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PubMed1984

Experimental production of bovine pneumonic pasteurellosis.

Pneumonic pasteurellosis has been reproduced in conventional, weaned, Friesian-cross calves using a strain of Pasteurella haemolytica biotype A, serotype 1 (P haemolytica A1) isolated from a pathologically confirmed incident of bovine pneumonic pasteurellosis. The major clinical findings were pyrexia, hyperpnoea, tachypnoea, nasal discharge and reduced appetite. Fibrinous pneumonia was present in the lungs of animals at necropsy on days 2 and 3 after initial infection while by days 9 and 10 after initial infection many of the areas of fibrinous pneumonia were confined by a fibrous capsule forming well defined nodules. During the experiment natural transmission of the infecting strain of P haemolytica A1 occurred in two control calves which developed a condition identical to that in the artificially infected calves. P haemolytica A1 was repeatedly recovered from the nasopharynx of infected calves and at necropsy throughout the upper and lower respiratory tracts. Seroconversion, as measured by indirect haemagglutination, to the organism developed in all infected calves by days 9 and 10 after initial infection. The clinical, microbiological and pathological findings were identical to those seen in field incidents of bovine pneumonic pasteurellosis involving recently housed, weaned, single-suckled calves.

Animals↗

PubMed1991

Changes in blood and bronchoalveolar lavage fluid components in calves with experimentally induced pneumonic pasteurellosis.

Pneumonic pasteurellosis was experimentally induced in calves by inoculation of 5 x 10(8) Pasteurella haemolytica organisms into the right diaphragmatic lung lobe. Blood and bronchoalveolar lavage fluid samples were obtained prior to inoculation and at postinoculation hour (PIH) 2, 4, and 6. Calves developed acute lung injury, characteristic of pneumonic pasteurellosis. Lesions were found only in the right diaphragmatic lobe. By PIH 4, significant (P less than 0.01) increases were detected in lavage fluid total cell count, neutrophil count, total protein and albumin concentrations, and alkaline phosphatase (ALP) and lactic dehydrogenase (LD) activities. Myeloperoxidase and elastase activities did not increase. Neutrophil depletion ameliorated the lung lesions and prevented the increase in lavage fluid cell count, total protein, and albumin concentrations and ALP and LD activities. Treatment with the iron chelator, deferoxamine mesylatehydroxyethyl starch, attenuated the increase in total protein and albumin concentrations and ALP and LD activities at PID 4, but not PIH 6. Treatment with a neutrophil function inhibitor, pentoxifylline, prevented the increase in lavage fluid neutrophil numbers, but accentuated the increase in total protein and albumin concentrations, and ALP, LD, myeloperoxidase, and elastase activities.

Animals↗

PubMed2000

The potential role of the Arthus and Shwartzman reactions in the pathogenesis of pneumonic pasteurellosis.

Pneumonic pasteurellosis (PP) is an economically important disease in cattle, sheep, and goats. Pasteurella haemolytica is commonly isolated from the severe fibrinopurulent pneumonia that characterize this respiratory syndrome. During infection, the bacteria produce leukotoxin (LKT) and lipopolysaccharide (LPS), both potent inducers of inflammation. Nonetheless, it has also been demonstrated that an exacerbated host's inflammatory response is responsible for the severe lung damage. Despite research in this field, the pathogenesis of PP is still incomplete. Two classical models of acute inflammatory response induced in laboratory animals, the Arthus and Shwartzman reactions, could explain the pathogenesis of the severe lung lesions that characterize PP.

Animals↗

PubMed2002

Role of Mannheimia haemolytica leukotoxin in the pathogenesis of bovine pneumonic pasteurellosis.

