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Mare Reproductive Loss Syndrome

Late term abortions and early fetal deaths among mares in Kentucky, May 7, 2001

Two clinical problems were reported on a number of farms in Kentucky during the week commencing April 30, 2001.

1.   A significant number of late term aborted fetuses have been submitted to the Livestock Disease Diagnostic Center (LDDC).  Symptoms in mares include agalactia, dystocia and stillbirths.  A number of foals were born weak and a few only survived four days.  Placentas associated with a number of these losses have been thickened and edematous, consistent with red bag syndrome.  Several breeds of horses have shown these signs.
Investigations into all possible causes of these late term abortions are ongoing.  The fetus and placenta should be bagged and promptly delivered to the local diagnostic laboratory.

2.   The second condition relates to an increased number of mares determined to be in foal at ~40 days but subsequently on ultrasound examination (45-80 days) have undergone early fetal loss (EFL).  Affected mares feel normal on rectal palpation at 60-65 days gestation, but on ultrasound examination, abnormal eccogenic fluid (cloudy and flocculent) is seen around the fetus.  This is followed by fetal death and expulsion.  A number of mares have exhibited a vaginal discharge and occasional fever.  The incidence of EFL on affected farms has varied considerably with cases reported on farms in several counties of central Kentucky.  The problem affects more than one breed of horse.

Veterinarians should consider ultrasounding mares at 60-65 days of gestation.  If the mare aborts, any fetal tissue found and a serum sample from the mare should be submitted to the diagnostic laboratory.  Fetal tissue should be kept chilled and delivered as soon as possible.

On Thursday, May 3, 2001, several veterinarians who had reported cases met with faculty of the UK Department of Veterinary Science and a nutritional consultant to evaluate the situation.  Discussion included the extent and distribution of the cases and what material, including pasture samples needed to be examined in order to establish an etiologic diagnosis.

An intensive collaborative effort is underway with local equine practitioners, faculty at the LDDC and the Maxwell H. Gluck Equine Research Center, farm managers, nutritionists, and others.  The investigations include studies to evaluate whether these two problems share a common etiology.

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