Bloodstock Briefing: Foetal loss: caterpillar still main focus of suspicion.

Byline: Rachel Pagones

THE number of equine abortions has risen in central Kentucky compared to a year ago, but as yet the reason - or reasons - remain a mystery.

The University of Kentucky's Livestock Disease Diagnostic Center in Lexington has been keeping a weekly tally of equine abortions of all breeds in the state since January 1. To date, five of the six weeks tabulated show an increase in abortions compared to the corresponding weeks last year.

The specific numbers of abortions are: week one, 35 (up from 22); week two, 33 (31); week three, 26 (24); week four, 40 (22); week five, 24 (down from 30), and week six, 38 (up from 33). The cumulative total for 2003 is 196, compared to 162 for 2002.

However, clinics that received the aborted foetuses have found no evidence of mare reproductive loss syndrome (MRLS), which ravaged the foal crop of 2002. Around 500 foals were lost to the syndrome in 2001.

The state's breeding industry, by far the largest and most important in the US, is still feeling shockwaves from MRLS, which struck largely around April of 2001.

Last year's Keeneland November breeding stock sale was the smallest since 1993, with just 864 foals catalogued compared to 1,063 in 2001 and 1,379 in 2000. And Keeneland's July yearling sale - scene of legendary bidding battles in the 1970s and 1980s between Robert Sangster, John Magnier and Vincent O'Brien on one side and the Maktoum family on the other - gave way completely under the strain. With fewer yearlings in 2003, and particularly fewer with early birthdates, the sale was called off for the first time since its inception in 1943.

Researchers note that one possible reason for the increase in early abortions is simply that more mares were covered early last season as a result of having lost their pregnancies to MRLS the previous spring.

The University of Kentucky Department of Veterinary Science is continuing to post numbers of 2003 equine abortions on its MRLS website (www.uky.edu/agriculture/

vetscience/mrls/index.htm).

"We're continuing to post [abortion] accessions to the Livestock Disease Diagnostic Center," says Dr David Powell of the University of Kentucky's Gluck Equine Research Center. "As in the past, it's important to look at these accessions in terms of possible trends that may occur over several weeks rather than a slight increase reported for a specific week."

A SURVEY of central Kentucky horse farms has turned up possible risk factors linked to increased foetal losses during the autumn of 2002. The survey was conducted by the University of Kentucky's Gluck Equine Research Center and College of Agriculture.

The 30 farms involved in the survey filled out detailed questionnaires. Of these, 22 were control farms which had reported no apparent increase in the number of foetal losses, and eight were affected farms representing those with higher-than-expected losses. Veterinarians who worked with the eight affected farms were also interviewed.

Nine risk factors were identified by the study, and four were deemed significant: topical use of an insecticide, the presence of Eastern Tent caterpillars, the presence of MRLS and increased illnesses.

"These are only suspects, and as such are innocent until further evidence is obtained," says Powell. "We should also emphasise that we are dealing with a

multi-factorial situation. There could be a combination of causes or other factors, such as weather, that could have played a role."

THE Eastern Tent Caterpillar is still considered the most likely culprit, and as such has become the number one target for stud managers and scientists.

A think-tank meeting sponsored by the Kentucky Association of Equine Practitioners, the Kentucky Thoroughbred Association, Rood & Riddle Equine Hospital and

Hagyard-Davidson-McGee Associates brought together 31 vets and scientists in January to discuss the problem. Participants came from several states and from both public universities and private industry.

Their conclusion was that getting rid of the caterpillar is necessary but not sufficient, and that determining the precise link between insect and illness should be an industry priority.

"Eliminating the caterpillar is certainly our primary goal in terms of prevention, but we also have to find out exactly what's causing the problem," says Bill Bernard, president of the Kentucky Association of Equine Practitioners. "It's possible we could make a real breakthrough in reproductive health if we identified the toxin or agent that's responsible within the caterpillars."

There are currently two theories linking the caterpillar to MRLS. One assumes a virus or bacterium is acquired from the insect, while the other assumes that the caterpillar contains a chemical toxin.

"In light of these two competing approaches the group agreed that it makes a good deal of sense that the first step in our research should be to decide if it's biologic or chemical," Bernard says.

"The group also

expressed a strong interest in trying to establish a research model using an animal other than a horse, in other words the laboratory rat or mouse or guinea pig that could be used to test theories rapidly and inexpensively."