The experimental transmission of ovine chronic non-progressive pneumonia

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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 pneumonic lesions. However, the much higher frequency with which pneumonic lung homogenate produced severe lesions implies that lung homogenate contains a further agent, or substance, additionally necessary for M. ovipneumoniae to cause the development of lesions comparable in severity with those seen in the natural disease.