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Mare Reproductive Loss Syndrome Index Page

February 8, 2002

Status Report on MRLS
University of Kentucky College of Agriculture

The exact cause or mechanism of MRLS remains unknown. The University of Kentucky College of Agriculture has not changed the interpretation of risk factors associated with MRLS and continues to recommend the same preventative measures first published in October of 2001.

The primary preventative measures include:

1)  Minimize or eliminate exposure of pregnant mares to the Eastern Tent Caterpillar.
2)  Keep pregnant horses out of proximity to wild cherry trees.
3)  Frequently clip pasture used by pregnant mares.
4)  Offer hay to horses on pasture.

Epidemiological studies conducted by the University of Kentucky identified the presence of moderate to heavy infestations of eastern tent caterpillars as one of the factors associated with increased MRLS.  However, laboratory experiments at the University of Kentucky indicate that direct transfer of cyanide from wild cherry leaves to pregnant mares by the eastern tent caterpillar is unlikely. Monitoring and experimental studies will continue to assess the possible indirect roles of eastern tent caterpillars in MRLS. Consequently, eastern tent caterpillar management remains a part of the overall recommended MRLS risk reduction program.

The University of Kentucky monitoring program involves active surveillance of pastures, soils and horses on selected farms in central Kentucky. The University of Kentucky is aware of the Clemson University work on hemlock and the monitoring program will look for the presence of poisonous plants, including hemlock, and any subsequent problems in horses.

The University of Kentucky research program this spring will involve testing of several hypotheses about the cause(s) of MRLS.   Scientists at the University of Kentucky will examine the effects of exposure of pregnant mares to eastern tent caterpillars, as well as test the possible effects of mycotoxins, factors that mimic hormones (anti-estrogens), bacteria, cyanide and similar compounds.




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