Bovine pneumonic pasteurellosis continues to be a major respiratory disease in feedlot cattle despite the recent advances in our understanding of the underlying complexities of causation. The etiological agent, Mannheimia haemolytica, possesses several virulence factors, including capsule, outer membrane proteins, adhesins, neuraminidase, endotoxin and exotoxic leukotoxin. Accumulating scientific evidence implicates leukotoxin as the primary factor contributing to clinical presentation and lung injury associated with this disease. Unlike other virulence factors, leukotoxin shows cell-type- and species-specific effects on bovine leukocytes. Recent investigations have delineated the mechanisms underlying the target-cell-specificity of leukotoxin and how this contributes to the pathogenesis of lung damage. This review summarizes current understanding of the secretion, regulation, mechanisms of action and evolutionary diversity of leukotoxin of M. haemolytica. Understanding the precise molecular mechanisms of leukotoxin is critical for the development of more effective prophylactic and therapeutic strategies to control this complex disease.

Animals↗

PubMed2003

Association of LPS chemotype of Mannheimia (Pasteurella) haemolytica A1 with disease virulence in a model of ovine pneumonic pasteurellosis.

Host responses during pneumonic pasteurellosis were compared in sheep infected with strains of Mannheimia (Pasteurella) haemolytica A1 differing in their O-antigen type. Nine-week-old, specific pathogen-free lambs were infected intratracheally with parainfluenza type 3 virus (10(8) TCID(50)) followed 7 days later by 5-6 x 10(7) CFU of M. haemolytica A1 possessing rough (group R, 6 lambs) or smooth (group S, 6 lambs) lipopolysaccharide, or saline (group C, 4 lambs). Group C lambs remained afebrile with no evidence of endotoxaemia or bacteraemia and biochemical parameters were normal. Group R and group S lambs became febrile within 2-3 h postinfection and the response was higher and more prolonged in group R lambs. Four group R and 2 group S lambs developed clinical pneumonic pasteurellosis within 24-48 h and the severity of disease correlated with episodes of endotoxaemia, bacteraemia and elevated eicosanoid concentrations. At post-mortem, M. haemolytica (10(7)-10(9) CFU/g) was isolated from the lungs of all 6 group R lambs but from only 1 group S lamb. The results indicate an association between the incidence and severity of ovine pneumonic pasteurellosis and LPS chemotype and suggest an important role for LPS chemotype in determining host-species susceptibility to lung infection.

Animals↗

PubMed1990

A guinea pig model of bovine pneumonic pasteurellosis.

The induction of pneumonic pasteurellosis in guinea pigs (Cavia porcellus) was examined. Specific pathogen free male guinea pigs were anesthetized and a tracheostomy performed to introduce 10(5), 10(4) or 10(3) Pasteurella haemolytica-A1 into the left principal bronchus. The surgical site was closed with tissue adhesive and staples and the animals were monitored for signs of respiratory tract infection. Within 24 hours after inoculation they became depressed, anorectic, pyretic and dyspneic. Fibrinous pleuropneumonia with prominent areas of necrosis and hemorrhage was present. Pericardial effusion was a frequent finding. There was infiltration of the pleura and alveoli with degenerate heterophils and macrophages, a hyperplastic mesothelium and fibrin exudation on the pleura and within alveoli. Hemorrhage, congestion, consolidation, edema and fibrin exudation were prominent in the hilar region of the lungs. Bacterial colonies were evident in all airways. More bacteria were recovered from infected lungs than were inoculated (p less than 0.05) indicating P. haemolytica was actively multiplying in the lungs. Hematological and clinical chemistry data were consistent with fibrinous pneumonia, however, blood cultures were positive for P. haemolytica in 61% (11/18) of animals sampled. Examination of pneumonic pasteurellosis in guinea pigs may be useful in studying pathogenetic and pathological features applicable to bovine pneumonic pasteurellosis (shipping fever pneumonia).

Animals↗

PubMed1998

Expression of the neutrophil chemoattractant interleukin-8 in the lesions of bovine pneumonic pasteurellosis.

