Evidence that blood-borne infection is involved in the pathogenesis of bovine pneumonic pasteurellosis

Five calves were inoculated intravenously with 10(8) colony forming units (cfu) of Pasteurella haemolytica A1; the mean score for pneumonic consolidation 3 days post-inoculation was 28%, and the mean clinical score was 7.8. Five calves inoculated intratracheally with 10(9) cfu of the same strain of P. haemolytica had comparable scores (34% and 8.8). Histological lesions of fibrinous pneumonia were similar in all calves. P. haemolytica was recovered from all but one of the affected lungs. From one calf killed in extremis 3 hours after intravenous inoculation, numbers of bacteria recovered from lung were 1,000-fold greater than from liver and spleen. A similar difference in bacterial numbers was also obtained from a gnotobiotic calf killed in extremis, 12 hours after intravenous inoculation of 10(8) cfu P. haemolytica. Evidence from these experiments supports the hypothesis that the blood-borne route is important in the pathogenesis of bovine pneumonic pasteurellosis.

Increased severity of calf pneumonia associated with the appearance of Mycoplasma bovis in a rearing herd

An increase in deaths in calves from respiratory disease from an average of 9.7 per year to 36.5 per year corresponded with the isolation of Mycoplasma bovis from the lungs. It is suggested that this mycoplasma enhanced the severity of the disease which was normally present on the farm. The characteristic microscopic lesion and demonstration of M bovis by immunoperoxidase labelling could be useful aids to diagnosis.

Production and characterization of bovine monoclonal antibodies to respiratory syncytial virus

Six interspecific hybridomas (heterohybridomas) secreting bovine monoclonal antibodies (MAbs) against respiratory syncytial (RS) virus were produced. Four of the heterohybridomas were formed using the mouse myeloma cell line NS1 as the fusion partner, one using NS0, and the remaining heterohybridoma was formed using a bovine X murine hybridoma as the fusion partner. Five heterohybridomas secreted bovine IgG1 and one secreted IgG2. All six MAbs recognized human subtype A and B viruses as well as bovine RS virus. They were specific for the fusion glycoprotein and reacted with a 140K dimer and a 70K monomer in a Western blot of native antigen; three also bound to the 46K F1 component and its 22K cleavage product in a blot of reduced antigen. Two of these MAbs neutralized RS virus infectivity, inhibited virus-induced fusion, lysed RS virus-infected cells in the presence of complement and protected mice against RS virus challenge.

Immune response of cattle to respiratory mycoplasmas

M. bovis and M. dispar produce very different types of response in the calf lung. The immune response of the host plays a major role in the formation of the lesion induced by M. bovis and this response is predominantly Ig mediated. In contrast M. dispar produces a much milder reaction in the lung which may be related to an ability of the mycoplasma to inhibit the host's immune response. Recovery from infection appears to be primarily mediated by IgG present in the lung and functioning in conjunction with alveolar macrophages. The immunity following vaccination which is observed in experimental studies and field trials is also likely to be mediated by the same mechanism.

Protection against respiratory disease in calves induced by vaccines containing respiratory syncytial virus, parainfluenza type 3 virus, Mycoplasma bovis and M dispar

A field trial to assess the ability of two vaccines to protect calves against respiratory disease was carried out on a large beef rearing unit in southern England over the two winters of 1983 to 1984 and 1984 to 1985. A quadrivalent vaccine containing the killed antigens of respiratory syncytial virus, parainfluenza virus type 3, Mycoplasma bovis and M dispar or a vaccine containing only the respiratory syncytial virus component were inoculated into 246 and 245 calves, respectively; 245 calves remained as unvaccinated controls. The calves were reared in seven batches and outbreaks of disease occurred in five; significant protection was achieved in the four batches in which disease was associated with respiratory syncytial virus and M bovis infection, together or independently. The death rate from pneumonia was 9 per cent in the control group, 2 per cent in the calves inoculated with the quadrivalent vaccine (P less than 0.001), a protection rate of 77 per cent, and 3 per cent in the calves inoculated with the respiratory syncytial virus vaccine (P less than 0.01), a protection rate of 68 per cent. The proportion of calves receiving treatment for respiratory disease was 38 per cent in the control group, 25 per cent in the calves inoculated with the quadrivalent vaccine (P less than 0.001) and 27 per cent in the calves inoculated with the respiratory syncytial virus vaccine (P less than 0.01). The results show that protection against respiratory disease can be achieved by parenteral vaccination of calves with the appropriate inactivated microorganisms.

