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 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.     

Sialoglycoprotease of Pasteurella haemolytica A1: detection of antisialoglycoprotease antibodies in sera of calves.

Log phase culture supernate from Pasteurella haemolytica biotype A, serotype 1 contains a proteolytic enzyme specific for O-sialoglycoproteins. Using two methods, Western immunoblotting and enzyme neutralization assay, it was demonstrated that certain bovine sera from two previous P. haemolytica A1 vaccination and challenge trials contained antibodies (Ab) (isotypes IgG1 and IgG2 on Western immunoblot) to the sialoglycoprotease (Gcp). In these trials, selected calves were vaccinated twice with either the commercial culture supernate vaccine Presponse or given phosphate-buffered saline (PBS). One trial was conducted during spring, P. haem XIX, and the other during the winter, P. haem XXI. Although there was no clear evidence for induction of anti-Gcp in response to vaccination, several calves seroconverted following intrapulmonary challenge with live P. haemolytica A1. This is the first report of anti-Gcp Ab in bovine sera. The results indicated that the Gcp is immunogenic and that the bacterium produces the enzyme in vivo. Further, animals with an anti-Gcp response had less pneumonia at necropsy, suggesting the Gcp may induce protective immunity.     

Colonization of the tonsils of calves with Pasteurella haemolytica.

Tonsils of 10 calves were inoculated with Pasteurella haemolytica (PH) and the degree of colonization was followed by collecting sequential tonsil. wash specimens. Tonsils were colonized for at least 3 weeks after instillation of PH into the tonsillar sinus. Calves with colonized tonsils responded with serum and nasal secretion antibody responses to PH and to leukotoxin. Pasteurella haemolytica was detected in nasal mucus specimens of 2 calves during the week after inoculation of the tonsils, but all other specimens were culture-negative. Infectious bovine rhinotracheitis virus-induced respiratory tract disease 25 days later did not elicit a population increase of PH in the tonsils, and did not elicit shedding of PH in nasal mucus.     

Effects of experimentally induced Pasteurella haemolytica infection in dairy calves on the pharmacokinetics of flumequine

The effect of experimental Pasteurella haemolytica infection on the intravenous and intramuscular pharmacokinetics of flumequine was studied in dairy calves. The plasma concentration-time curve of flumequine after intravenous injection of 5 mg/kg bodyweight flumequine of a 10% solution before and after experimental infection, was best described by a three-compartment open model. After intramuscular injection of the same dosage rate of a 3% flumequine suspension is was best described by the one-compartment open model with first-order absorption. The experimental infection by intratracheal administration of infectious bovine rhinotracheitis (IBR)-virus and 5 days later intrapulmonary administration of Pasteurella haemolytica produced a clear temperature rise and signs of disease expressed as Average Health Status. Subsequently, plasma Fe and Zn concentration decreased after infection. The distribution volumes Vc, Vd(area) and Vd(ss) after infection (0.07 +/- 0.04, 1.38 +/- 0.36 and 0.50 +/- 0.11 l/kg, respectively) were smaller than those before infection, but the differences were not significant (P less than or equal to 0.1). The intravenous AUC infinity was significantly increased (21.86 +/- 3.51 to 33.85 +/- 2.97 mg.h/l, P less than or equal to 0.01) and the total body clearance (ClB) significantly decreased (0.24 +/- 0.02 to 0.15 +/- 0.01, P less than or equal to 0.01) after infection. After intramuscular injection of flumequine at 5 mg/kg as a 3% suspension, only the bioavailability, F, was significantly decreased after infection (78.5 +/- 14.3 to 59.7 +/- 21.2%, P less than or equal to 0.02). However, this had no consequences for the dosage regimen used. The urine concentration ratio flumequine:7-hydroxy-flumequine:conjugated flumequine changed from 2:1:10 before infection to 6:1:15 after infection, which indicates that hydroxylation and glucuronidation as metabolic pathways for flumequine were decreased after Pasteurella sp. infection.     

The immune response to experimental Pasteurella haemolytica infection in calves

Four male dairy calves, ages 1-9 months, were inoculated intratracheally (IT), with log dilutions (1.5 X 10(3)-1.5 X 10(6)) of an isolate of P. haemolytica A-1. Doses of bacteria varied according to ages of the calves, older calves receiving the larger doses. All four calves became severely ill within 24 h after inoculation and antibiotic treatment was considered essential. Two months later the four calves remained healthy after IT injection of P. haemolytica, again given in log dilution (2.8 X 10(2)-2.8 X 10(5)). The control calf, given a dilution of only 28 viable P. haemolytica (plate count), developed severe respiratory infection 9 days post inoculation. Antibiotic treatment was given to this calf for 7 days, at which time recovery was evident. All five calves developed direct bacterial agglutination titers to P. haemolytica. Persistent leukocyte migration inhibition indexes of all calves were decreased by greater than or equal to 20% compared to their controls. Although the initial doses administered were low, the calves became ill. Most reports refer to massive doses necessary to produce primary disease and significant agglutination titers.     

