GPS use on track, new test for EPM, and upper airways in sale weanlings discussed at AAEP convention

THE THIRD-LARGEST crowd in the 51-year history of the annual convention of the American Association of Equine Practitioners turned out for this year's event in Seattle on December 3-7, with 2,958 veterinarians, 1,948 exhibitors, and 929 guests making the trek to the Pacific Northwest.

Horseman's Day, an annual event that brings together some of the top names in horse health to speak to laymen about day-to-day horse issues, drew about 250 attendees.

This year, Thoroughbred practitioners and professionals were presented a wealth of information on issues that affect athletic performance, valuation of horses at public auction, and breeding.

GPS to monitor fitness

Trainers can look forward to using a combination of global positioning system (GPS) and heart-rate monitor technologies to assess the fitness of racehorses in training, according to David Evans, B.V.Sc., Ph.D., an Australian researcher who has been working with manufacturer Nature Vet Pty. Ltd. to develop a commercial application for racetrack use.

Evans, associate professor of veterinary science at the University of Sydney, explained that until he began this study, the gold standard for judging aerobic fitness in a racehorse was a treadmill test for maximum oxygen uptake, or how much oxygen a horse's body uses to manufacture energy and cleanse its blood of fatigue-causing lactic acid.

Evans said the challenge was to develop a system that was:

• A simple measure of fitness on the track;
• Noninvasive;
• Acceptable to trainers and jockeys;
• Rugged enough to be carried by a horse in training; and
• Able to produce meaningful data.

During his study, Evans worked with Australian trainer Clarry Connors to outfit each of his 12 two-year-olds in training with a heart-rate monitor and each horse's jockey with a GPS transmitter in his helmet. The systems worked together to transmit data on the horse's speed (velocity) and its corresponding heart rate while the juvenile exercised on the track.

The horses were assessed before and after four weeks of advanced training, during which they were exercised at a trot and slow gallop four days per week, breezed two days per week, and rested one day per week. This was a typical training protocol for Connors's two-year-olds, Evans said.

The commercial version of this new technology, which Nature Vet hopes to make available early in 2006, will use software loaded onto a laptop computer to receive and analyze the data at trackside while the horse exercises.

New EPM test

Martin Furr, D.V.M., Ph.D., chief of medicine at the Marion duPont Scott Equine Medical Center in Leesburg, Virginia, presented results of his research into a novel diagnostic tool for equine protozoal myeloencephalitis (EPM) using an equine gene chip and biomarkers.

A simple diagnostic blood test for an active EPM infection has been difficult to develop because horses with casual exposure to the disease and those that have been vaccinated against EPM also have antibodies against Sarcocystis neurona, the pathogen that causes the disease, circulating in their blood. So, blood tests often produce false positives. Invasive spinal taps to test the cerebrospinal fluid are required for more accurate results, but, until now, a definitive diagnosis of EPM only could be obtained by post-mortem examination.

Affymetrix Inc., a genetic technology company based in Santa Clara, California, and Genetraks Holdings in Bethesda, Maryland, collaborated with Furr in producing a computer chip that can be used to look at a pattern of activity, called gene expression, in circulating white blood cells that would indicate an active EPM infection and discern it from casual exposure and response to EPM vaccination.

Gene expression means that certain genes that react to the disease begin to express proteins. Identifying those active genes and how they interact, then linking them to the specific disease that causes them is called a diagnostic signature. This technology does not look at DNA; it only looks at genes that are actively expressing proteins.

"We developed a diagnostic signature for EPM that proved highly accurate, at least in the acute phase of infection--up to 28 days," Furr said. "We'll probably be seeing more work being done with this methodology because it is so strong."

The genomic biomarkers are expected to be able to provide information on the stage of disease and the prognosis, as well as a means to monitor the progression of the disease and its response to treatment. Additionally, Furr hopes it will give clinicians a means to detect EPM before clinical signs emerge, enabling them to stop the progression of the disease before it causes damage to the central nervous system.

"We had an overall specificity of 95% to 98% in classifying these horses [with laboratory-induced EPM]," Furr said. "There are studies ongoing looking at diagnostic efficiency of this technique in naturally occurring cases. We can't give you a timeline on when this test may become available, but we hope it will be in the next few months when a commercially available test will be in use."