We investigated the expression of interleukin-8 (IL-8) in pneumonic pasteurellosis of cattle because neutrophils are important mediators of tissue injury in this disease and because IL-8 is a major neutrophil chemoattractant in other species. We also compared IL-8 expression in bacterial and viral pneumonia, since the latter lacks the severe neutrophil exudation typical of pneumonic pasteurellosis. IL-8 expression was assessed by northern analysis, in situ hybridization, enzyme-linked immunosorbent assay, and in vivo bioassay. IL-8 mRNA expression was elevated dramatically in lesions of pneumonic pasteurellosis compared to unaffected lung from the same calves. In situ hybridization revealed intense expression of IL-8 mRNA in alveolar macrophages and neutrophils and milder expression in bronchiolar and alveolar epithelium, interstitial cells, and pleural mesothelium. Bronchoalveolar lavage fluid from lesional lung contained 16.06+/-4.00 ng/ml IL-8, whereas those from nonlesional and normal lung contained 0.34+/-0.11 and 0.01+/-0.002 ng/ml, respectively. We detected IL-8 expression at only minimal levels in bovine respiratory syncytial viral pneumonia. Lung extracts from lesions of pneumonic pasteurellosis induced vigorous neutrophil infiltration following injection into bovine skin, and 89% depletion of IL-8 from the extract reduced this neutrophil influx by 60%. These results demonstrate consistent upregulation of IL-8 expression in lesions of pneumonic pasteurellosis, implying a role for IL-8 in the ongoing recruitment of neutrophils to established lesions of pneumonic pasteurellosis. Because neutrophil-mediated tissue injury is critical to the pathogenesis of pneumonic pasteurellosis, these data suggest that neutralization of IL-8 activity could ameliorate the severe clinical signs and lesions of this disease.

Animals↗

PubMed1989

The evolution of vaccines for bovine pneumonic pasteurellosis.

Since the early 1900s bovine pneumonic pasteurellosis has been recognised as a major economic problem to European and North American cattle industries. Initial attempts to prevent the disease were complicated by incomplete knowledge of the causative organisms. Despite some early reports of vaccine-induced protection against disease, initial vaccines were of questionable protective value. From the late 1950s to the 1970s Pasteurella haemolytica and P multocida bacterins were the primary type of vaccine used commercially and experimentally. When viruses, most notably bovine herpesvirus 1 (infectious bovine rhinotracheitis virus) and parainfluenza-3 virus, were found to be associated with bovine respiratory disease, viral vaccines were used in attempts to prevent pneumonic pasteurellosis. Combinations of bacterins and viral vaccines were also developed and evaluated. Collectively, bacterins, viral vaccines and bacterin-virus combinations did not consistently reduce disease in experimental trials or field use. By the 1980s some studies using live vaccines were reportedly successful in reducing the incidence of pneumonic pasteurellosis. Current experimental studies revolve around the identification and incorporation of specific Pasteurella species antigen extracts into vaccines. The efficacy of these new extract vaccines is yet to be determined.

Animals↗

PubMed1995

Increased tumor necrosis factor-alpha and interleukin-1 beta expression in the lungs of calves with experimental pneumonic pasteurellosis.

We used a well characterized pneumonic pasteurellosis model in calves to determine whether increased proinflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) expression and secretion were associated with pneumonic lesions. Bronchoalveolar lavage fluids, lavage cells consisting of alveolar macrophages and neutrophils with degenerative changes, and lung tissues were analyzed for the presence of TNF-alpha and IL-1 beta approximately 48 h following endobronchial inoculation of logarithmic phase Pasteurella haemolytica 12296 organisms. Levels of TNF-alpha and IL-1 beta mRNA were significantly increased in lavage cells of P. haemolytica-infected animals but not in cells from phosphate buffered saline (PBS) inoculated controls based on in situ hybridization analysis. Significantly increased levels of TNF-alpha, and IL-1 beta mRNA were also expressed within the pneumonic lesions from P. haemolytica-infected calves. In contrast, lung tissues from PBS-inoculated control calves had cytokine mRNAs expressed at extremely low levels. Increased levels of bioactive IL-1 and immunoreactive (not bioactive) TNF-alpha were found in lavage fluids from P. haemolytica-infected calves compared with lavage fluids from PBS-inoculated calves. These findings indicate that the proinflammatory cytokines TNF-alpha and IL-1, may be associated with pathogenesis of lung injury in bovine pneumonic pasteurellosis.

