Experimental Pasteurella multocida pneumonia in calves.

Pasteurella multocida was isolated from the lungs of calves that died on a farm in the south of England. This organism was inoculated experimentally into 13 calves by the intratracheal route: in all but two of the calves mild clinical disease resulted and at necropsy, three or four days later, pneumonic consolidation involving up to 22 per cent of the lung was observed. P multocida was isolated from all but two of the lungs. Of two calves inoculated intravenously with P multocida, one showed mild clinical disease and slight pneumonic consolidation at necropsy and the other remained normal. Control calves inoculated intratracheally and intravenously with sterile broth showed no signs of illness and no pneumonic consolidation. Histologically the lung lesions comprised a fibrinous bronchopneumonia with variable sized areas of coagulative necrosis, extensive deposition of fibrin and massive dilatation and oedema of the interlobular and pleural lymphatics. It is concluded that P multocida should receive more recognition as a primary pathogen.

Effect of a new macrolide antibiotic (tilmicosin) on pneumonia experimentally induced in calves by Mycoplasma bovis and Pasteurella haemolytica.

Two gnotobiotic calves were treated once with tilmicosin (20 mg kg-1) six hours before they were infected by the intratracheal route with Mycoplasma bovis and Pasteurella haemolytica serotype 1. This treatment prevented colonisation of the lungs by P haemolytica and considerably reduced colonisation by M bovis, and the clinical scores and the extent of pneumonic consolidation, compared with two untreated gnotobiotic calves, both of which had to be killed in extremis for humanitarian reasons within 24 hours of infection. In a second experiment, 10 conventionally reared calves were similarly exposed to infection and, at the onset of clinical disease, five were treated once with tilmicosin (20 mg kg-1). Colonisation by P haemolytica and M bovis, the clinical scores and extent of pneumonic consolidation were suppressed or greatly reduced in the treated compared with the untreated calves, one of which had to be killed in extremis two days after infection. It was concluded that tilmicosin had a beneficial effect.

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.

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).

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.

Experimental pneumonia in conventionally reared and gnotobiotic calves by dual infection with Mycoplasma bovis and Pasteurella haemolytica.

Mild clinical disease was produced in conventionally reared calves by the intranasal inoculation of 18-hour cultures of Pasteurella haemolytica simultaneously with Mycoplasma bovis; at necropsy seven days later moderate pneumonic consolidation was observed in two of four calves. Additional intratracheal injection of these organisms did not increase the severity of disease. In contrast, inoculation of six-hour cultures of P haemolytica with M bovis produced more severe disease and more extensive pneumonic consolidation. The most severe disease and greatest degree of pneumonic consolidation was induced by intranasal and intratracheal inoculation of six-hour cultures of P haemolytica one day after the intranasal inoculation of M bovis. Omitting the intranasal injection of P haemolytica reduced the severity and consolidation only slightly. Studies in gnotobiotic calves revealed that more severe disease and more extensive pneumonic consolidation resulted when M bovis was inoculated before P haemolytic rather than vice versa.

Bacteria associated with calf pneumonia and their effect on gnotobiotic calves.

Samples of pneumonic lung tissue from 140 calves with subclinical pneumonia and 65 calves with fatal pneumonia were examined bacteriologically. Sixty-eight (48 per cent) of the lungs from the subclinical cases and 27 (41 per cent) of the lungs from the fatal cases contained bacteria at more than 10(4) colony forming units (cfu) per gram of tissue. Pasteurella haemolytica was associated more with fatal cases than subclinical cases (P less than 0.001). Of the seven species of bacteria inoculated endobronchially into gnotobiotic calves only P haemolytica produced severe respiratory disease, although some strains of P multocida produced a fatal septicaemia.

Immune response of calves following the inoculation of Mycoplasma dispar and Mycoplasma bovis.

A small but significant reduction in the number of Mycoplasma dispar colonising the respiratory tract after intratracheal challenge was observed in gnotobiotic-calves previously inoculated subcutaneously three times with formalin-killed organisms and oil adjuvant. Injection of M. dispar by the intramuscular route, with oil adjuvant, and 2 weeks later by the intratracheal route, without adjuvant, failed to induce immunity to subsequent intratracheal challenge. Following the subcutaneous injection of killed M. dispar, the amount of antibody detected by single radial haemolysis (SRH) increased markedly with increasing age in groups of calves with average ages of 16 to 155 days when first injected. Most calves aged less than 40 days failed to produce an antibody response to a single injection of M. dispar. With M. bovis a smaller difference was observed between antibody levels generated in calves of different ages; also, calves less than 40 days old produced a detectable SRH antibody response following a single injection of killed M. bovis. IgG1 and IgG2 antibody to M. dispar and M. bovis were measured by ELISA. IgG1 appeared before IgG2 antibody and this was particularly pronounced in younger calves. Also, for both mycoplasmas IgG2 antibody levels were lower in younger than older calves. The IgG1 response to M. dispar was compared in three groups of calves with average ages of 16, 55 and 155 days and was greatest in the oldest and least in the youngest animals. In contrast, the IgG1 response to M. bovis varied little in calves of different ages. It therefore appears that the immune response of young calves to M. dispar is impaired or defective.