Advances for joint disease

C. Wayne McIlwraith, B.V.Sc., Ph.D., director of Colorado State University's Orthopaedic Research Center, presented this year's Frank J. Milne State of the Art Lecture. McIlwraith, a pioneer in arthroscopy and one of the world's leading researchers into osteoarthritis, outlined advances in both areas.

McIlwraith told listeners that joint-related diseases are the most common cause of lameness in athletic horses, and osteoarthritis even occurs in wild horses, so it is not a manmade phenomenon.

In the past, concussive forces of the horse impacting the ground were thought to be one of the factors in the development of joint disease. "Muscle forces across the joint are double ground forces," McIlwraith said of new information on gait kinetics.

"Conventional medications still form a large part of the equine veterinarians' armamentarium," McIlwraith said. "Increased attention is being paid to physical therapy regimens and positive results demonstrated with shock-wave therapy, and [these] can perhaps decrease the use of medication for equine joint disease. COX-2 inhibitors are going to be useful to the veterinarian when the patient is not tolerating phenylbutazone well."

Although McIlwraith called efficacy of oral joint nutraceuticals "a black box," he noted that a new supplement, Vtoquinol, which is not yet available in the United States, has shown positive results in a controlled study.

David Frisbie, D.V.M., Ph.D., one of McIlwraith's colleagues at CSU, presented the results of his work using biomarkers and a gene chip array as a diagnostic tool for osteoarthritis and a means to track the progression of joint disease and its response to treatment.

Grading throats at sale

In the first study of its kind, Scott Pierce, D.V.M., a practitioner at Rood & Riddle Equine Hospital in Lexington, graded the upper respiratory tracts of 371 Thoroughbreds between 2000 and '04 to determine how maturing affected the grade as the horses progressed from weanlings to yearlings. The study attempted to define which conditions the horse would grow out of, which stayed the same, and which worsened with age.

"Needless to say, this is a controversial exam with lots of differences of opinion," Pierce said. "There's a lot of money in play here, so many times our opinion will influence the sale price of the individual."

The horses' throats were graded on a scale of I to IV, based on physical characteristics of the throat structures and how efficiently they functioned, with I being the best and IV being the worst. The initial examination was performed on weanlings at the Keeneland November breeding stock sale; the second examination was performed on the same horses at yearling sales at Keeneland, Fasig-Tipton Kentucky, and Fasig-Tipton Saratoga.

Arytenoid function stayed the same or improved in 92.2% of the horses studied, but in 35.1% of the horses, epiglottis grades worsened at least one grade. "The results of this study show that the upper respiratory tract of a young Thoroughbred horse tends to improve from weanling to yearling," Pierce said.

"This is interesting," he added. "One Grade III [in the study] that came back through the yearling sale had a [Grade] IIB, which is an excellent airway." (Grade III airways have been shown to have a detrimental effect on performance.)

"For the buyer," Pierce concluded, "you can't be as critical of an airway in a foal." He urged sale companies to reconsider their conditions on lack of wind.

Inflammation in broodmares

Thomas Riddle, D.V.M., one of the founders of Rood & Riddle, joined forces with internationally acclaimed theriogenologist Michelle LeBlanc, D.V.M., and Pierce to investigate the relationship between uterine inflammation, as shown in cultures and biopsies, and the rate of conception in 970 barren and foaling mares during the 2001 to '04 breeding seasons, excluding those that suffered from mare reproductive loss syndrome (MRLS).

The investigators found that almost twice as many mares with inflammation serious enough to affect conception were identified through uterine cytology (biopsy) than culture swabs. Results also indicated that the widely held belief that bacteria in the uterus that do not cause inflammation are innocuous was false because these mares had lower pregnancy rates. Riddle said inflammation may still be present, but it might be deeper in uterine tissues where it is not readily detected.

"By performing a uterine cytology, mares with uterine inflammation can be identified more quickly than by uterine culture because samples can be processed and interpreted by laboratory personnel or by the veterinarian the same day the sample is taken," Riddle said. "Mares identified as having uterine inflammation can have additional diagnostics performed before breeding in an attempt to determine the source of the inflammation."