Among the hot topics this year were nutritional supplements, infectious disease, and metabolism problems.

What do nutritional supplements, infectious diseases, and snake bites have in common? All were considered "hot topics" in equine health at the 2008 American College of Veterinary Internal Medicine (ACVIM) Forum held at the Henry B. Gonzalez Convention Center in San Antonio, Texas.

According to Jenn Armbruster, communications and media relations manager for the ACVIM, "2,566 veterinarians, 375 technicians, and 92 veterinary students attended, and approximately 300 scientific sessions, and more than 350 posters and oral research abstracts, were presented at this year's conference."

In this article we will relate the hottest topics presented during the equine portion of the seminar.

Nutritional Supplements

Four speakers contributed information on various aspects of supplementation in the nutrition session, demonstrating the continued popularity and widespread interest in this topic among equine practitioners.

An overview of the use of some dietary supplements, including minerals, herbs, vitamins, and nonherbal organ-specific products, was presented by Meri Stratton-Phelps, DVM, MPVM, Dipl. ACVIM, ACVN, of the University of California, Davis, School of Veterinary Medicine.

Stratton-Phelps cautioned that many supplements are void of scientific data regarding efficacy or safety, and that only after establishing the overall health of the horse should an individualized supplementation program be developed.

John Caron, DVM, MS, Dipl. ACVS, professor in equine surgery at Michigan State University's College of Veterinary Medicine, discussed the role of glucosamine and chondroitin sulfate-containing nutritional supplements and the potential impact of these products on clinical sign and disease progression in horses with osteoarthritis. His take-home message was that oral joint health supplements containing chondroitin sulfate and glucosamine appear to be effective, yet further research is necessary to characterize which horses are more likely to respond to supplementation.

The use of antioxidants and microbial supplements (i.e., yeast, prebiotics, and probiotics) was discussed by Carey Williams, PhD, equine extension specialist and assistant professor at the Equine Science Center at Rutgers, The State University of New Jersey, and Robert Van Saun, DVM, MS, PhD, Dipl. ACT, ACVN, an extension veterinarian and professor of veterinary science at Penn State, respectively. The speakers each reviewed the available data and literature to provide a comprehensive look at the current understanding of these products in horses.

According to Williams, "There is definitely a lack of well-designed clinical controlled studies in horses with enough power to truly support the widespread use of these popular products. More research is definitely required." (See article #12159 at for more information.)

Infection and Infectious Diseases

In addition to the ever-popular discussions centered on methicillin-resistant Staphylococcus aureus infections, equine infectious anemia, and equine viral arteritis, various other bacterial and viral diseases earned their time under the microscope at the Forum.

Co-author Carlos Medina-Torres, DVM, MSc, of the Ontario Veterinary College in Canada, described how he and his colleagues compared the diagnostic ability of the cytotoxicity assay (the current gold standard test) with the C. DIFFICILE TOX A/B II ELISA (enzyme-linked immunosorbent assay) test to detect toxins produced by the bacterium C. difficile.

The researchers reported a high level of agreement between the two tests, suggesting that the ELISA is a reliable test that can be used in the clinical setting to rapidly diagnose C. difficile-associated diarrhea in horses. (See article #12261 at for more information.)

Another bacterium-based research abstract was presented by Nicola Pusterla, DVM, PhD, Dipl. ACVIM, associate professor in the Department of Medicine and Epidemiology at UC Davis' School of Veterinary Medicine, on exposure of foals to Lawsonia intracellularis.

Pusterla and colleagues evaluated blood and fecal samples from 68 mare and foal pairs on a farm endemic for equine proliferative enteropathy (a disease of the gastrointestinal tract characterized by abnormal growth of the wall of the intestine) caused by L. intracellularis.

"During the 11-month study, one-third of foals showed evidence of natural exposure to L. intracellularis, but none of the foals developed clinical signs of equine proliferative enteropathy, despite the high exposure rate," said Pusterla.

Further, Pusterla and colleagues showed that healthy broodmares and foals do not commonly shed L. intracellularis in their feces; therefore, they are not a likely source of infection to susceptible animals. (See article #12383 at for more information.)

On the viral front, Elizabeth Carr, DVM, PhD, Dipl. ACVIM, ACVECC, assistant professor in the Department of Large Animal Clinical Sciences at Michigan State University's College of Veterinary Medicine, presented a study on equine herpesvirus-1 (EHV-1) recrudescence (breaking out afresh) and viremia in hospitalized critically ill horses.

Carr explained that the factors that trigger nasal shedding in horses latently infected with EHV-1 remain unclear.

To assess the impact of stress and disease on nasal shedding of EHV-1, Carr and colleagues evaluated 122 hospitalized critically ill horses older than 6 months of age. They collected blood samples and nasal secretions from horses and tested them for EHV-1 using a polymerase chain reaction test (a DNA test).

"Our results showed that not one of the hospitalized horses was positive for EHV-1, suggesting that shedding of EHV-1 is extremely rare in these cases," said Carr. (See article #12281 at for more information.)