Field trial of a quadrivalent vaccine against calf respiratory disease

A quadrivalent vaccine containing the killed antigens of respiratory syncytial virus, parainfluenza virus type 3, Mycoplasma dispar and M bovis, emulsified with an oil adjuvant, was tested for efficacy against naturally occurring calf respiratory disease. Three batches of beef cattle aged 12, seven and three weeks at the time of first vaccination were used. Within each batch of approximately 100 animals, half were vaccinated subcutaneously on three occasions, three weeks apart and half served as unvaccinated controls. Over the trial period, from November 1981 to May 1982, 27 per cent of the control calves were treated for respiratory disease compared with 16.3 per cent of the vaccinated animals. This reduction of non-fatal disease in the vaccinated animals represented a protection rate of almost 40 per cent and was statistically significant (P less than 0.05). Mortality was also reduced from 3.4 per cent in the control calves to 1.9 per cent in the vaccinated animals but this difference was not statistically significant. During a major outbreak of disease associated with respiratory syncytial virus, the protection rate increased to 69 per cent (P less than 0.01). Furthermore, in the batch of cattle aged seven weeks at first vaccination there was significantly less pneumonic consolidation at death in the vaccinated animals than in the control animals (P less than 0.05).

Lymphocyte transformation response of calves to respiratory syncytial virus

Virus-specific cell-mediated immunity, as determined by in vitro lymphocyte transformation (LT), was demonstrated in calves following infection and vaccination with respiratory syncytial virus (RSV). After experimental infection, 4 of 6 gnotobiotic calves and 6 of 21 conventional calves developed a significant LT response to RSV. By means of a whole blood assay, the LT responses of calves were examined after vaccination with an inactivated vaccine, which consisted of glutaraldehyde-fixed bovine nasal mucosa cells persistently infected with a bovine strain of RSV (GC), a live modified bovine strain of RSV (MV), or a live temperature-sensitive mutant of a human strain of RSV (ts-l). Three weeks after vaccination, a virus-specific LT response was detected in 6 of 6 calves given the GC vaccine, 0 of 4 calves given the MV vaccine, and 2 of 4 calves given the ts-l vaccine. The magnitude of the response was greatest in those animals given the GC vaccine. There was no significant correlation between the magnitude of the LT response and levels of serum neutralising antibody. However, the LT response did correlate with serum antibody measured by the single radial haemolysis test 3 weeks after the first vaccination. LT activity to RSV was associated with T and not B lymphocytes. The development of a virus-specific LT response in calves given an inactivated RSV vaccine was not associated with an increase in respiratory disease following challenge with live virus, but rather was related to increased resistance to RSV infection.

Comparative pathogenicity of Mycoplasma bovis and Mycoplasma dispar for the respiratory tract of calves

Mycoplasma bovis and M. dispar are both important in the etiology of calf respiratory disease, but marked differences are evident in the pathogenesis of disease caused by the two species. Both attach to bovine cells but vary in their invasiveness. M. bovis is capable of invading the lung parenchyma from the airways, while M. dispar predominantly infects the ciliated epithelial cells lining the respiratory tract. M. dispar causes ciliostasis in fetal-bovine tracheal organ cultures, whereas M. bovis does not have the same dramatic effect on ciliary activity. The immunological response of the host contributes to the lesions produced by M. bovis. Both T- and B-lymphocytes accumulate in the lung, which becomes a site for the production of antibody. In contrast, M. dispar produces a mild cellular response in the lungs of calves and may have immunosuppressive properties.

Growth of Mycoplasma bovis in organ cultures of bovine foetal trachea and comparison with Mycoplasma dispar

Inoculation of tracheal organ cultures from bovine foetuses with Mycoplasma bovis resulted in a loss of cellular structure of the lamina propria, followed 20-22 days later by lifting and detachment of overlying epithelium. The effect was associated with large numbers of M. bovis, identified by immunoperoxidase labelling and electromicroscopy, infiltrating between the epithelial cells and amassing in the lamina propria, especially in the region of the basement membrane of the epithelium. Ciliary activity was undiminished for up to 18 days following inoculation and little or no cytopathic effect on the ciliated epithelium was seen in spite of the close proximity of large numbers of organisms. In contrast, M. dispar was restricted to the margin of the ciliated epithelium where, as previously reported, it caused pyknosis, sloughing and flattening of the epithelium with consequent loss of ciliary activity. The cytopathology observed for each mycoplasma bore a close similarity to the behaviour of the two mycoplasmas in vivo and it is suggested that the organ culture system may be a useful and relevant system to elucidate the pathogenic mechanisms for each mycoplasma.