Animals↗

PubMed1996

The goat as a model for studies of pneumonic pasteurellosis caused by Pasteurella multocida.

A model of pneumonic pasteurellosis has been established in goats using Pasteurella multocida harvested from pneumonic lungs of goats (types A and D), rabbits (type A) and sheep (type D). The resultant infections were acute, subacute or chronic. The gross and histological lesions of the subacute and chronic infections were typical of pneumonic pasteurellosis. P. multocida type D produced significantly (P < 0.01) more severe lesions when compared with other isolates. There were strong correlations between the clinical signs and the severity of lesions.

Acute Disease↗

PubMed1995

A field evaluation of the efficacy of two vaccines against ovine pneumonic pasteurellosis.

Two vaccines against pneumonic pasteurellosis were evaluated for efficacy in lambs transported by sea from New Zealand to Saudi Arabia. One vaccine contained whole cell antigens of Pasteurella haemolytica A2 grown under iron restricted conditions. The other contained Pasteurella haemolytica A1 cell surface and leucotoxin antigens. There was no clear evidence of either vaccine leading to a lower pneumonia death or lesion rate than for the control group.

Journal Article↗

PubMed1992

Use of an indwelling bronchial catheter model of bovine pneumonic pasteurellosis for evaluation of therapeutic efficacy of various compounds.

A model of bovine pneumonic pasteurellosis, using an indwelling bronchial catheter for inoculation and subsequent lavage of a single main stem bronchus of the lung, was evaluated in a preliminary efficacy trial of an experimental therapeutic compound. Inoculation of 10(7) Pasteurella haemolytica organisms into the bronchus consistently induced a focal pneumonic lesion with typical morphology of pneumonic pasteurellosis in the left or right caudal lung lobe. The experimental treatment caused significant (P less than 0.05) reduction in lung lesion volume, compared with that of a saline-treated control. It also caused significant (P less than 0.05) reduction in lavage fluid bacterial counts at 48 hours after inoculation, compared with counts in the controls. The inflammatory cell count and the percentage of neutrophils increased markedly in lavage fluids 8 hours after inoculation, but differences were not detected between treatments. Significant differences between treatments were not found in clinical signs, rectal temperature, or histologic changes. This model appears to be a sensitive indicator of treatment efficacy and has the advantage over previous models of pneumonic pasteurellosis of allowing sequential monitoring of the primary lesion site.

Animals↗

PubMed1986

Induction of immunity against pneumonic pasteurellosis following experimental infection in calves.

Immunity against pneumonic pasteurellosis was studied in calves after recovery from experimental respiratory disease with Pasteurella haemolytica. Nine calves were exposed to aerosols of parainfluenza-3 virus and Pasteurella haemolytica A1 six days apart to produce respiratory disease. After recovery from the disease, these nine principal and four control calves were challenged with aerosols of bovine herpesvirus 1 and P. haemolytica A1 four days apart. With this viral-bacterial challenge, the nine principal animals failed to develop clinical responses to this bacterial challenge and their lungs did not show the growth of P. haemolytica on cultures, whereas two of four control calves had elevated temperatures and developed necropurulent pneumonia with the isolation of P. haemolytica from the lungs. The principal calves had developed high levels of cytotoxin neutralizing antibodies in their sera following parainfluenza-3 virus-P. haemolytica infection. This demonstrated that immunity against pneumonic pasteurellosis can be achieved, with a suggestion that further search for an effective vaccine for P. haemolytica is warranted.

