R.B. Marshall

the use of a hardjo-pomona vaccine to prevent leptospiruria in cattle exposed to natural challenge with leptospira interrogans serovar hardjo

Abstract The efficacy of the hardjo component of a hardjo-pomona vaccine was evaluated in yearling heifers under conditions of natural challenge in a commercial dairy herd when endemic hardjo infection was present. Eight heifers received 2 doses of vaccine 4 weeks apart and were run with 10 unvaccinated heifers for a period of 56 weeks. Results from the culture of urinesamples showed that the vaccine either prevented leptospiruria to a significant degree (P<0.05) or, if it developed, greatly shortened its duration (P<0.01). Leptospires were cultured on an average of 5 occasions (range 3 to 8) from each of the infected controls and on only one occasion each from 2 of the vaccinates. Fifty one to 56 weeks after commencement of the trial, 9 of the unvaccinated animals were excreting leptospires while none of the vaccinates were leptospiruric at that time. It is concluded that an appropriate vaccination programme could prevent the maintenance of hardjo infection in the herd.

Respiratory disease in foals and the epizootiology of equine herpesvirus type 2 infection

The epizootiology of equine herpesvirus type 2 (EHV-2) infection was investigated in Thoroughbred foals on a stud farm which in previous years had suffered economic loss due to respiratory disease. Sixteen pairs of foals and their dams were selected for this study and all of the foals became infected with EHV-2 by two to four months of age. These animals responded serologically to the virus infection as detected by an enzyme-linked immunosorbent assay (ELISA). EHV-2 infection persisted in these foals for two to six months with constant or intermittent virus recovery. This persistent infection stimulated continuous production of antibodies against EHV-2. As soon as the antibody levels reached their peak at five to six months, the isolation rate of EHV-2 from the nasal cavity of these animals decreased, and eventually by nine months of age virus could no longer be recovered. Respiratory disease was observed in ten of the 16 foals; and two severely affected animals died at two months of age. EHV-2 was isolated from both foals at ante and/or post mortem examination. It is postulated that EHV-2, either as an initiating agent or by means of immnunosuppression, caused the respiratory disease observed in these foals.

Bordetella parapertussis from lambs.

Abstract Extract Madam:—An organism identified as Bordetella parapertussis has been isolated in significant numbers from nasal swabs, bronchial washings and the lungs of 6–10 month old lambs showing signs of pneumonia. It has also been isolated from normal lambs but attempts to recover it from adult sheep have so far been unsuccessful (Table I).

Protection of cattle against natural challenge with Leptospira interrogans serovar hardjo using a hardjo-pomona vaccine.

Abstract The hardjo component of a bivalent hardjo/pomona vaccine prepared from cultures grown in a protein-free medium was tested in calves which experienced a natural challenge about 7 months after vaccination. A significant degree of protection was obtained using either seroconversion or positive urine cultures as in-dicators of infection. Seroconversion occurred in 10/10 non-vaccinates and 2/9 vaccinates (p <0.01), Leptospires of serovar hardjo were isolated from the urine of 6/10 non-vaccinated calves and 0/9 vaccinated animals (p <0.05).

A study of the heterogeneity of isolates of Mycoplasma ovipneumoniae from sheep in New Zealand

To investigate the heterogeneity of Mycoplasma ovipneumoniae, sixty isolates from three sheep on each of twenty farms were examined by restriction endonuclease analysis (REA) and SDS-PAGE. All were found to be different except for three isolates obtained from one farm. The protein and REA patterns of individual isolates were both highly reproducible and remained unchanged following long term passage (approximately 400 generations) in vitro. No plasmids were detected in the twelve strains which were examined and when two isolates were co-cultured in vitro, no genetic interchange, as judged by changes in REA patterns were detected. Since the heterogeneity of M. ovipneumoniae when examined by SDS-PAGE is too great to allow groups to be recognised, it could be advantageous for this purpose if only surface proteins were compared. As a preliminary step to this end we have identified several surface proteins of M. ovipneumoniae and found that some are common to all strains, one surface protein was shared by five of the eight strains examined and another was unique to one strain. This approach has the potential to allow the recognition of grouping of M. ovipneumoniae isolates.

The epidemiological interpretation of serological responses to leptospiral serovars in sheep.