Mycoplasma bovis infection in gnotobiotic calves and combined infection with respiratory syncytial virus

Mycoplasma bovis was inoculated alone or in combination with respiratory syncytial virus into the respiratory tracts of 12 gnotobiotic calves. Clinical signs ranged from transient pyrexia to protracted fever accompanied by severe lower respiratory signs and in one case, arthritis. Pulmonary lesions included foci of coagulative necrosis surrounded by mononuclear cells and suppurative bronchiolitis with varying degrees of lympho-reticular hyperplasia. No enhancement of lesions occurred in the combined infections of M. bovis and respiratory syncytial virus. M. bovis was identified by immunoperoxidase labelling in lesions of necrosis, especially at interfaces between the lesion and mononuclear cells and in bronchiolar exudates. Organisms were also located in necrotic lesions of joint capsules, in tonsillar crypts, and in liver.

Systemic and local immune responses of gnotobiotic calves to respiratory infection with Mycoplasma bovis

Gnotobiotic calves were inoculated by the intratracheal route with Mycoplasma bovis and the specific antibody response in sera and tracheo-bronchial washings examined by radioimmunoassay. In sera an IgM response which reached a peak two weeks post infection was followed by IgG1 and IgG2 antibody responses. Low levels of IgA antibody were detected in sera three and four weeks after infection. The predominant antibody in tracheo-bronchial washings 2 weeks after infection was IgA. Four weeks after infection IgG1 antibody predominated, but IgG2 and IgA antibodies were also present. Cells containing Ig were present in the cellular accumulations around the necrotic zones produced by M. bovis in the lung parenchyma two and four weeks after infection. IgG1 containing cells predominated in these cellular infiltrates. IgG2 producing cells were the next in frequency. It is concluded that the lung lesion caused by M. bovis is partly due to the host's immune response, presumably contributing to the control of the infection, and that the cells infiltrating the lung are a major source of the local and systemic IgG antibody that is detected after infection. IgA staining cells were observed in the submucosa of tissues from nasal cavity and trachea. These cells are probably the source of IgA in tracheo-bronchial washings and sera since IgA-producing cells were not a predominant component of the lesion in the lung parenchyma.

Comparison of the pathogenicity of Mycobacterium paratuberculosis and Mycobacterium spp isolated from the wood pigeon (Columba palumbus-L)

The pathogenicity of 4 strains of mycobacteria isolated from wood pigeons and 2 strains of Mycobacterium paratuberculosis was compared in calves, mice and chickens. Three of the 4 wood pigeon strains and the 2 M. paratuberculosis strains produced clinical Johne's disease in calves. All 6 strains were pathogenic for mice and the 4 wood pigeon strains were pathogenic for chickens. The strains were not agglutinated by antisera to strains of the M. avium complex and all were mycobactin-dependent. It was concluded that the wood pigeon isolates may constitute a distinct group with the pathogenic capability of M. avium in chickens and M. paratuberculosis in calves.

Studies on the relationship between coronaviruses from the intestinal and respiratory tracts of calves

An immunofluorescence test on smears of nasal epithelial cells was used to detect coronavirus infection in the respiratory tract of calves. Thirteen gnotobiotic calves were infected with coronavirus isolates derived from faeces or respiratory material: virus was detected in faeces and nasal swabs from all animals. In 115 calves from a field survey, there was a significant association between coronavirus excretion from both respiratory and enteric routes in calves with diarrhoea. In a further 12 calves, at necropsy, the predilection sites for coronavirus growth were the distal small intestine, large intestine and the epithelia of the nasal cavity and trachea. Antigen was not found in lung tissue by immunofluorescence or immunoperoxidase staining. Infection with enteric coronavirus induced immunity to reinfection and to heterologous challenge with two coronavirus isolates derived from the respiratory tract. Nine coronaviruses were cultivated, cloned and antisera to three were prepared in pigs. There was complete virus neutralisation in tests with homologous sera and significant cross reactions with the eight other isolates which were of intestinal and respiratory origin. Thus, these bovine coronavirus isolates belonged to the same serotype despite the source of virus.

