While there haven’t been any headlines about the various syndromes that affected a large section of the eastern and mid-western United States this spring, that doesn’t mean that researchers and practitioners aren’t hard at work. Kentucky, with its large and carefully scrutinized mare population, seemed hardest hit by the various problems that included late-gestation abortions, early gestation fetal losses, pericarditis (heart problems), and uveitis (eye problems).

However, informal surveys and reports from horse owners and veterinarians in other states seem to indicate that problems affected horses from Tennessee into Canada.

The exact cause of these problems, and whether they are actually associated, has not been proven. Researchers are following many leads, but the main theory still seems to be a weather-related trigger that somehow led to the cyanide-containing leaves of black cherry trees being ingested by horses.

Results of a detailed epidemiologic survey of farms in Kentucky are expected to be released soon. Noah Cohen, VMD, PhD, MDH, Dipl. ACVIM, an equine epidemiologist, will be on loan from Texas A&M University to the Kentucky Livestock Disease Diagnostic Center to assist the state in studying archived samples at the center and from private clinics.

An Aug. 16 meeting of the Kentucky Veterinary Medical Association’s emerging diseases committee brought together private practitioners, researchers, and state and federal government officials. It was discussed that the problem with foal losses this year isn’t a new problem. It has occurred in past years (specifically 1980 and 1981), although not to the extent seen in 2001. The good news of that discussion was that in 1981 and 1982, practitioners reported no problems with deformed foals or getting mares in foal whether they had been affected by foal loss or not.

Mares Appear Normal

Richard Holder, DVM, a practitioner with the Lexington, Ky., firm of Hagyard-Davidson-McGee, sees a tremendous number of pregnant mares each year because of his specialty of sexing fetuses. Holder is gathering information about what is normal as far as cloudiness of the placental fluids in mares. Based on past experience and studies this year of healthy pregnant mares from overseas, Holder says that there seems to be a normal gestational pattern that involves some degree of cloudiness of the placental fluids.

Tom Riddle, DVM, and Kent Vince, DVM, of Rood and Riddle Equine Hospital in Lexington are completing a study comparing allantoic and amniotic fluids and heart rates of fetuses in mares bred in Kentucky with mares bred in Florida. In looking at 84 mares in Florida on six farms, they found it was normal to have echogenic (cloudy) allantoic and amniotic fluids beginning at 85 days of pregnancy and continuing through 150 days (the oldest Florida pregnancy checked).

The heart rate study also showed no differences in fetuses between the two states. Fetal heart rate is used as a measure of fetal stress.