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Article Outline
- AAEP Convention Breaks Attendance Record
- White Delivers State-of-the-Art Lecture at Annual Convention
- New Procedure to Correct Equine Heart Rhythm Problem
- Texas Horse Owners Urged to Implement Best Management Practices to Prevent Equine Viral Arteritis (EVA)
- Current Treatments for Equine Protozoal Myeloencephalitis
- Reproduction: An Emerging Focus at North Carolina State
- Ongoing Research
AAEP Convention Breaks Attendance Record
The 52nd Annual Convention of the American Association of Equine Practitioners (AAEP), held December 2–6 in San Antonio, Texas, set a new attendance record for the association's flagship event, as 6,842 veterinary professionals, guests, and exhibitors participated. The previous attendance record of 6,284 was set at the 2004 Annual Convention in Denver, Colorado.
“We were overwhelmed with the positive response to this year's convention. A fantastic and extremely practical program, coupled with a very popular convention city, set the stage to make this meeting our most successful ever,” said David L. Foley, AAEP executive director. “Our heartfelt thanks to all those involved for continuing to make the AAEP convention the best place for equine continuing education in the world.”
Highlights from the convention include:
The AAEP 53rd Annual Convention will be held in Orlando, FL, December 1–5, 2007. For more information, call the AAEP office at (859) 233-0147 or visit www.aaep.org.
The American Association of Equine Practitioners, headquartered in Lexington, KY, was founded in 1954 as a non-profit organization dedicated to the health and welfare of the horse. Currently, the AAEP reaches more than 5 million horse owners through its over 9,000 members worldwide and is actively involved in ethics issues, practice management, research, and continuing education in the equine veterinary profession and horse industry.
Contact: Sally J. Baker, APR, sbaker@aaep.org or (859) 233-0147
White Delivers State-of-the-Art Lecture at Annual Convention
Dr. Nat White, the Jean Ellen duPont Shehan Professor and director of Virginia Tech's Marion duPont Scott Equine Medical Center, presented the prestigious Frank J. Milne State-of-the-Art lecture at the American Association of Equine Practitioners (AAEP) 52nd Annual Convention in San Antonio, TX, on December 4, 2006. The dynamic address, “Equine Colic: A Real Pain in the Gut,” was attended by nearly 3,000 industry representatives and equine practitioners.
Using case examples from his clinical experience and research for illustration, White showcased advances in the diagnosis and treatment of colic in horses. Topics included the response of the intestine to inflammation, ischemia, and pain, as well as the clinical signs used by practitioners to diagnose colic and to select the most effective courses of treatment. Computer-generated movies of intestinal diseases and rectal examinations were used in combination with specific clinical values that are used to determine the need for surgery in horses with colic.
A world-renowned expert in colic, White has authored several books on the topic, including Equine Acute Abdomen, and Handbook of Equine Colic, as well as the surgical texts Current Techniques in Equine Surgery and Lameness and Current Practice of Equine Surgery. White is a former director-at-large for AAEP and is currently chair of the AAEP Foundation Advisory Committee. He is also a past president of the American College of Veterinary Surgeons (ACVS) and has served as director of the ACVS Veterinary Symposium since 1997.
The Marion duPont Scott Equine Medical Center is a Leesburg, VA–based full-service equine hospital that is owned by Virginia Tech and operated as one of three campuses that constitute the Virginia–Maryland Regional College of Veterinary Medicine.
This story can be found on the Virginia Tech News website: http://www.vtnews.vt.edu/story.php?relyear=2006&itemno=XXX
Contact: Marjorie Musick, mzmusick@vt.edu, (703) 771-6881
New Procedure to Correct Equine Heart Rhythm Problem
by: Emmy Widman Washington State University College of Veterinary Medicine
Recently the WSU equine internal medicine and cardiology team was trained to perform a new technique designed to help horses with an abnormal heart rhythm. The procedure, called electrical cardioversion, delivers an electrical shock internally to a horse's heart to convert the abnormal heart rhythm back to normal.
“This is a new service we are offering,” said Dr. Debra Sellon, a WSU professor and board-certified veterinarian in equine internal medicine. “It is used for horses with a condition called atrial fibrillation, one of the most common abnormal heart rhythm problems in horses. It is especially common in large breed horses like Thoroughbreds, warm blood horses, and draft breeds.
