or with bacterin, were analyzed collectively. These data indicate that, although bacterins may induce a detectable serum antibody response, they do not induce protection against transthoracic challenge exposure to P haemolytica.