Mycoplasmas and ovine keratoconjunctivitis.

The clinical course of an outbreak of keratoconjunctivitis in housed lambs and their dams was followed. Signs were transient generally and became severe in only a small proportion of lambs. The outbreak became most obvious when the lambs were 46 to 55 days old, when 46.9 per cent were affected. Mycoplasma conjunctivae isolations, confirmed by comparison with the type strain by biochemical and serological reactions, increased to 62.1 per cent of all eyes swabbed, but no correlation could be demonstrated between presence of the organism and clinical status. The reasons for this are discussed. Mycoplasma ovipneumoniae was also recovered from the eyes of a small number of lambs. Instillation of a broth culture of M conjunctivae into the conjunctival sacs of four hoggs produced a transient keratoconjunctivitis similar to that observed in the field, but no effect was observed in animals inoculated intravenously. M conjunctivae may therefore be the aetiological agent of non-follicular infectious ovine keratoconjunctivitis, although further work in gnotobiotic or specific pathogen free lambs is required to establish the fact beyond doubt.

The experimental infection of specific pathogen free lambs with Mycoplasma ovipneumoniae.

Six colostrum-deprived SPF lambs inoculated endobronchially with a second passage broth culture of a Scottish strain of Mycoplasma ovipneumoniae, were killed in batches of two at seven, 14 and 28 days post-inoculation. One lamb from each batch showed macroscopic and microscopic lung lesions similar to but milder than those described for respiratory mycoplasmoses in other species of animals and exhibited minor clinical symptoms. Mycoplasma were recovered from all infected but from no control animals: five infected lambs yielded mycoplasma from lung tissue. Two lambs infected with M ovipneumoniae by endobronchial intubation were placed in contact with six other SPF lambs. M ovipneumoniae was recovered from the upper respiratory tract only of all six contact lambs, but no pathological changes were noted in their lungs. Both donor lambs yielded mycoplasma from lung tissue, but microscopic lesions were detected in only one of them, and these were minimal. No seroconversion due to the infection could be demonstrated in any of the lambs by either the indirect haemagglutination or metabolic inhibition tests.

The comparison and characterisation of glycolytic mycoplasmas isolated from the respiratory tract of sheep.

Nine strains of glycolytic mycoplasmas isolated from the respiratory tract of apparently healthy sheep, pneumonic sheep and sheep with pulmonary adenomatosis (SPA) were compared with a Queensland strain (Y98) of Mycoplasma ovipneumoniae. All strains were very similar in their reactions in 14 biochemical tests and in their sensitivities to optochin, digitonin, sodium polyanethol sulphonate, and 11 antibiotics. Polyacrylamide-gel electrophoresis and serological cross-reactions by the agar-gel double diffusion, metabolic inhibition (MI) and growht-inhibition (GI) tests also showed that all strains could be classified as M. ovipneumoniae. The MI and GI tests, however, showed considerable intraspecific differences among strains, with apparent polarisation of SPA strains and non-SPA strains at opposite ends of the antigenic spectrum. Two representative strains were tested by the MI test against antisera to 39 mycoplasma species or serogroups, with negative results.