J.K. Clarke

Chronic non-progressive pneumonia of sheep in New Zealand - a review of the role of Mycoplasma ovipneumoniae.

Chronic non-progressive pneumonia (CNP) is a common disease which affects lambs in New Zealand during late summer and autumn. Mycoplasma ovipneumoniae can be recovered from a high proportion of lesions but it is also present in some normal lungs. Bacteria, especially Pasteurella haemolytica, can also be recovered from more than half the lungs of affected animals. Isolates of M. ovipneumoniae are genetically heterogeneous, as demonstrated by examination of their DNA or total cellular proteins, and are serologically heterogeneous as shown by metabolic inhibition tests. The number of strains present in New Zealand is large and several distinguishable strains can be recovered from each affected lung. Mycoplasma ovipneumoniae has pathogenic potential as indicated by its ability to produce hydrogen peroxide, cause ciliostasis and by its possession of a capsule. Chronic non-progressive pneumonia can be transmitted consistently to over 50% of lambs by inoculation of pooled pneumonic lung homogenate and transmission can be suppressed by broad spectrum antibiotics. In contrast, penicillin does not prevent the development of lesions but diminishes their severity. Pooled lung homogenate treated with digitonin, which inactivates mycoplasmas, has failed to transmit CNP. Pure cultures of M. ovipneumoniae produce only mild lesions in some animals, whereas inoculation with pooled lung homogenate (from which no viruses were isolated) containing mixed strains of M. ovipneumoniae and free from bacteria, is more effective in producing lesions. Research work to date suggests that CNP may be initiated by colonisation of the lung by M. ovipneumoniae which causes ciliostasis and elicits an exudate allowing colonisation of the lungs by bacteria especially M. haemolytica and by other strains of M. ovipneumoniae. The immune response to the initial strain of M. ovipneumoniae may inhibit its replication but would be less effective in inhibiting heterologous strains of the organism allowing their sequential replication. Eventually production of a broad immune response to M. ovipneumoniae would lead to its elimination which in turn would facilitate the elimination of other microorganisms and the resolution of lesions. As natural immunity to CNP occurs within the first year, it may be possible to develop an effective and useful vaccine. Such a vaccine may need to include multiple strains of M. ovipneumoniae.

The prevalence of Mycoplasma ovipneumoniae and Mycoplasma arginini in the respiratory tract of sheep.

Abstract Extract In an initial study of mycoplasmas of the respiratory tract of New Zealand sheep a number of strains of mycoplasma were recovered and identified as either M. ovipneumoniae or M. arginini (Clarke et al., 1974). Investigations in Australia have produced evidence that M. ovipneumoniae is associated with a proliferative interstitial pneumonia in Queensland sheep (Sullivan et al., 1973) and for this reason the present survey was undertaken to investigate the prevalence of mycoplasmas in the respiratory tract of sheepin New Zealand.

The experimental transmission of ovine chronic non-progressive pneumonia

Abstract Intranasal inoculation of pneumonic lung homogenate into 20, five-month-old, conventionally reared lambs caused the development of pneumonic lesions in 17 (85%) of them. These lesions were pathologically indistinguishable from natural cases of chronic, non-progressive, ovine pneumonia. In parallel experiments, using a fresh isolate of Mycoplasma ovipneumoniae, 4 of 20 inoculated animals (20%) showed pneumonic lesions. These lesions were relatively mild except for one animal which had a moderate-to-severe pneumonia. Although one of the uninoculated animals also had minimal lesions, the increase in incidence was significant. The lungs of 10 animals in each group were tested for the presence and titre of M. ovipneumoniae. This organism was not recovered from the control group but was detected in all 10 of the animals inoculated with pneumonic lung homogenate, and in 4 of 10 inoculated with M. ovipneumoniae. These results suggest that M. ovipneumoniae can colonise the ovinelung and produce mild pneum...

Isolation and identification of mycoplasmas from the respiratory tract of sheep in New Zealand

Abstract Extract Chronic pneiamonia is one of the most prevalent diseases of sheep in New Zealand and it is generally believed to be of considerable economic importance although its aetiology is uncertain. In an Australian study of ovine pneumonia St. George et al. (1971) described the transmission of this disease using a mycoplasma recovered from sheep lung, and subsequently Carmichael et al. (1972) suggested the name Mycoplasma ovipneumoniae for the organism involved. Although it cannot be assumed that the disease transmitted to Australian sheep is the same as the natural disease in New Zealand sheep, it is, nevertheless, import ant to know if mycoplasmas are commonly present in the respiratory tract of sheep in New Zealand.

