Case-control study of early-term abortions (early fetal losses) associated with mare reproductive loss syndrome in central Kentucky.

The research article focuses on understanding the factors linked with abortions in horses at an early gestational period, identified as mare reproductive loss syndrome (MRLS). The study involved examining 324 broodmares from different farms in Kentucky, looking at their management practices, and environmental exposures to identify potential risk contributors to MRLS-related early-term abortions (ETAs).

Methodology

• The researchers conducted a case-control study involving a total of 324 broodmares from 43 farms in central Kentucky.
• The mares were divided into three groups: 121 mares from 25 farms that experienced ETAs related to MRLS, 120 mares from the same farms but did not abort, and 83 mares from 18 farms that were not severely impacted by MRLS.
• Data were collected through interviews of farm managers about the management practices and environmental exposures for the mares.
• Information gathered from both case (mares with MRLS-associated ETAs) and control (mares without aborting or from less affected farms) groups was compared to identify risk factors associated with MRLS.

Results

• The study found several factors that may increase the risk of MRLS-associated early-term abortions (ETAs).
• These factors included: feeding hay in the pasture, a larger than usual population of white clover in the pastures, higher numbers of eastern tent caterpillars, the mare having had an abortive incident during a previous pregnancy, and sightings of deer or elk on the premises.

Conclusions

• The conclusions suggest that certain characteristics of pastures might predispose mares to experience MRLS-associated ETAs.
• Measures suggested to mitigate risks included isolating the mares, limiting their pasture exposure chiefly during environmental conditions similar to those witnessed in 2001 (like a sudden freeze in mid-April following warmer-than-usual spring temperatures and presence of higher-than-usual numbers of eastern tent caterpillars).
• The study indicates uncertainty about whether the exposure to white clover or caterpillars were causal factors for MRLS, or were merely indicators of unique environmental conditions that led to mares being exposed to a toxic or infectious agent.