A study of mycoplasmas of the ovine lung and their relationship to chronic non-progressive pneumonia of sheep in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University
The relationship of mycoplasmas to diseases of the lower respiratory
tract in a variety of animals was reviewed and investigations were
undertaken to determine the role of micro-organisms, with particular
reference to mycoplasmas, in the aetiology of ovine chronic nonprogressive
A survey of the prevalence of mycoplasmas in pneumonic sheep lungs
revealed that Mycoplasma ovipneumoniae was present in 98% of the lungs
tested, whereas Mycoplasma arginini was present in 4%. Ureaplasmas
were not detected in any lungs.
To facilitate further investigations into the significance of
M. arginini in ovine GNP, the in•~vitro growth of the organism was
investigated and its ultrastructure was determined and compared
with that of M. ovipneumoniae. Although ultrastructural
differences between M. arginini and M. ovipneumoniae were found~ these
wouid probably not allow all cells of each of the two species to
be unequivocally identified in thin sections of lung material.
M. ovipneumoniae, M. arginini and parainfluenza type 3 virus were
shown to be sensitive to digitonin when suspended in either conventional laboratory medium, or in lung homogenate. Furthermore,
treatment of pneumonic lung homogenate with 10 mg/cm3 digitonin
destroyed its ability to transmit ovine CNP. Viruses (in particular
PB virus) were not detected in aliquots of the pool of lung homogenate
used to transmit CNP so it is likely that the necessary digitonin
sensitive component is a mycoplasma. Since M. arginini has a consistently
low prevalence in pneumonic lesions, whereas M. ovipneumoniae
is found in the vast majority of such lesions, it was concluded that
M. ovipneumoniae is responsible for initiating primary lesions of the
disease. This however does not imply that M. ovipneumoniae on its
own is capable of causing lesions comparable in severity to the
fully developed "field" cases.
The inactivation of M. ovipneumoniae by formalin, with a view to
making a vaccine, was investigated.