Pregnancy-specific protein B and progesterone in monitoring viability of the embryo in early pregnancy in the cow after experimental infection with Actinomyces pyogenes.

Actinomyces pyogenes can cause embryonic death and abortion during the early stages of pregnancy in cows. Bovine pregnancy-specific protein B (PSPB) is produced in response to a viable embryo and as such it could be a potential marker for embryronic survival. The plasma concentration of PSPB was monitored in cows following an intrauterine infection with A. pyogenes and during the subsequent abortion and recovery from infection. Plasma progesterone concentrations were also monitored, and the results were compared withthose for animals in which abortion had been induced by prostaglandin F2alpha treatment. In abortions induced both by infection and by cloprostenol, the plasma concentration of PSPB fell steadily from the day of treatment, with a half-life of 7 days. In the cloprostenol-induced abortions, progesterone levels fell dramatically to <0.5ng/ml within 24 hours of treatment, while following inoculation with A. pyogenes , progesterone concentration remained elevated for 20 to 40 days and fell to <0.5ng/ml after evacuation of pus from the uterus. Sequential monitoring of PSPB, which identifies embryonic death when a continuing fall in plasma concentration is demonstrated, is a better indicator of embryonic death following bacterial infection with A. pyogenes than plasma progesterone concentration, which falls only when infection is resolved.