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Mare Reproductive Loss Syndrome

Following is a statement sent to State Veterinarians the morning of May 8, 2001
TO:  State Veterinarians

DATE:  May 8, 2001

SUBJECT:  Late term abortions and early fetal deaths among mares in Kentucky

Dr. Don Notter, Kentucky State Veterinarian, has asked that I provide you the following information.  We would imagine that many of you have heard about the situation currently occurring in Kentucky. In addition we will be keeping you apprised of any new information as it becomes available.  After you have had the opportunity to review this report, feel free to contact either Dr. Notter or myself should you have any additional questions.

Two clinical problems have been 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) in Lexington. Symptoms in mares would 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.

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 again affects more than one breed of horse.

We have asked our practicing veterinarians to 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.

We have been meeting and gathering information in a collaborative effort with local equine practitioners, faculty at the Livestock Disease Diagnostic Center 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. Discussions have 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.

At this time, though nothing has been ruled out, it would appear that the source of one or both of these events may be an environmental issue.  We have not identified any agent (viral or bacterial) which would suggest this to be a contagious situation.

E.S. Rusty Ford
Equine Programs Manager

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