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.