Serum samples were examined for evidence of leptospiral agglutinins from 928 sheep from 45 lines and kidneys from 12 of these lines for evidence of leptospiral infection. All sheep had been submitted for slaughter at meat works in the Manawatu. Serological results were analysed using the results at a minimum serum dilution in the microscopic agglutination test (MAT) of 1:24 and at a minimum dilution of 1:48. It was shown that a minimum dilution of 1:24 resulted in many non-specific or cross-reactions. A minimum dilution of 1:48 was more accurate for detecting the serological prevalence of specific agglutinins to leptospires in ovine sera. Twenty percent of the sheep had titres of 1:48 or greater to hardjo, 3.8% to pomona, 2.6% to tarassovi, 2.3% to copenhageni and 2.7% to ballum. No titres of 1:48 or greater to australis were detected. Serovar hardjo was isolated from the kidneys of three animals in one line. Eighteen months later 291 serum samples and 95 urine samples were collected from live animals on the property from which the three hardjo infected animals originated. No titres to hardjo were detected in the sera of lambs, but a serological prevalence of 44% and 84% to this serovar was demonstrated in the hoggets and ewes respectively. No leptospires were demonstrated in any of the urine samples. These results show that sporadic infection of sheep with hardjo can occur but they also indicate that infection with this serovar is not endemic and that sheep are unlikely to act as maintenance hosts for hardjo in New Zealand.

Comparison of mycoplasma ovipneumoniae isolates using bacterial restriction endonuclease DNA analysis and SDS-PAGE

Sixteen isolates of Mycoplasma ovipneumoniae recovered from the nasal tract or lungs of sheep from different flocks in New Zealand were examined by bacterial restriction endonuclease DNA analysis (BRENDA) using EcoR1 and by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). All isolates gave BRENDA patterns which differed entirely from one another. Following 20 serial passages (corresponding to approximately 67 generations) of an isolate, no change was detected in the BRENDA pattern. When eight isolates were examined by SDS-PAGE most bands were common but, nevertheless, each isolate was unique in the sense that they differed from one another in one or more bands. The marked heterogeneity of patterns observed when strains of M. ovipneumoniae are compared by BRENDA, together with the stability of such patterns over many generations, will enable this approach to be used to study the epidemiology of individual strains of M. ovipneumoniae within a flock.

The role of wild birds and the environment in the epidemiology of Yersiniae in New Zealand.

A survey was carried out to determine the prevalence of Yersiniae in wild passerines in the lower half of the North island of New Zealand over a period of 12 months. Samples of soil, water and foliage were also collected. Out of a total of 1370 avian samples, only two strains of Y. pseudotuberculosis were isolated and a total of 98 strains of environmental yersiniae were identified, including Y. enterocolitica biotype 1a, Y. frederiksenii, Y. kristensenii and Y. intermedia. No strains of Y. pseudotuberculosis were isolated from 1032 non-avian samples collected, which included 100 samples taken from wild mammals. From the non-avian samples, 51 strains of environmental Yersiniae were identified, of which the relative prevalence of Yersinia enterocolitica, biotype 1a, Y. frederiksenii, Y. kristensenii and Y. intermedia was similar to that in the rural passerines. The prevalence of Yersiniae in soil samples was greater in rural areas than in urban areas of the survey region. In both rural and urban passerine populations, the prevalence of Yersiniae was greater in the winter and early summer than at other times of the year.

Seasonal prevalence of thermophilic Campylobacter infections in dairy cattle and a study of infection of sheep

A total of 273 rectal swabs from dairy cows were cultured for Campylobacter jejuni/coli. The isolation rate was 17/72 (24%), 33/106 (31%) and 11/95 (12%) during summer, autumn and winter respectively. Approximately half of the isolates were C. jejuni and the other half C. coli. The isolates recovered from dairy cows were typed by bacterial restriction endonuclease DNA analysis (BRENDA) and compared with those of sheep. Seventeen different BRENDA patterns were produced by the isolates from dairy cows and six from 27 isolates of sheep. Of these 21 different BRENDA patterns only two were common to sheep and cattle.

The isolation of multiple strains of Mycoplasma ovipneumoniae from individual pneumonic sheep lungs

The heterogeneity of Mycoplasma ovipneumoniae isolates from the lungs of sheep with chronic non-progressive pneumonia (CNP) from the same flock raised the possibility that multiple isolates derived from one lung were not all identical. To test this hypothesis, thirty isolates were obtained from each of six pneumonic sheep lungs at slaughter. Four lungs had relatively severe lesions and from each of these, three or four strains of M. ovipneumonia, distinguishable by REA and in most cases by SDS-PAGE, were detected. From the lungs of each of two sheep with mild lesions, two strains of M. ovipneumoniae were detected. Four isolates from one lung were further examined by restriction endonuclease analysis (REA) using many restriction endonucleases. Those which differed with EcoRI also differed when other restriction endonucleases were used. However, partial digests occurred mainly with those restriction endonucleases which recognise cytosine-rich sequences. The presence of multiple strains of one species of microorganism in individual lesions is an unusual concept which may not be limited to one disease or to one host.