04/02/2004 1:00AM

Still searching for MRLS cause

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LEXINGTON, Ky. - Mare abortion rates in central Kentucky are no longer alarmingly high, as they were during the mysterious mare reproductive loss syndrome in 2001. But the drop in abortion rates hasn't made breeders or researchers any less vigilant about the Eastern tent caterpillar.

So far, no one has identified the exact cause of MRLS, but researchers in Kentucky and abroad are reaching a general consensus that the caterpillars are involved. University of Kentucky researchers induced abortions in mares fed crushed caterpillars, a compelling result that has led many scientists to believe the Eastern tent caterpillar is the culprit - but how does it cause the disease? For hands-on breeders and farm managers, the differences of opinion about the cause of MRLS can be confusing as scientists work through their theories.

University of Kentucky scientists have focused on the setae, stiff hairlike projections on the caterpillars' bodies. Scientists believe that when a mare eats the setae, they can penetrate her gut lining, allowing bacteria to enter her bloodstream and move from there to the placenta, ultimately causing placental disease and abortion. Others theorize that cyanide, once a leading suspect but now largely dismissed by UK researchers, may indeed play a role.

One proponent of the cyanide theory is Dr. Twink Allen, a prominent English researcher who is an expert on the equine placenta. Allen theorizes that the caterpillars, who feed on cyanide-laden cherry leaves, may in fact expose the mares to the poison, which, when it collects in the capillary network of the placenta, causes placental irritation and even placental detachment and abortion. Experiments by University of Kentucky entomologist Dr. Bruce Webb showed that cyanide is detoxified in the caterpillar's foregut. But Allen wonders whether the cyanide might emerge in different ways, such as through the caterpillars' silky trails, which they use as highways to mark out their route along trees, grass, and fences.

Allen refers to studies showing that caterpillars recently fed cherry leaves caused mares to abort much faster, within two days, than caterpillars who hadn't been fed the leaves (10-12 days). He would like to see experiments examine fetal death as it is occurring, by surgically examining the fetus during the critical time frame after exposure to caterpillars, as a way to discover MRLS's exact cause.

"The local veterinary surgeons have done excellent work in inducing abortion in mares," Allen said, referring to the UK studies that fed caterpillars to mares via stomach tube. "What hasn't been done, and what needs to be done, is to look at the site of death at the time death is occurring."

What about horsemen's frequent contention that horses just won't eat caterpillars? UK researchers and Allen agree that ingestion might not be the only way mares are exposed to whatever toxin the caterpillar carries. The silky trails, exposure of the caterpillars' skin to water in troughs, accidental ingestion of the setae instead of the entire caterpillar, all are possible routes of exposure, researchers theorize.

While scientists hash out their different theories, breeders and managers are left with one main option: control their farms' caterpillar populations. To that end, they got some advice Tuesday morning in Lexington at a public meeting with UK entomology professors Ken Haynes and Don Potter, who presented their research into the most effective trapping and spraying methods to prevent caterpillar infestation. Updated information on the MRLS studies and practical caterpillar control is available at the UK College of Agriculture's website at www.ca.uky.edu. Click on the Mare Reproductive Loss Syndrome link.

Code of conduct for English agents

English racing and breeding organizations are considering establishing a code of conduct for agents and breeders involved in private and public bloodstock sales, the Racing Post reported Friday.

Under such a code, The Jockey Club there has said it would accept an enforcement role that could result in transgressing agents being warned off the track.

English racing authorities announced the plan after a summit of organizations involved in the Thoroughbred sport.

The Jockey Club called the summit in response to a recent scandal over the proposed sale of a filly named Foodbroker Fancy, which resulted in a lawsuit in England last December. In that case, the judge accused bloodstock agent Charlie Gordon-Watson and trainer David Elsworth with engaging in "bribery" and "secret profits" after Gordon-Watson privately offered Elsworth 10,000 English pounds to ensure the sale of Foodbroker Fancy to an American client of Gordon-Watson's.

Elsworth, who trained the filly, already was to receive a 5 percent commission on the filly's sale from her owners, who, according to court reports, did not know of Gordon-Watson's "sweetener" in the deal. The case later was settled.