Late Term Abortion

The last trimester is getting close. Even though that foal is near to the ground, danger still lurks around the barn. Late-term abortion may occur as a result of equine herpes (rhino), placentitis, premature placental separation, and placental insufficiency.

Equine Herpes virus-1 (Rhinopneumonitis): Signs you may see which can signal an impending abortion include changes in the abdominal contours, early udder development or even lactation, vaginal discharge, and the most devastating of all, either the fetus itself or shreds of placenta hanging from the vulva. Equine Herpesvirus-1 (Rhinopneumonitis): Listed as the second cause (6-15%) of abortion in mares, vaccination may reduce the incidence. The mare may be exposed as close as 2 weeks or as far away as 16 weeks to the virus. Abortion is usually seen between the 7-10th month of gestation. No warning is given to abortion. There are several vaccines on the market for equine herpes. Vaccination should begin prior to the pregnancy. Routine vaccination schedule includes inoculation with a modified live vaccine at least 3-4 weeks before breeding followed by use of a killed product at 5,7, and 9 months of gestation. Note that even with the most stringent vaccination schedule all abortions due to herpes virus won't be avoided.

Placentitis: This is the most common cause (30%) of abortion in the mare. Infection of the placenta can be caused by either bacteria or fungi. Infection can be the result from the bloodstream (hematogenous) or as a result of an ascending infection through the cervix. Infection through the cervix is more common. Two surgical procedures which can reduce the incidence are 1) Caslick's operation (suture down the vulva) and 2) Urethral extension (brings the urethral opening closer to the vulvar lips). For mares in which poor cervical tone is diagnosed, progesterone may be administered.

Potomac Horse Fever (PHF): Although the frequency of naturally occurring abortion due to PHF is unknown, Ehrlichia risticii , the organism causing PHF, has clearly been established as a cause of equine abortion. Classically PHF is known as a diarrheal disease. Fever, depression, anorexia, colic, and laminitis are other features seen in the horse. Following recovery from PHF, pregnant mares may abort. Abortion is accompanied by placentitis and retained placenta in most cases. There are three vaccines available for the prevention of PHF, however the effect of vaccination on the occurrence of abortion is unknown at this time.

Premature placental separation : Placentitis, uterine hemorrhage seen coming from the vulva to no signs of impending abortion are the variety of signs seen with this condition. Typically you see discreet pale areas on the placenta. Treatment of the underlying cause may help the mare continue the pregnancy. Some advocate the use of progesterone.

Placentitis: Premature lactation or udder development are consistent signs of placentitis. This condition is more often seen in the aged broodmare which have had several foals. Age and multiple births result in decreased uterine tone and increased incidence of uterine scarring or uterine cyst formation. Systemic antibiotics and progesterone are among the various therapies used in the prevention of abortion due to placentitis. A thorough breeding soundness examination on the mare are important in the identification and treatment of mares which may be predisposed to this condition.

Equine Viral Arteritis (EVA): Another viral disease of the horse which may cause abortion. The signs seen with this disease vary from horse to horse, as all diseases may. High fevers, snotty nose, limb swelling (edema) or ventral edema (abdomen/thorax) are signs caused by this disease. A killed vaccine is available for the prevention of EVA. This virus can be shed in the semen of infected stallions, therefore avoid breeding to those stallion recently diagnosed with this disease.

Twinning: Likely the most common cause of NONINFECTIOUS abortion. As in placentitis, you may see premature lactation and udder development. Use of ultrasound in the detection of twins in the early stages of pregnancy is essential. Ultrasound may detect pregnancy in the mare as early as 15 days post ovulation. A +90% success rate for pinching one twin and retaining the pregnancy can be achieved by an experienced veterinarian.

Colic: In cases of severe colic, the mare usually aborts within 7 days. There are many signs of colic most of which you are aware. Pawing, kicking, biting the flank, sweating, getting up and down, straining are but a few of the signs a horse with colic may exhibit. Colic is a disease which plagues the horse. Regular deworming and consistent feeding and watering are essential in minimizing the horse's chances of having colic.

Awareness of potential problems is one of the keys to prevention. If your mare has had any of these diseases obviously the potential for abortion exists. When dealing with mares considered to be a high risk for abortion, good care, a watchful eye, and plain common sense will get you and your mare through the tough times.