Bovine respiratory disease: commercial vaccines currently available in Canada.

Bovine respiratory disease (BRD) remains a significant cost to both the beef and dairy industries. In the United States, an estimated 640 million dollars is lost annually due to BRD. Losses are largely a result of pneumonic pasteurellosis ("shipping fever"), enzootic pneumonia of calves, and atypical interstitial pneumonia. In Canada, over 80% of the biologics licensed for use in cattle are against agents associated with BRD. The objectives of this paper were (a) to summarize information available concerning commercial vaccines currently used in Canada for protection against BRD, and (b) to provide an easily accessible resource for veterinary practitioners and researchers. Information from the most recent Compendium of Veterinary Products has been tabulated for each vaccine by trade name, according to vaccine type, and the pathogens against which they are designed to protect. Additional information from published articles (peer-reviewed and other) has been provided and referenced

Pasteurella haemolytica cytotoxin neutralizing activity in sera from Ontario beef cattle.

A random sample of sera obtained from cattle necropsied as part of the Bruce County Beef Project in 1980-81 was assayed for the ability to neutralize the cytotoxin of Pasteurella haemolytica A1. Cattle dying of fibrinous pneumonia had significantly lower neutralizing activity in serum than cattle which died for reasons other than pneumonia. Activity in pneumonic cattle was also lower than the mean of twelve samples randomly chosen from sera of cattle bled on entry to feedlots in the fall of 1979. A role for the toxin neutralizing response in resistance to pneumonic pasteurellosis is proposed

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

Evidence of bovine immunoglobulin G1 (IgG1) protease activity in partially purified culture supernate of Pasteurella haemolytica A1.

In the bovine respiratory tract, IgG1 is a major secretory immunoglobulin (Ig), and both IgG1 and IgG2 are believed to be important in defense against pneumonic pasteurellosis (shipping fever) in calves. Here we provide evidence for hydrolysis of IgG1 in the presence of partially purified culture supernate (ppCS) from the respiratory pathogen Pasteurella haemolytica A1. Bovine IgG1 was hydrolysed sequentially into three distinct bands (approximately 39, 12, and 7 kDa respectively). Furthermore, partial hydrolysis of bovine IgG2 was observed, but neither bovine IgA nor IgM were affected by incubation with ppCS. These findings suggest that the production of an IgG1-specific protease by P. haemolytica A1 may be a virulence mechanism contributing to the pathogenesis of bovine pneumonic pasteurellosis

Pregnancy failure following vaginal infection of sheep with Chlamydia psittaci prior to breeding.

Enzootic abortion in sheep, caused by Chlamydia psittaci, has been associated with pregnancy failure in most sheep-producing countries. Late-term abortions or the birth of weak low-birth-weight lambs occurred following primary C. psittaci infection in pregnant ewes. However, the mode by which C. psittaci can be transmitted among sheep has not been established. The present study was designed to determine whether the vaginal tracts of nonpregnant ewes were susceptible to C. psittaci infection and whether such infections had an impact during the next pregnancy. At day 0 of the estrus cycle, the vaginal tracts of 10 nonpregnant ewes were inoculated with C. psittaci and 10 ewes were exposed by subcutaneous injection. The ewes were bred 6 weeks postinfection. Five ewes from the vaginally infected group and four from the subcutaneously infected group were reinfected by subcutaneous injection at day 60 of gestation. Pregnancy outcomes and antibody responses to infection were compared with that of ewes that were infected with C. psittaci, either subcutaneously or intravaginally, for the first time during pregnancy and with that of noninfected control ewes. Subcutaneous infection of nonpregnant ewes did not cause subsequent pregnancy failure; rather, this provided protection against abortion following reinfection during pregnancy. As expected, abortions or the birth of weak lambs was observed in those ewes that received primary C. psittaci infection by either route during pregnancy. Similarly, abortion or the birth of weak lambs was a consequence of vaginal inoculation prior to breeding, thereby confirming the susceptibility of the vaginal mucosa to infection and demonstrating the potential for venereal transmission

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

Pasteurella haemolytica leukotoxin induces histamine release from bovine pulmonary mast cells.

Pasteurella haemolytica A1 leukotoxic culture supernatant was evaluated for its ability to induce histamine release from bovine pulmonary mast cells isolated by enzymatic dispersion of lung tissue. Histamine was measured by a radioimmunoassay technique. Leukotoxic culture supernatant of P. haemolytica significantly released histamine in a time and concentration-related manner. This effect was lost when culture supernatant was heat-inactivated or preincubated with leukotoxin neutralizing rabbit serum. Preincubation of the mast cells with propranolol or p-bromophenacyl bromide reduced the histamine-releasing effect of leukotoxin, while verapamil enhanced release. Experimental infection of calves with P. haemolytica A1 reduced the total histamine content of pulmonary mast cells recovered at postmortem. Histamine release induced by P. haemolytica leukotoxin is likely an important factor in the pathogenesis of bovine pneumonic pasteurellosis

Nucleotide sequence of the leukotoxin genes of Pasteurella haemolytica A1.

A 4.4-kilobase-pair DNA fragment coding for the leukotoxin of Pasteurella haemolytica A1 has been isolated, and its nucleotide sequence has been determined. Two open reading frames, designated lktC and lktA, coding for proteins of 19.8 and 101.9 kilodaltons, respectively, were identified. Expression of the two genes in minicell-labeling experiments resulted in the production of the predicted proteins LKTC and LKTA. By using an antiserum against the soluble antigens of P. haemolytica A1 in Western blot (immunoblot) analysis of total cellular proteins from the Escherichia coli clones, LKTA was identified as an additional antigenic protein. Results from subcloning of the DNA fragment suggested that expression from both lktC and lktA is required for leukotoxin activity, indicating that the leukotoxin of P. haemolytica A1 is encoded by two genes. A comparison of the organization and the DNA sequence of the leukotoxin genes with those of the E. coli alpha-hemolysin genes showed a significant degree of homology between the two loci. This analysis suggested that the leukotoxin genes of P. haemolytica A1 and the E. coli alpha-hemolysin genes may have evolved from a common ancestor and that the two toxins may share similar activities or functional domains or both