The effect of chemotherapeutic agents on the transmission of ovine chronic non-progressive pneumonia

Abstract The effect of several chemotherapeutic agents on the transmission of chronic non-progressive pneumonia to 5- month-old lambs by the intranasal inoculation of pneumonic lung homogenate was investigated during the mid-summer months. Ronidazole, oxytetracycline, tylosin and penicillin suppressed in varying degree the development of lesions and the growth of bacteria and mycoplasmas in the lung. The effect of penicillin was studied in more detail in a second experiment. As expected, it did not prevent Mycoplasma ovipneumoniae from colonising the lung; however, only 1 of 10 animals treated with penicillin (10%)developed moderate gross lesions whereas 7 untreated animals (70%) showed moderate-to-severe lesions at necropsy. Histologically, a focal bronchiolitis with mild subacute pneumonia in surrounding alveoli was seen in four (40%) of the penicillin-treated lambs, whereas the seven untreated lambs with pneumonia showed severe changes characteristic of field cases of the disease. In addition to confir...

The influence of micro-organisms on the severity of lesions in chronic ovine pneumonia.

Summary The degree to which histopathological lesions correlated with the numbers of M. ovipneumoniae and bacteria was studied in sixty 6 to 9 month-old lambs with chronic and subacute pneumonia slaughtered at a local meatworks. Large numbers of M. ovipneumoniae were associated with chronic proliferative changes such as peribronchiolar fibrosis and alveolar interstitial thickening. The combined effect of large numbers of M. ovipneumoniae and bacteria were associated with neutrophilic exudation and epithelial hyperplasia. However, lymphoid hyperplasia and excess mucus production were associated with low bacterial titres. There was no direct correlation between the numbers of M. ovipneumoniae and bacteria present in the pneumonic lungs.

Pasteurella haemolytica serotypes from pneumonic goatlungs

Abstract Extract Madam:– The significance of Pasteurella haemolytica as a pathogen of cattle and sheep is well established. However, less attention has bcen paid to its role as a pathogen of goats and this limited work relates mainly to tropical countries. (2)(3)(4)(5) The lack of information on this topic and the increase in economic importance of goats in New Zealand led us to undertake a preliminary survey to find which of the 15 serotypes of P. haemolytica are commonly isolated from pneumonic goats in this country.

An in vitro study of the replication of Mycoplasma ovipneumoniae

Abstract The growth of a New Zealand strain of M. ovipneumoniae in broth culture at 37°C was examined. In these conditions, the organism had a minimum division time of 1.7 hr and attained a maximum titre of about 2×109 CFU/ml. Growth produced sufficient turbidity, particularly in shaking cultures, to allow this to be correlated with the viable count. The cultures died rapidly following the attainment of maximum titre. Electron microscopic examination revealed a morphology typical of mycoplasmas, except that most organisms measured 400 to 700nm in diameter which is relatively large. The presence of dumb-bell-shaped forms, and the absence of filaments suggest that the organisms divide by binary fission.

Avian reoviruses in New Zealand

Abstract Extract Detection and propagation of viruses of domestic hens in New Zealand has been carried out mainly by using embryonated eggs. Although this technique of viral propagation is the method of choice, for a range of agents, there are advantages in using cell-culture techniques for some viruses that infect domestic hens. The present study was undertaken to find if reoviruses (respiratory enteric orphan) could be recovered from domestic hens, using chick-kidney-cell cultures.

In vitro sensitivity of New Zealand strains of Mycoplasma ovipneumoniae to some antibiotics

Abstract Extract Carmichael et al. (1972) concluded that Mycoplasmal ovipneumoniae plays a role in the development of proliferative interstitial pneumonia in sheep in Australia. The apparent similarity of the Australian disease to the chronic pneumonia which is widespread in New Zealand sheep prompted the investigations by Alley et al. (1975) which showed M. ovipneumoniae is prevalent in the sheep population and is present in a relatively high concentration in the lungs of affected animals. Because of the possible economic significance of the disease, a survey of the sensitivities of 40 isolates of M. ovipneumoniae to antibiotics; was undertaken and the results are reported here. This investigation is confined to in vitro studies and was undertaken to obtain data which may be relevant when choosing antibiotics to test in any subsequent in vivo study.