Updated on 09/15/2011 12:25PM

Heart ailment the latest cause of concern

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LEXINGTON, Ky. - Mare reproductive loss syndrome (MRLS) the mysterious ailment that has caused more than 1,000 central Kentucky mares to abort their foals, appears to be on the wane as research continues into its cause. But another problem, this one much less widespread but still of concern, has surfaced: pericarditis, fluid in the sac that surrounds a horse's heart.

Dr. Johanna Reimer, a veterinarian at Lexington's Rood and Riddle Equine Hospital, said this week that there have been about 60 cases reported in the area since late April, 10 of which have been in her care. Two of those horses were euthanized. "Normally, I'd see about one case a year," she said.

The fact that veterinarians began noticing the heart problem - which causes respiratory distress and fever - in late April and early May has some wondering whether it is related to MRLS, but so far the causes of both diseases have not been identified, let alone linked. Current theories about the MRLS cause range from cyanide to hemlock to fungus and mold on pasture grass, but investigations continue.

It's possible that pericarditis is attacking horses weakened by another problem - perhaps the causative agent for MRLS - but Reimer thinks that's unlikely. But she does think the two diseases may be linked. "I don't think the pericarditis is due to immunosuppression, because we aren't seeing more cases of the more common diseases we know would be present. The pericarditis pattern appears to fit with environmental exposure, as does MRLS."

Reimer, who believes fungus-produced mycotoxins or grass endophytes are a likely cause of MRLS, now suspects that the pericarditis may also be related to fungus. "Outbreaks or epidemics of pericarditis are associated with histoplasmosis, where the horse will get a mild infection of the pulmonary lymph nodes. Usually, they will clear that, but then they get pericarditis. I'm thinking that the mechanism - although not histoplasmosis, because all but one horse has tested negative for it, and that one was mild - has a similar action as histoplasmosis. I would think fungus would have to be high on the list, and some clues, like horses having fevers and fungal pneumonia, suggest that."

But, like her colleagues researching MRLS, Reimer notes that research so far is incomplete. In the meantime, instances of pericarditis appear to be lessening, much to the relief of area horse owners concerned about another round of equine disease.

MRLS may finally be stopping, but the Kentucky Thoroughbred Association and Kentucky Thoroughbred Owners and Breeders Association, calling its own estimates "conservative," is projecting that there will be a $50 million direct economic impact on the state this year, followed by a $350 million direct impact next year. With few figures available for early fetal losses, the KTA/KTOB also projects that 5 percent of the 2001 Kentucky foal crop has been lost and predicts a loss of at least 20 percent of the 2002 crop. Kentucky annually produces about 10,000 foals.

Mares were still losing pregnancies in early June, according to some local vets.

"I saw losses anywhere from 21 days through 60-plus days last week," said Dr. Kerry Zeigler, who also is a breeder. "The losses are down significantly from the epidemic proportions I saw around Derby weekend [May 5]. Hopefully, it waned through the early part of the month of June, it seems that it may have discontinued."

Like many, Zeigler has treated mares with domperidone, a medication that is used to prevent or treat fescue toxicosis in mares late in pregnancy.

"What concerns me is that we don't know what we're treating, and this drug, whose use has been widespread during the MRLS problem, isn't approved for use in early pregnant mares," she said. Zeigler added that the drug, usually given for two to three weeks, has become a month-long treatment for some mares that breeders consider to be at risk. "When it comes down to it, we just don't know. That's the most disturbing part."

Paseana back, still troubled

Champion Paseana, who has only produced one foal since her retirement in 1995, has returned to the United States from Argentina, where an equine fertility specialist had been enlisted to help her get in foal. But hopes that the venerable racemare will be bred to Skip Away in North America are fading fast.

Paseana, voted champion older mare in 1992 and 1993, produced her sole offspring, a 2000 filly by Lode, during her three-year Argentine sojourn. Owner Sidney Craig shipped her to Lane's End Farm in Versailles, Ky., in February, but with the breeding season set to end within two weeks, Paseana has yet to ovulate.

"She hasn't cycled normally all year, and she hasn't been making a normal follicle," said Mike Cline, manager of Lane's End. "I can't explain what's happening with her, but we've tried a little bit of everything. "More than likely, we won't get her bred this year. Maybe more time to acclimate here will help."