Careful management of pregnant mares and preparation for parturition is essential to help prevent cases of equine abortion–losses of pregnancy between 150-300 days of gestation. “The incidence of abortion in mares ranges from 5-15%, and this has a severe economic impact on the equine industry,” said Karen Wolfsdorf, DVM, Dipl. ACT, a veterinarian with Hagyard Equine Medical Institute in Lexington, Ky., in a presentation at the 2006 Hagyard Bluegrass Equine Symposium held October 18-21 in Lexington. This impact is not only due to foal loss, but the mare is rendered unproductive for that year, and she has a decreased fertility rate for the next year. This means there is a potential two-year loss in the mare’s production for her owners.

According to Wolfsdorf, although noninfectious causes of abortion are diagnosed twice as frequently as infectious, when an abortion occurs, it is very important that the farm implements isolation protocols immediately. She cautioned several times that it is “better to be safe than sorry.”

When an abortion has occurred on a farm, the first thing Wolfsdof is interested in is the mare’s history–how far along was the mare in her pregnancy? What horses has the mare been in contact with? Is the mare sick? Are a fetus and placenta present? Next, Wolfsdorf performs a physical and reproductive examination. She takes the mare’s temperature, pulse, and respiration, checks her mucous membranes, and evaluates her gastrointestinal motility/feces. Wolfsdorf examines the vulva for tears and bruising, and she inspects the expelled placenta and fetus (if present) to make sure they are intact and to note any gross abnormalities. Finally, she performs a rectal palpation and ultrasound if the fetus or placenta are not present or a vaginal/uterine examination to make sure nothing is amiss inside the mare as a result of the abortion and/or the fetus or the part of the placenta are not retained.

The management of the mare and the environment is essential. Wolfsdorf says to separate the affected mare from other mares in the field to decrease the chances of potential exposure to infectious agents. If the mare aborted in a field, and the field is contaminated, rope off that section of the field. Wolfsdorf cautions not to “remove the exposed mares or mix them with others on the farm until tests for equine herpesvirus, leptospirosis, and equine viral arteritis (EVA) are returned as negative. If the mare aborted in a stall, remove everything in the stall, place her in a pasture by herself, and disinfect the stall