Infertility and fetal loss are a significant problem within the equine industry, causing distress to both the owners and the mares. In around 20 percent of cases, the cause of fetal loss is unknown, but researchers are hoping to come up with answers to this problem
Producing a healthy foal
The ways in which mares tolerate the developing fetus is not fully understood, but in humans, primates and mice, a protein called indoleamine 2,3-dioxygenase produced by the pregnant uterus has been shown to be important.
In research, funded by The Horse Trust, aimed to understand more about how pregnancy is maintained in horses and to learn more about how equine herpe virus may trigger fetal loss, it was discovered that maintaining a viable pregnancy is dependent on the ability of the mother's immune system to tolerate the immunologically foreign fetus.
The ways in which mares tolerate the developing fetus is not fully understood, but in humans, primates and mice, a protein called indoleamine 2,3-dioxygenase produced by the pregnant uterus has been shown to be important.
The research team looked for the presence of IDO and the expression of genes coding this protein in archive tissues of equine placentas using immunochemistry and PCR. They found that IDO was expressed in the equine placenta between days 40 and 70 of gestation, correlating with early invasive stages of placental development in the mare.
This finding suggests that expression of IDO in the equine placenta may help prevent immunological rejection of pregnancy, as it does in other animals.
The researchers also performed preliminary investigations into expression of IDO in equine herpes virus-1 (EHV-1) infected mares. A previous study found infection with equine herpes virus to be the cause of equine fetal loss in 6.5 percent of cases in the UK. It is also a distressing cause of fetal loss as abortions commonly occur in last month of pregnancy.
The researchers found strong expression of IDO in multiple uterine blood vessels of an EHV-1 infected mare that had aborted her fetus. This suggests that expression of IDO may be involved in viral abortions, however further research with a larger sample size is needed to determine the importance of this protein in equine herpes viral abortion.