A comparison of three vaccines against respiratory syncytial virus in calves

An inactivated vaccine against respiratory syncytial virus (RSV) was compared with two live vaccines. The inactivated (GC) vaccine consisted of glutaraldehyde-fixed bovine nasal mucosa cells persistently infected with RSV and emulsified with oil adjuvant. The live vaccines were a modified virus (MV) derived from a bovine strain of RSV and a temperature-sensitive mutant (ts-1) derived from a human strain. The GC vaccine was inoculated subcutaneously into 12 calves and the live vaccines intramuscularly into eight calves each. Nine unvaccinated calves acted as controls. The vaccines were administered in two doses 3 weeks apart and all calves were challenged intranasally with 2 X 10(7) p.f.u. of bovine RSV 3 weeks after the second dose. At the time of challenge calves given GC, MV and ts-1 vaccines had mean serum neutralizing antibody titres of 25, 19 and 2 respectively; mean titres of IgG1 antibody by radioimmunoassay were log10 4.5, 1.3 and 2.6 respectively and mean zone areas by single radial haemolysis (SRH) were 107, 27 and 36 mm2 respectively. Eleven of 12 calves given GC vaccine were completely protected against challenge but all control animals and those given the two live vaccines were infected. The mean peak titre of virus in nasal swabs of control calves was 3.0 log10 p.f.u./ml and the mean duration of virus shedding was 6.8 days. Both these parameters were significantly reduced in animals given MV and ts-1 vaccines: mean peak titres were 2.1 and 2.4 log10 p.f.u./ml and mean duration of shedding was 3.4 and 3.3 days respectively. Thus, protection correlated better with RSV antibody detected by radioimmunoassay and SRH than with neutralizing antibody. These results are discussed in relation to the possible mechanism by which protection was mediated.

Infection of gnotobiotic calves with a bovine and human isolate of respiratory syncytial virus. Modification of the response by dexamethasone

A bovine and a human strain of RSV both adapted to bovine cell culture, have been inoculated separately into 13 and 7 gnotobiotic calves respectively by 3 different methods. Both strains infected calves and showed similar growth patterns. Virus was recovered from the nasopharynx between one and 11 days with peak titres between 3 and 8 days following inoculation. With the exception of 4 calves treated with dexamethasone no clinical signs and only minimal macroscopic lesions of the lung were induced, which histologically comprised a mononuclear infiltration of alveolar walls and of the peribronchiolar tissue. The serological response to both strains was similar. Antibody was detected by virus neutralisation or single radial haemolysis from 12 days after inoculation. Specific anti-RSV IgM was detected from 10 days and IgG from 16 days after inoculation. Treatment with dexamethasone (0.5 mgm/Kg daily for 10 days) enhanced lung lesions produced by the bovine strain, prolonged the period of virus shedding and increased peak titres. The specific IgM response was suppressed.

Experimental pneumonia in gnotobiotic calves produced by respiratory syncytial virus

A bovine isolate of respiratory syncytial virus (RSV), when inoculated intranasally into eight gnotobiotic calves produced significant macroscopic lesions of the lung (2-25% consolidation) but failed to produce any clinical signs of disease. The microscopic lesions comprised proliferative and exudative bronchiolitis with accompanying alveolar collapse and infiltration by mononuclear cells of the peribronchiolar tissue and alveolar walls. Virus was recovered from the nasopharynx between days 2 and 11 after infection with peak titres between days 4 and 7. Demonstration of viral antigen by immunofluorescence in nasopharyngeal cells followed a similar detection pattern. Virus was recovered from lung or detected by immunofluorescence in the bronchiolar epithelium up to 11 days following inoculation. A serological response to RSV was demonstrated both by virus neutralization and single radial haemolysis (SRH) tests, in serum of calves from 11 days following inoculation. Specific anti-RSV IgM was detected from 9 days following infection. It is suggested that the close resemblance between the experimental disease in calves and the pathology of acute bronchiolitis in children make cattle a particularly relevant model for the human disease.

Concentration of transunsaturated fatty acids in the adipose body tissue of decedents dying of ischaemic heart disease compared with controls

The constituents of the fat of 136 decedents who had died of ischaemic heart disease are compared with the constituents of the fat from 95 controls who had died from other causes. The cases had a lower concentration of fatty acids (L) characteristic of ruminant animal fat and a higher concentration of total transunsaturated acids (T), but the concentrations of certain higher (C20 and C22 mostly monoenoic) acids (H) were similar. The ratio T/L was higher in the cases, which suggests that the cases may have consumed more hydrogenated fats in life than had the controls. The ratio T/L increased linearly with H within both the case and control specimens, which suggests in view of the similarity in the mean levels of H that the difference in trans contents may be concentrated in the lower (18:1 and 16:1) trans acids.

