The role of mycoplasmas, especially ureaplasmas, in the
urogenital tract of sheep was investigated both by survey and
by pathogenicity experiments in vitro and in vivo.
The survey revealed that Ureaplasma are the most frequently
isolated species from the ovine urogenital tract, and demonstrated
an association between the occurrence of vulvovaginitis and the
presence of ureaplasmas. M.capricolum and A.axanthum, two species
not previously reported in the United Kingdom, were among the
other seven species isolated.
Differences in virulence of the strains of ureaplasma
isolated from sheep were investigated using both in vitro and
in vivo systems. The in vitro systems used were cell and organ
cultures as well as embryonated hens' eggs, but although none
of these gave successful results, a cytopathic effect observed
in ovine uterus cell cultures did suggest that these organisms
are potentially pathogenic. The various in vivo systems
investigated included inoculation of several animal species
by a variety of routes. The production of mastitis in lactating
mice after intramammary inoculation confirmed the pathogenicity
seen in cell cultures but possible variations in virulence
between strains were not identified by this model. However,
the strains varied in their ability to induce mastitis in the
lactating bovine udder, suggesting that variations in
virulence do occur but are revealed only by in vivo systems.
Transmission experiments in sheep were carried out and
demonstrated that inoculation of these organisms per vaginam
resulted in vulvitis. They showed also the importance of
venereal transmission in the spread of the organisms to
previously unmated ewes, some of which developed vulvitis.
Ureaplasmas could be consistently recovered from all animals
which developed the disease. The vulvitis did not affect
conception rates or the reproductive efficiency of the ewes.
Two serological tests (metabolism-inhibition and indirect
immunofluorescence) demonstrated that at least three groups
of ovine ureaplasmas occur in the United Kingdom. All 106
strains examined in this study could be assigned to one of the
three groups, using antisera prepared in specific pathogen-free
lambs ,against a representative of each group.