“It is a situation in which the top two chambers of the horse's heart, the atria, have an abnormal rhythm, but the bottom chambers, the ventricles, are still working like normal,” she said. “Our goal is to get the top two chambers to synchronize with the others.”
To perform an electrical cardioversion, a regular defibrillator and specially made heart catheters are used. The catheters are placed via the jugular vein. One catheter extends into the right atrium and another passes through the right atrium into the large arteries that exit into the lungs.
At the beginning of the procedure, the catheters are placed while the horse is standing, and then it is anesthetized.
“We take chest x-rays to make sure the catheters are placed correctly,” Dr. Sellon said. “When everything looks good, we connect the catheter to the defibrillator equipment and deliver a fairly low-energy shock. If that does not work, we gradually increase the energy the defibrillator delivers until the heart rhythm converts to normal or we reach a maximum acceptable level. If the conversion attempts fail, we can wait a week and try again.”
In all, the treatment generally takes 1 or 2 hours. The horse is usually under anesthesia for less than an hour of that time.
The WSU equine internal medicine and cardiology team learned to perform electrical cardioversions from Dr. Kim McGurrin of the University of Guelph's Ontario Veterinary College in September. Dr. McGurrin developed the procedure at that university and has successfully treated scores of horses herself. She has traveled to numerous universities and private veterinary practices to train veterinary specialists to perform the procedure.
“Dr. McGurrin has not experienced any severe complications in the numerous horses that she has treated, and all but two horses had their heart converted back to a normal rhythm,” Dr. Sellon said. “Sometimes a horse's heart won't convert on the first try, but usually does on the second.”
The procedure is a welcome alternative to traditional medical therapy with quinidine salts. For some horses, the medication had severe undesirable side effects, and it did not always work. Previous to electrical cardioversions, it was the only treatment option available for horses with atrial fibrillation.
Most horses that undergo an electrical cardioversion retain their normal heart rhythm after the procedure. “Approximately 15% to 20% of horses will revert to an abnormal heart rhythm, but that relapse rate is also the same for horses treated with quinidine,” Dr. Sellon said.
An additional benefit of electrical cardioversions is that horses recover faster and can return to their normal training schedule faster than those that were treated with quinidine.
Signs of atrial fibrillation in athletic horses emerge quickly after onset. These horses will not be able to run as fast or compete to their full potential. Because of these problems, most horses with atrial fibrillation are examined soon after onset of the problem and a diagnosis is made. Non-athletic horses may go longer before an owner notices a problem and often a veterinarian discovers the abnormal rhythm in a routine checkup.
Horses referred to WSU for electrical cardioversion treatment generally stay in the veterinary teaching hospital 2 days before the procedure. During that time, the horse's heart rate and rhythm are monitored and attending veterinarians obtain blood work and perform a physical and complete cardiac evaluation. After the procedure, the horse remains in the hospital for 2 days.
“The WSU Veterinary Teaching Hospital is an ideal place to have this procedure done because we have the equipment and the combination of expertise between our internists, cardiologists, radiologists, and anesthesiologists,” Dr. Sellon said.
For more information about electrical cardioversion treatment, contact the WSU Veterinary Teaching Hospital at 509-335-0711, or Dr. Debra Sellon at 509-335-0733 or dsellon@vetmed.wsu.edu.
Reprinted from: Equine News, Winter 2007, Vol. 4, Number 1, Washington State University College of Veterinary Medicine
Texas Horse Owners Urged to Implement Best Management Practices to Prevent Equine Viral Arteritis (EVA)
Texas equine producers, veterinarians, and livestock health officials have become increasingly concerned about equine viral arteritis (EVA), which has been detected in New Mexico and Utah this year. A viral disease of horses, donkeys, and other equine animals, EVA causes mares to abort, can cause mild to severe respiratory disease in some horses, and also may cause some stallions to become chronically infected and shed the virus in semen. Although EVA has been encountered rarely and is not a reportable disease in Texas, regulations have been implemented in some states, including Kentucky, New York, and Colorado.
