05/02/2002 11:00PM

New MRLS cases pop up

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LEXINGTON, Ky. - There is evidence that mare reproductive loss has returned this spring, and Eastern tent caterpillars are once again the leading suspects.

News that MRLS may have caused a handful of abortions has raised fears among Kentucky's breeders that last year's mysterious wave of abortions, which caused thousands of equine abortions and cost the industry an estimated $250 million, might strike again. But Kentucky's veterinary authorities stress that, so far, the effects of MRLS are much less dramatic this year.

The Kentucky Association of Equine Practitioners reported Thursday that "a few isolated cases consistent with a diagnosis of MRLS have been identified in the last seven days."

The KAEP statement emphasizes that the apparent MRLS-related abortions this year are far less than the numbers breeders reported last year. So far this year, only three foals showing MRLS-related symptoms have arrived at Lexington's two equine hospitals.

In a KAEP meeting Wednesday, Dr. Tom Riddle of Rood & Riddle Equine Hospital in Lexington reported that ultrasound examinations of 103 mares pregnant for at least 42 days showed five early fetal losses, an abortion rate 62 percent lower than in a similar timeframe last year.

There also have been two cases of pericarditis, swelling of the sac around the heart, so far this year. Pericarditis was another problem that occurred in unusually large numbers last year.

The KAEP said that the vast majority of central Kentucky's horse farms have had no MRLS losses so far this spring.

In 2001, some horsemen and scientists suspected that the abortions might be related to a heavy infestation of Eastern tent caterpillars that ravaged fruit trees in central Kentucky last April. Central Kentucky has had a similar infestation this year, but scientists point out this year's caterpillar population appears smaller and more isolated in pockets of the countryside, thanks partly to aggressive spraying by worried farm owners.

Last week, UK scientists issued preliminary results from their study of caterpillars and fetal loss. In an ongoing experiment involving 29 mares in Lexington, entomologist Dr. Bruce Webb found that six of 10 pregnant mares exposed to caterpillars and their droppings, called frass, lost their fetuses. Six of nine mares exposed to frass alone aborted their fetuses, and three of 10 mares in the control group, which had limited exposure to caterpillars, also aborted.

"In terms of how the caterpillars are functioning, we don't know," Webb said.

Last year, UK scientists initially thought the caterpillars were ingesting cyanide from their main food source, wild black cherry trees, then delivering the cyanide to mares in nearby pastures. Tests on the caterpillars subsequently discounted the cyanide role.

"We've reproduced a syndrome," Webb said, "and now we want to see if we can sort things out a little."

Webb's team also is testing grass samples from the mares' pastures to see if, among other things, the frass might have encouraged toxic fungal growth on the grass, which might in turn have caused abortions. The results are due in about three weeks.

For now, researchers and veterinarians are encouraging breeders to limit their mares' contact with caterpillars. UK's College of Agriculture has issued advice on ways to control caterpillars, including washing them into buckets full of soapy water and cutting down and discarding their tent-like nests. Detailed instructions are available at www.uky.edu/ Agriculture/VetScience/mrls.

Surfside gives birth

Surfside, the champion 3-year-old filly of 2000, produced her first foal, a Danzig colt, on April 17 at owner W. T. Young's Overbrook Farm.

Surfside will return to Danzig for the 2002 breeding season.

* English and French champion Shadayid, winner of the 1991 One Thousand Guineas and dam of group winner Bint Shadayid, died in Kentucky last week at age 14 after producing a Seeking the Gold filly, The Racing Post reported Friday. The filly survived. Shadayid, a daughter of Shadeed and Desirable (Ire), by Lord Gayle, won the Group 1 Prix Marcel Boussac, the One Thousands Guineas, and the Group 3 Fred Darling Stakes in her career and retired in 1991 with a record of 11-5-2-3 and more than $690,000 in earnings.