The effect of Toxoplasma gondii infection in unvaccinated and iscom-vaccinated pregnant ewes as monitored by plasma levels of 15-ketodihydroprostaglandin F2 alpha, progesterone, and oestrone sulphate.

In order to study the effect of Toxoplasma infection on hormonal levels in pregnant ewes, twenty-eight Scottish Blackface ewes were dosed orally with Toxoplasma gondii oocytes at 91 +/- 1 days of gestation. Fifteen of these ewes were vaccinated with an experimental Toxoplasma iscom vaccine prior to inoculation. Further three ewes were used as non-infected controls. All challenged ewes became infected. Plasma was analysed for the content of 15-ketodihydro-PGF2 alpha, progesterone and oestrone sulphate. The endocrinological changes appeared to reflect the pathological changes in the uterus. Infected animals tended to show an increase in the levels of the prostaglandin metabolite between two and eleven days after challenge, followed by a decrease in progesterone and later also of oestrone sulphate levels. Following the initial phase, the pattern was more variable but related to the outcome of gestation. There was a marked tendency towards more normal endocrinological patterns in the vaccinated animals in comparison to unvaccinated challenged ones.