The “blip” of abortions seen in August, September, and October in Kentucky has continued on through December. With only about 50 total abortions reported, this problem might not even catch the attention of many people in a normal year, as breeders expect to lose about 5% of fetuses prior to foaling. But following the occurrences of mare reproductive loss syndrome (MRLS) the past two years, any reproductive anomalies are being scrutinized. What makes these abortions unique is that they are only occurring on a few farms (reported to be between six and eight), with two or more abortions occurring in a single group of mares, and other mares not affected at all.

Lenn Harrison, VMD, head of the University of Kentucky Livestock Disease Diagnostic Center, said pathologic features seen in these mid-term abortions are not “strongly reminiscent of MRLS.” He said in discussions with pathologists in the Diagnostic Center and with specialists outside Kentucky, no one is willing to associate the current abortions with MRLS based on pathologic findings.

In looking back at six years’ of abortion reports at the Diagnostic Center, there is no statistical difference in the number of abortions this year from the average, said Bill Bernard, DVM, Dipl. ACVIM, president of the Kentucky Association of Equine Practitioners and an internal medicine specialist at Rood and Riddle Equine Hospital.

Some good has come from all the reproductive problems of the past two years, noted several researchers and practitioners—there have been increases in the willingness to share information and the desire to be proactive at all levels of the industry. In years past, many farms with abortions would not bother to report anything or even take the fetus to the laboratory, simply chalking the loss up to the normal 5%. Today, there is a tremendous effort made to take fetuses to the Diagnostic Center for study.

To assist in maintaining records and easing retrieval of all this information, a new data collection and retrieval computer system will be designed and installed at the Diagnostic Center, reported an enthusiastic Bernard. This Equine Reproduction Health Data Information Repository will enable pathologists to have a standardized form to store information about each case, will include information from the referring veterinarian, and will permit information from farm follow-up to be entered in the system.

More good news, said Bernard, is the heightened awareness of the need for a full-time epidemiologist at the Diagnostic Center, and the hope that position will be created and filled quickly.

Surveying the Situation
The University of Kentucky’s Gluck Equine Research Center has been called upon several times during the past two years to survey the industry to help gather and analyze information during the MRLS crisis. They again have taken up the yoke of gathering information from farms affected by the current abortions, and farms that have not been affected.

One of the important pieces of information that will be gathered is attempting to get an appreciation of the size of the pregnant mare population in Central Kentucky, noted David Powell, BVSc, an epidemiologist at the Gluck Center. He said it is assumed the population of mares has been increasing over the last five years, so the population of at-risk mares also has increased. One piece of information to be ascertained will be the number of mares covered from February to June of this year, and how many of those are still pregnant as of the end of November.

Powell said researchers, including Roberta Dwyer, DVM, Dipl. ACVPM, will continue to gather information from farms through tomorrow (Dec. 19). The next stage is to complete data entry based on the surveys, including contacting the farms to “clean up” information provided. Then the analysis of the figures will go into the new year, with final information available sometime in January.

The University of Kentucky will post information on its web site as it did during the MRLS crisis, said Powell. That address is

From the Field and Clinic
“I don’t think we have an answer,” said Doug Byars, DVM, Dipl. ACVIM, head of the Haygard-Davidson-McGee veterinary firm’s medicine facility. “This has been premises oriented,” he noted, but added that while farms with MRLS during the 2002 breeding season seemed more prone to the mid-gestation abortions, other farms without MRLS this foaling season also had abortions in the fall. He said the medicine facility had three mares admitted with dead/dying fetuses in the last 10 days, which isn’t a large number.

He and other practitioners added that some people might be making “inappropriate assumptions” as to the cause of these abortions, which haven’t been related to MRLS at this time.

Private practitioner Steve Conboy, DVM, said that while the farms he serves had a couple of abortions one to two months ago, he hasn’t seen any since that time. He said the mares had a placentitis (infection in the placenta) shortly after weaning time, “but I can’t say this is a greater number (of abortions) than normal,” he added. “The diagnostic lab’s statistics show this is not too far out of the range of normal (for the number of abortions).”

“I think everyone is still fairly convinced of the association (of MRLS) with Eastern tent caterpillars,” said Conboy. “But we won’t close our eyes to any possibilities. I think the Eastern tent caterpillar theory holds the most promise (for causing MRLS). I don’t think we can say these abortions (in the fall) are related to MRLS. There’s no scientific evidence to suspect they are related. It’s not a big ‘abortion storm,’ but we don’t know what’s causing it.”

He reiterated Bernard’s feelings that the MRLS crisis has opened communication paths and increased knowledge the past couple of years, but “we can’t go back too far to compare” numbers with the increased surveillance and reporting of abortion problems in the past two years.

Something New?
One veterinarian brought up the possibility that a protozoan organism might be causing some of the problems with abortion in mares. (Equine protozoal myeloencephalitis, EPM, is caused by a protozoan parasite, you might recall.) The protozoan parasite mentioned was <I>Encephalitozoon cuniculi<I>. Information from medical references notes that this intracellular parasite is found in the brain, heart, and kidneys of several mammals. Transmission is probably by ingestion of the spores.

An article abstract was published earlier this year in a veterinary journal noting that a Quarter Horse mare in Kentucky had aborted and been discovered by a pathologist at the Diagnostic Center to have this rare protozoan parasite. Harrison said that <I>E. cuniculi<I> is “very unlikely” to be associated with MRLS. He said pathologists at the Diagnostic Center had identified the case and were clearly able to see pathologic changes associated with a protozoan infection.

About the Author

Kimberly S. Brown

Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.

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