Bovine herpesvirus-1 and Pasteurella haemolytica aerobiology in experimentally infected calves

Eight calves (2 calves in each of 4 groups) were exposed to an aerosol of bovine herpesvirus-1 (BHV-1) and 4 days later to an aerosol of Pasteurella haemolytica. Samples of tracheal and exhaled air were taken simultaneously beginning 1 day before viral exposure and once a day up to 3 to 4 days after the bacterial exposure. Samples were also taken during the period of aerosol exposure. Only 0.04% to 0.42% of P haemolytica-carrying droplets of the bacterial aerosol passed beyond the cranial part of the respiratory tract to the trachea. Nevertheless, numbers of bacteria as few as 1 bacterium/L of tracheal air were sufficient to produce fatal disease in the lungs of BHV-1-infected calves. In 1 of 4 groups, BHV-1 was isolated from most daily samples of exhaled and tracheal air. Pasteurella haemolytica was isolated 7 times more frequently from air when calves were kept at 1 C than when calves were kept at 23 C. The number of P haemolytica-carrying droplets in exhaled air was low (less than 1/L of air); however, samples obtained during the time that calves were coughing contained up to 10 P haemolytica-carrying droplets/L of air. It was learned that the cranial part of the respiratory tract serves as an efficient filter on inhalation and exhalation, but this filter is deficient in the animal when coughing occurs. This process expels infective droplets of size suitable for inhalation by other cattle in close proximity.     

Viral-bacterial pneumonia in calves: duration of the interaction between bovine herpesvirus 1 and Pasteurella haemolytica.

Sixteen six to eight month old beef calves were exposed individually to a five minute aerosol of bovine herpesvirus 1, isolate 108. Aerosol exposure to Pasteurella haemolytica (biotype A, serotype 1) was administered individually for five minutes at either four, ten, 20 or 30 days after the virus. Fibrinous pneumonia and pleuritis occurred in all four groups but were most extensive and severe in those exposed to the virus and bacterium four days apart (the positive controls). Fibrinous pneumonia was associated with persistence of bovine herpesvirus 1 in the respiratory tract despite resolution of virus-induced necrotic lesions of the respiratory mucosa. The results presented here suggest that, although the severity of viral-bacterial synergism may be influenced by virus-induced morphological changes, the continued presence of viral antigens after the resolution of respiratory mucosal lesions may continue to exert some effect on host defenses and disease processes.     

Pasteurella haemolytica serotype 1 colonization of the nasal passages of virus-infected calves

Nasal passages of calves with a virus-induced respiratory tract disease became colonized by Pasteurella haemolytica serotype 1 after they were inoculated intranasally with P haemolytica. Inoculation with infectious bovine rhinotracheitis virus caused a more severe clinical illness and resulted in a greater degree of colonization with P haemolytica than developed after inoculation with parainfluenza-3 virus. Nasal passages of parainfluenza-3 virus-inoculated calves were colonized to a greater degree with P haemolytica than were those of healthy, nonstressed calves. Calves were susceptible to P haemolytica colonization during or shortly after virus-induced illness, even though they had been previously exposed to P haemolytica and had serum antibody and nasal secretion antibody to P haemolytica.     

Response of Pasteurella haemolytica to erythromycin and dexamethasone in calves with established infection.

A subcutaneous soft tissue infection model in calves was used to study the in vivo response of Pasteurella haemolytica to erythromycin and dexamethasone. Two tissue chambers were implanted SC in each of 12 calves. At 45 days after implantation, all tissue chambers were inoculated with an erythromycin-sensitive strain of P haemolytica. Starting 24 hours after inoculation, calves were allotted to 4 groups of equal size and a 2 x 2-factorial arrangement of treatments was applied: 3 calves were given erythromycin (30 mg/kg of body weight, IM, for 5 days), 3 calves were given dexamethasone (0.05 mg/kg, IM, for 2 days), 3 calves were given erythromycin and dexamethasone, and the remaining calves served as nontreated controls. Chamber fluids were tested daily, and the response to treatment was measured. Neither erythromycin nor dexamethasone affected viability or growth of bacteria within tissue chambers. Dexamethasone had no effect on the influx of neutrophils into infected chambers. Despite repeated administration of a high dose of erythromycin and attainment of adequate concentration in serum, erythromycin concentration in chamber fluids did not exceed the minimal inhibitory concentration established in vitro. These results indicate that the clinical efficacy of erythromycin against P haemolytica sequestered in consolidated pneumonic lesions may not be well correlated with predictions based on serum pharmacokinetic and in vitro susceptibility data.     