Some characteristics of mycoplasma virus Hr 1, isolated from and infecting Mycoplasma hyorhinis. Brief report.

Mycoplasma virus Hr 1 is a short tailed bacteriophage with a polyhedral head about 34 nm across and a tail about 14 nm long. It produces plaques on some strains of Mycoplasma hyorhinis.

Some properties of mycoplasma virus Br 1.

Morphologically mycoplasma virus Br 1 is a typical contractile-tailed bacteriophage with a head 77 nm in diameter and a tail 104 nm long. Its type of nucleic acid was not determined. Br 1 was closely associated with its host cell and assays reflected infectious centres. During growth of Br 1 in mycoplasma cultures at multiplicities of infection (MOI) greater than 0.001, there was a lag period: this was up to 23 hours at an MOI of 35. The mean generation time of a mycoplasma culture infected at MOI up to 235 was 2 hours, compared with 1 hour for an uninfected culture. However in these infected cultures there were viable mycoplasmas all of which appeared to be fully susceptible to Br 1 infection and did not seem to be carrying the virus. Br 1 formed plaques on M. bovirhinis but failed to produce plaques on strains of 8 Mycoplasma, 2 Acholeplasma and 4 bacterial species.

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.

Streptobacillus actinoides (Bacillus actinoides): isolation from pneumonic lungs of calves and pathogenicity studies in gnotobiotic calves.

Pneumonic lungs of 56 calves were examined and 12 (21 per cent) of them yielded Streptobacillus moniliformis-like organisms. These organisms resembled those previously described as Bacillus actinoides or Actinobacillus actinoides. After intratracheal inoculation of cultures of two strains of these organisms, pneumonic consolidation developed in five out of six gnotobiotic calves and involved up to 16 per cent of the lung surface. Histological lesions of interstitial pneumonia were observed in the lungs of all six calves. Swellings at the site of the infection followed intradermal and subcutaneous inoculation of cultures of all strains in calves. Mice showed no signs of illness following intraperitoneal injection of three stains. The bacteriological findings suggested that a more appropriate name for these organisms would be Streptobacillus actinoides.

Identification of ureaplasmas from cattle using antisera prepared in gnotobiotic calves.

Antisera were prepared in gnotobiotic calves to three bovine ureaplasma strains which were selected as representatives of the three clusters of serologically similar, but not identical, strains recognized in previous experiments with rabbit antisera. A further 110 isolates from various organ systems of cattle from six countries reacted by the fluorescent antibody technique with at least one of these bovine antisera and it appears that bovine ureaplasmas can be identified and classified by means of three antisera only. It is suggested that the bovine ureaplasmas could be designated as groups A, B or C, these being further subdivided with rabbit antisera. These findings make possible the screening of cattle for antibody to ureaplasmas with just three antigens and also have implications for immunization.

Mycoplasma-induced arthritis in farm animals.

Mycoplasma-induced arthritis in farm animals is rarely diagnosed. When recognized, it is usually associated with mycoplasma infections at other anatomical sites such as the respiratory tract and mammary glands and presumably follows bacteremia. Cases do occur where arthritis appears to be the primary lesion, but this may only reflect a failure to recognize infection at other sites. In cattle, the mycoplasma species causing arthritis are M. bovis, M. mycoides subsp. mycoides, Mycoplasma spp. Group 7 and Mycoplasma spp. serotype L. In sheep and goats, M. capricolum can cause severe polyarthritis, while M. hyorhinis and M. hyosynoviae have been incriminated in arthritis in pigs.

Mycoplasmosis in cattle, sheep and goats.

Nineteen species or subspecies of mycoplasma infect cattle and 17 species or subspecies infect sheep and goats; of these only three are common to both groups of animals. Diseases associated with mycoplasmas are found in the respiratory and urogenital tracts, mammary glands, joints and eyes. Some of these species of mycoplasma are highly pathogenic, causing diseases of major importance, namely, contagious bovine pleuropneumonia, contagious caprine pleuropneumonia and contagious agalactia. This paper, however, will principally consider the roles, if any, of the various other species of mycoplasma in diseases of cattle, sheep and goats.