Aerosols↗

PubMed2001

The importance of interleukin-8 as a neutrophil chemoattractant in the lungs of cattle with pneumonic pasteurellosis.

Interleukin-8 (IL-8), an in vitro and in vivo neutrophil chemoattractant, is expressed at high levels in the lesions observed in bovine pneumonic pasteurellosis. Because of the role of neutrophils in the pathogenesis of pneumonic pasteurellosis, we investigated the relative importance of IL-8 as a neutrophil chemoattractant in this disease. Bronchoalveolar lavage (BAL) fluid was harvested from calves experimentally infected with bovine herpesvirus-1 and challenged with Mannheimia haemolytica. Neutrophil chemotactic activity was measured in pneumonic BAL fluid samples treated with a neutralizing monoclonal antibody to ovine IL-8, and compared to the activity in samples treated with an isotype-matched control antibody. Bronchoalveolar lavage fluid was analyzed at a dilution which induced a half-maximal response, and the concentrations of antibody were optimized in a preliminary experiment. Following incubation of replicate samples of diluted pneumonic bovine BAL fluid with 70 microg/mL of IL-8-neutralizing antibody or control antibody, the neutrophil chemotactic activities of the samples were determined using an in vitro microchemotaxis assay. Overall, pretreatment of BAL fluid samples with neutralizing anti-IL-8 antibody reduced neutrophil chemotactic activity by 15% to 60%, compared to pretreatment with control antibody. This effect was highly significant (P < 0.001), and was present in 5 of 5 samples. These data indicate that IL-8 is an important neutrophil chemoattractant in calves with pneumonic pasteurellosis, but that mediators with actions redundant to those of IL-8 must also be present in the lesions.

Animals↗

PubMed1984

Bovine pneumonic pasteurellosis: effect of vaccination with live Pasteurella species.

Experimental bovine pneumonic pasteurellosis was induced in beef calves by a transthoracic challenge exposure with Pasteurella haemolytica serotype 1 or P multocida type 3. Challenge exposure lesions were quantified by a lesion scoring system based on size and extension of lesions with larger scores assigned to the more severe lesions. Calves inoculated with live Pasteurella sp by aerosol or parenteral routes developed high serum antibody titers to the homologous organism, as determined by a quantitative fluorometric procedure. Mean lesion scores were approximately 2 to 20 times higher in control than those in vaccinated calves. There was a significant correlation (P less than 0.05) between high serum antibody titers at the time of challenge exposure and a low lesion score in 4 of 6 experiments.

Aerosols↗

PubMed1998

The clinical efficacy of enrofloxacin in the treatment of experimental bovine pneumonic pasteurellosis.

The clinical efficacy of enrofloxacin was tested in calves with experimentally induced pneumonic pasteurellosis. A strain of Pasteurella haemolytica, biotype A, serotype 1 (P. haemolytica A1), which had been isolated from an outbreak of pneumonic pasteurellosis in feedlot calves, was used to induce the disease in 24 eight-month-old calves. Each animal received, by intratracheal injection, 6 x 10(11) colony forming units of P. haemolytica A1 in a four-hour log phase culture. Twelve similar animals were kept as non-infected controls (Negative Control group). Treatment of the infected animals commenced 40 h after infection and was as follows: 12 animals each received 2.5 mg/kg enrofloxacin subcutaneously and 12 animals each received 5 ml sterile saline intramuscularly (Positive Control group). All treatments were given once daily for three consecutive days. Clinical examinations were performed on all animals once daily, starting prior to infection and continuing until 12 d post-infection. The parameters evaluated were rectal temperature, habitus (attitude), ocular mucous membrane congestion and abnormal sounds on lung auscultation. On day 14 post-infection, all animals were killed and their lung lesions (if any) estimated as the percentage involvement of each pair of lungs. The only statistically significant (P > or = 0.05) differences observed were between the Negative Control group and the Positive Control group. Noticeable differences were seen between the enrofloxacin-treated group and the Positive Control group, but they were not statistically significant (P > 0.05). The average lung lesion score (pneumonic lesions as a percentage of total lung volume) for the Positive Control group was 12.1% and that of the enrofloxacin-treated group, 8.4%. This difference was not statistically significant (P > 0.05).

