Placentitis Causes Late Fetal Loss in HorsesBy Kentucky Equine Research Staff · June 29, 2011
According to figures published by the Rural Industries Research and Development Corporation, between 20% and 30% of bred mares in Australia fail to produce live foals in a particular year, and nearly half of these losses occur in the second half of gestation. Placentitis caused by bacterial or fungal infection of the placenta is a major cause of fetal loss in late-pregnant mares.
Placentitis is usually caused by bacteria or fungi entering through the cervix. There are few clinical signs in the early stages. By the time the condition is well established, delivery of a live foal is likely in fewer than 30% of affected mares, even with aggressive antibiotic therapy. Fetal growth and development can be negatively impacted, and foals that do survive may be premature or ill.
To limit the losses caused by placentitis, it is important to develop ways of detecting and treating the infection in its earliest stages. A recent study was designed to use ultrasonography in documenting the changes that occur as placentitis develops. A second goal was to determine whether treatment based on ultrasonographic findings was successful in improving fetal and neonatal foal health.
Two groups of pregnant mares were used in the study. Mares in the first group had normal breedings and foalings. Mares in the second group had histories of repeated abortions or delivery of a critically ill foal. The mares were examined by ultrasound at four-week intervals. When abnormalities were detected, mares were treated with antibiotics, anti-inflammatory drugs, and/or altrenogest, a drug that is used to help maintain pregnancy.
Among the treated mares, 90% carried foals to term and delivered successfully compared with 91% among mares that showed no abnormalities and were not treated.
Another finding of the study was that ultrasound examination can identify other significant causes of foal loss such as circulatory problems.