In the ACVIM Equine Generalist session, Paul Morley, DVM, PhD, Dipl. ACVIM, director of biosecurity at Colorado State University, described some of the key lessons he and his colleagues have learned while developing the university's biosecurity program in his presentation, "Infection Control: A Decade of Lessons Learned."

Morley advised that communication, industry compliance and buy-in, and lack of data are all issues that need to be addressed to improve biosecurity in veterinary hospitals. (See article #12315 at for more information.)

Finally, during the ACVIM Equine Specialist session, Michelle Henry Barton, DVM, PhD, Dipl. ACVIM, professor of large animal medicine at the University of Georgia's College of Veterinary Medicine, said, "Rats are not people and people are not horses." She addressed the complexities of studying endotoxemia (the presence of life-threatening bacterial-derived endotoxin in the bloodstream) in horses.

Specifically, Barton reviewed the pathology of endotoxemia, described various mammalian models of studying endotoxemia, and took an in-depth look at the "big picture" surrounding endotoxemia in adult horses and foals and the challenges associated with managing cases of advanced sepsis (bacterial infection in the blood circulation) and endotoxemia. This includes the development of systemic inflammatory response syndromelike clinical signs, multiple organ dysfunction syndrome, blood clotting abnormalities, and the development of laminitis.


The science of seasons To everything there is a season, and season does impact equine metabolism, according to Kibby Treiber, PhD, of Virginia Tech, and Christopher Schreiber, a veterinary student at Auburn University.

Treiber and colleagues evaluated potential seasonal implications with laminitis in grazing ponies by measuring pasture carbohydrates and various metabolic parameters in pastured ponies.

Nine of the nearly 30 ponies developed laminitis during the study. When researchers compared laminitic ponies to nonlaminitic ponies, they found significantly higher insulin and triglyceride levels in laminitic ones. In addition, all ponies had the highest glucose and insulin levels in the spring, whereas triglyceride and nonesterified fatty acids were lowest at that time of year. Those changes in metabolism in combination with high insulin levels or insulin resistance might contribute to the development of laminitis in the spring.

Schreiber and colleagues tried to determine if season impacted the results of various pituitary function tests in normal horses residing in Alabama.

While the researchers identified significant differences in á-melanocyte-stimulating hormone based on season, the overall seasonal effect on tests for pituitary pars intermedia dysfunction was less obvious in Alabama compared to tests on horses residing in the northeastern United States. (See article #12317 at for more information.)

Insulin sensitivity/resistance In addition to meteorologic metabolism, insulin sensitivity and insulin resistance in horses were also timely and popular topics in the equine sessions. Rebecca Carter, a PhD candidate from Virginia Tech, presented study results showing that increased adiposity in horses is associated with decreased insulin sensitivity, but unchanged inflammatory cytokine (immunoregulatory proteins) expression in subcutaneous adipose tissue.

Ferenc Toth, DVM, PhD, of the University of Tennessee, described the effects of pre-treating horses with dexamethasone or levothyroxine before inducing insulin resistance with endoxtoxin. Toth and colleagues evaluated whether resting insulin sensitivity could affect the magnitude of insulin resistance caused by endotoxin. (See article #12344 at for more information.)

Other Topics in Equine Medicine

Two unique presentations in the ACVIM Equine Generalist session focused on rattlesnake bite management and use of radiation therapy in equine oncology.

Just another snake bite? Lyndi Gilliam, DVM, Dipl. ACVIM, assistant professor in the Department of Veterinary Clinical Sciences at Oklahoma State University's Center for Veterinary Health Sciences, advised that with more than 26 species of rattlesnakes in the United States, rattlesnake bites in horses are not an uncommon event.

Gilliam succinctly described the short- and long-term management goals when treating horses with rattlesnake envenomation and encouraged a 12-month post-bite examination to assess the horse's cardiovascular system, as cardiac dysfunction caused by a component of rattlesnake venom is a relatively common complication. (See article #12185 at for more information.)

Radiation therapy Janean Fidel, DVM, MS, Dipl. ACVR, ACVIM, of Washington State University's College of Veterinary Medicine, described the basics of radiation therapy and encouraged practitioners to consider this treatment modality in horses with such cancers as sarcoids or melanomas.

"Radiation therapy is a valuable tool in the treatment of our equine oncology patients."--Dr. Janean Fidel

"Even though cancer is not as common in horses as dogs or cats, it does still occur, and just like in small animals, radiation therapy is a valuable tool in the treatment of our equine oncology patients," emphasizes Fidel. "Any body part that fits under the beam can be treated."

Six American colleges of veterinary medicine currently offer radiation therapy for equine patients: Auburn, the University of Missouri-Columbia, Ohio State, Texas A&M, UC Davis, and Washington State. (See article #12235 at for more information.)

The 2009 Lineup

The 27th annual ACVIM Forum is scheduled for June 3-6, 2009, in Montreal, Canada.

According to Armbruster, "The 2009 Forum is destined to be a unique conference in that the ACVIM and the Canadian Veterinary Medical Association Convention will be joining forces and hosting their continuing education events together. Therefore, we are marketing the event as the 2009 ACVIM Forum & Canadian Veterinary Medical Association Convention."

More information is available at

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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