Concentration of 18:1 and 16:1 transunsaturated fatty acids in the adipose body tissue of decedents dying of ischaemic heart disease compared with controls: analysis by gas liquid chromatography

Proportions of "lower" 16:1 and 18:1 trans acids (TL) and "higher" C20 and C22 trans acids (TH) in samples of depot fat taken at postmortem examination from 136 people who had died of ischaemic heart disease (cases) and from those who had died of unrelated causes (controls) have been determined. Whereas mean percentages of TH are virtually identical for cases and controls, the mean value of TL was significantly higher for the case specimens. Although these lower trans acids are present in small amounts in ruminant-animal fat, they are more characteristic of commercially hydrogenated fats. We conclude, therefore, that the cases consumed on average a higher proportion of those hydrogenated fats rich in 16:1 trans and 18:1 trans acids and a lower proportion of ruminant fat than did the controls.

A search for new microorganisms in calf pneumonia by the inoculation of gnotobiotic calves

In a detailed microbiological and pathological study of eight outbreaks of calf pneumonia, which included the inoculation of respiratory material into 18 gnotobiotic calves, a total of five viruses, four species of mycoplasma and 19 species of bacteria were identified. The only microorganism not previously associated with bovine respiratory disease was a Coronavirus. The experimental disease produced in the majority of the gnotobiotic calves by the intratracheal inoculation of unpassaged respiratory material, closely resembled the natural disease. However statistical analysis of the results could not ascribe the disease seen to a single microorganism or to a particular combination of microorganisms. Assuming therefore that no microorganisms were missed in the study, it was concluded that the microbiological cause of the experimental disease lay amongst the organisms already found and that one or more of three other factors, discussed in the paper, accounted for the experimental disease produced.

Ischaemic heart disease and the proportions of hydrogenated fat and ruminant-animal fat in adipose tissue at post-mortem examination: a case-control study

Fatty acids characteristic of ruminant-animal fat have been found to be present in significantly lower proportions in samples from the depot fat of persons dying of ischaemic heart disease (cases) than in specimens from persons dying of unrelated causes (controls). Although such acids are also present, in lesser amounts, in hydrogenated marine oils, this case-versus-control difference is difficult to explain other than on the basis that controls consumed a higher proportion of ruminant-animal fat in their total dietary fat than did the cases. The proportions of polyunsaturated acids and of certain higher (C20 and C22 mostly mono-enoic) acids in the depot fat of cases and controls are virtually identical. There is also no indication of any difference in degrees of saturation of fats between the case and control specimens.

Diagnosis of respiratory syncytial virus infection in the bovine respiratory tract by immunofluorescence

Direct staining of nasopharyngeal smears with hyperimmune bovine serum raised against respiratory syncytial virus (RSV) and conjugated with fluorescein isothyocyanate was compared with virus isolation from 14 experimentally infected animals. Twenty-four out of 107 specimens examined were positive by the fluorescent antibody (FA) method and 21 out of 107 by virus isolation. Most of the FA positives (81 per cent) were detected after the ninth day of infection whereas 80 per cent of virus isolations were made before this time. Only one false positive (one out of 57 specimens) was detected by the FA method in nine uninfected control animals. Non-specific fluorescence presented some problems when examining nasopharyngeal material. The same conjugate was found to be more useful in detecting RSV antigen in lung tissue of eight experimentally infected animals and 11 out of 22 naturally occurring cases of calf pneumonia from five outbreaks of disease. In three of the outbreaks the diagnosis was confirmed by virus isolation and serology. The dominating histopathological response in both the experimental and the natural disease was an acute bronchiolitis and alveolitis. The finding of RSV antigen in association with these lesions provides further evidence for the role of RSV as a respiratory pathogen of cattle.

Hydrogenated oils and fats: the presence of chemically-modified fatty acids in human adipose tissue

A total of 231 samples of adipose tissue has been analyzed for trans unsaturated acids which arise in large measure via consumption of hydrogenated fat; 136 specimens derived from patients who had died of ischemic heart disease (cases), the remainder being controls. They have also been analyzed by gas-liquid chromatography which gave information regarding the amounts of 1) "higher acids"--C20 plus C22 acids, mainly monoenoic--which derive from hydrogenated marine oils present in high amounts in certain margarines in the United Kingdom, and 2) "lower acids"--14:1 plus odd-numbered and branched chain acids in the C15 to C17 range--which are present in hydrogenated fat in lower amounts than in, say, butter-fat. Values of trans unsaturated acids tend to be higher, and values of lower acids lower for cases than controls, but we cannot at present conclude that these differences are statistically significant. Case versus control levels in respect of higher acids and linoleic acid do not appear to be significantly different.