Exposure of calves to aerosols of parainfluenza-3 virus and Pasteurella haemolytica.

The present study was undertaken to investigate whether sequential exposure to aerosols of parainfluenza-3 virus followed by Pasteurella haemolytica, or P. haemolytica followed by parainfluenza-3 virus, could lead to the production of pulmonary lesions in conventionally-raised calves. Twenty male calves with low serum antibody titres to both organisms were placed in five equal groups. Synergism of parainfluenza-3 virus and P. haemolytica was not demonstrated in any of the sequentially infected groups and pulmonary lesions were mild in all challenged calves. Clinical signs of disease were not present after exposure to parainfluenza-3 virus although the virus was repeatedly isolated from nasal secretions of all inoculated calves. Exposure to P. haemolytica produced a transient response which consisted of increased rectal temperatures and respiratory rates, with a mild neutrophilic leukocytosis and a mild left shift present six hours postinoculation and returning to normal within 24 hours. Results from this study suggest, although do not confirm, that reduced pulmonary clearance of inhaled P. haemolytica in parainfluenza-3 virus infected calves does not necessarily lead to production of severe pulmonary lesions and that previous exposure to aerosols of P. haemolytica may not enhance secondary parainfluenza-3 virus infection.     

Infection of the middle nasal meatus of calves with Pasteurella haemolytica serotype 1

Eight healthy nonstressed calves were inoculated with Pasteurella haemolytica serotype 1, by instilling a broth culture into the middle nasal meatus of the left nostril. The inoculated left nostrils shed P haemolytica from the ventral nasal meatus at a steady rate for a mean of 7 days, whereas the uninoculated right nostrils of the same calves shed P haemolytica sporadically and in lower concentrations. The duration, frequency, and concentration of P haemolytica shed from the inoculated nostrils was significantly (P less than 0.05) greater than from the nostrils of other healthy calves that had been exposed by instilling the culture into the ventral nasal meatus of both nostrils in a previous study. The concentration of antibodies (IgG, IgA, and IgM) to P haemolytica increased significantly (P less than 0.05) in serum and nasal secretions after exposure. Four weeks after initial P haemolytica exposure, calves were exposed to infectious bovine rhinotracheitis virus and became clinically ill. Four calves were induced to shed P haemolytica from both nostrils by the virus infection; thus, they were harboring the bacterium and were susceptible to active recolonization. Four calves were not induced to shed P haemolytica. The apparent reason was not that they were resistant to active colonization, but that they were no longer harboring the bacterium, because they became active shedders after they were reinfected with P haemolytica.     

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.     

Antibody titers to Pasteurella haemolytica A1 in Ontario beef cattle.

Indirect bacterial agglutination titers to Pasteurella haemolytica A1 were determined in serum, thoracic, pericardial, or peritoneal fluid from cattle necropsied as part of the Bruce County Beef Project in 1979-80 and 1980-81. Antibody titers were also assayed in serum from 84 calves on entry to feedlots in the fall of 1979. Titers on entry were low compared to antibody levels at necropsy. Cattle which died with pneumonia, in particular those dying of fibrinous pneumonia (shipping fever), had lower levels of antibody to P. haemolytica than did those dying of other causes.     

Hemodynamic effects of acute pneumonia experimentally induced in newborn calves inoculated with Pasteurella haemolytica

Hemodynamic responses to acute pneumonia and to hypoxia were investigated in 10 newborn calves. Experiments were performed on heparinized, anesthesized and ventilated calves. Control calves were inoculated intratracheally with bovine fetal serum. Pneumonia was induced in treated calves by intratracheal inoculation with P haemolytica suspended in bovine fetal serum. Before inoculation (base line), at the time of inoculation (T = 0), and at 30-minute intervals for 3 hours, pulmonary arterial pressure (Ppa), systemic arterial pressure, cardiac output (CO), arterial blood gases, pulmonary vascular resistance (PVR), and systemic vascular resistance were determined. At T = 0, calves in both groups became hypoxemic, alveolar-arterial O2 difference, PVR, and Ppa increased, and CO and systemic vascular resistance remained unchanged. At subsequent measurement intervals, all values returned to base-line in control calves, whereas treated calves had progressive hypoxemia associated with a decrease in Ppa and PVR, with no change in CO. Three hours after inoculation and after inhalation of 10% O2 in N2, PVR increased significantly in the control calves. In the treated group, hypoxia did not increase the resistance, compared with base-line and 3-hour values. The data indicate decreased Ppa during pneumonic pasteurellosis is because of a decrease in PVR and that pneumonia may attenuate the normal pulmonary hypoxic vasoconstrictor response.