Animals↗

PubMed1999

Evaluation of structural and functional alterations of circulating neutrophils in calves with experimentally induced pneumonic pasteurellosis.

OBJECTIVES: To determine the structural and functional alterations in circulating neutrophils that may lead to sequestration in lung microvasculature and endothelial injury in calves with experimentally induced pneumonic pasteurellosis. ANIMALS: 10 healthy, 2- to 4-week-old male Holstein calves. PROCEDURES: Holstein calves were anesthetized and inoculated intrabronchially with Dulbecco phosphate buffered saline (0.9% NaCl) solution (DPBSS; 5 control calves) or 1 x 10(9) Pasteurella haemolytica organisms (5 infected calves). Blood samples were collected before and 1, 2, 4, and 6 hours after inoculation. Total and differential WBC count, dilute whole blood leukocyte deformability, neutrophil size distribution, and neutrophil surface CD11b expression were measured in blood samples. RESULTS: A progressive decrease in leukocyte deformability and increase in neutrophil size was detected 1, 2, 4, and 6 hours after inoculation of P haemolytica. Neutrophil surface CD11b expression was greater than baseline values at 6 hours after inoculation of P haemolytica. Two populations of neutrophils with an increase in size were detected in P haemolytica-infected calves. Both subpopulations had increased CD11b expression, compared with neutrophils that were typical in size. CONCLUSIONS AND CLINICAL RELEVANCE: Neutrophils circulate in an activated and nondeformable state in calves with experimentally induced pneumonic pasteurellosis. A decrease in neutrophil deformability and neutrophil aggregation may contribute to neutrophil trapping in the lung microvasculature during pneumonic pasteurellosis in calves.

Animals↗

PubMed1997

Role of tissue factor in intra-alveolar fibrin deposition and coagulopathy associated with pneumonic pasteurellosis in cattle.

OBJECTIVE: To determine the role of tissue factor (TF) in the coagulation events leading to intra-alveolar fibrin deposition and intravascular thrombosis associated with pneumonic pasteurellosis in cattle. ANIMALS: Healthy 2- to 4-week-old male Holstein calves. PROCEDURES: Blood and bronchoalveolar lavage samples were collected before and at 1, 2, 4, and 6 hours after inoculation of saline solution or Pasteurella haemolytica. Total leukocyte count, platelet count, plasma total protein concentration, prothrombin time, and partial thromboplastin time were measured in blood samples. Total nucleated cell count, total protein concentration, and procoagulant activity were measured in bronchoalveolar lavage samples. Additionally, platelet survival in blood platelet accumulation in affected lung tissue, and gross and microscopic lung lesions were determined. RESULTS: Administration of TF monoclonal antibodies (MAB) TF1-1F7 prevented the decrease in platelet survival and the increase in bronchoalveolar lavage fluid TF-dependent procoagulant activity observed in calves not treated with MAB TF1-1F7 antibody, but did not attenuate the increase in lavage fluid neutrophil numbers and total protein concentration, MAB TF1-1F7 administration reduced the percentage of lung affected by pneumonic lesions from 51.81% to 10.40% and attenuated intra-alveolar deposition of fibrin, neutrophils, and erythrocytes. CONCLUSION: Intra-alveolar fibrin deposition and activation of coagulation in cattle with pneumonic pasteurellosis is, at least in part, mediated by TF. CLINICAL RELEVANCE: Treatments that neutralize TF activity may attenuate lung injury in cattle with pneumonic pasteurellosis.

Animals↗