Although some infected equine exhibit no signs of disease, owners should be alert and notify their accredited private veterinary practitioner if horses or foals develop signs of EVA, including fever, depression, diarrhea, coughing or nasal discharge, or swelling of the legs, body, or head. Laboratory testing is necessary to confirm a diagnosis, because other equine diseases can present similar clinical signs.
“EVA is not currently a reportable disease in Texas,” said Dr. Bob Hillman, Texas' state veterinarian and head of the Texas Animal Health Commission (TAHC), the state's livestock and poultry health regulatory agency. “However, we urge veterinarians and horse owners to report suspected and confirmed cases of EVA to the TAHC to ensure we have the most accurate picture of the disease in the state and can provide up-to-date information to veterinarians and equine owners.”
Horses can be infected by inhaling the equine arteritis virus, through natural service of a mare by a carrier stallion, artificial insemination of a mare with semen from a carrier stallion, or by being exposed to bedding or other objects contaminated with the virus. Stallions that shed the equine arteritis virus in their semen can infect unvaccinated mares, causing respiratory disease and abortion. Acutely infected horses spread the infection to other horses via the respiratory route. A pregnant mare also may be infected through contact with acutely infected horses and may abort. Cleaning and disinfection of stalls, trailers, and equipment can reduce the risk of EVA exposure.
“Know the EVA status of stallions, semen shipments, and mares before they are introduced onto your farm. Consult your accredited private veterinary practitioner about vaccination protocols for brood mares, stallions, and colt foals, and ensure that good biosecurity measures are followed,” said Dr. Hillman.
“If you are shipping breeding horses out of state, check to determine the entry requirements of the receiving state and allow time to comply with any testing, vaccination, or isolation requirements. Many breeding farms have implemented ‘best management’ practices, testing, and vaccination procedures to prevent the introduction or spread of EVA. Before delivering mares to farms for breeding, owners should contact the facility managers to determine what testing and vaccination procedures must be met.”
“Although only supportive treatment can be provided, most affected mares, geldings, or sexually immature stallions will eliminate the virus and recover,” said Dr. Hillman. “Sexually mature stallions, however, can become carriers of the disease and shed the virus for long periods. Shedding stallions should be isolated and bred only to vaccinated mares.”
“It is very important to have breeding horses tested, and if appropriate, vaccinated before the breeding season. After vaccination, stallions and mares should be withheld from breeding for at least 28 or 21 days, respectively. Vaccinated horses also must be maintained away from pregnant mares for at least 28 days,” he said. “EVA vaccine may be acquired only by veterinarians, with prior TAHC approval.”
Additionally, mares vaccinated for the first time and bred to a carrier stallion should be isolated from other equine for 21 days after breeding. Owners of breeding horses considering vaccination should consult their veterinarians if the horse may also be shipped in interstate or international commerce. A specific pre-vaccination protocol to assure the horse was test-negative before vaccination may be required, because vaccinated horses will test positive for the disease.
“Several horse breeders and a number of equine veterinarians have contacted the TAHC about EVA and to urge Texas equine producers to take all necessary precautions to prevent establishing EVA in Texas horses,” said Dr. Hillman. “Equine producers and veterinarians believe this disease can be handled through judicious application of best management and biosecurity practices, coupled with appropriate use of testing and vaccination of breeding animals.”
“The current EVA situation will be reported to TAHC commissioners at their meeting Tuesday, December 5, in Austin,” he said. “Development of EVA rules is not anticipated at this time. Horse breeders are urged to work with their veterinarians to institute best management and biosecurity practices immediately to protect their investment and the health of their animals. EVA can be prevented and controlled by sound management practices and selective use of the EVA vaccine.”
Links to additional information about EVA may be accessed at TAHC's website at http://www.tahc.state.tx.us.
Reprinted from: AAEP myHorseMatters.com (url: http://www.xcodesign.com/aaep/displayArticles.cfm?ID=299)
Contact: Texas Animal Health Commission, Box 12966, Austin, TX 78711, 800-550-8242; fax 512-719-0719
Bob Hillman, DVM, Executive Director, For info, contact Carla Everett, information officer, at 1-800-550-8242, ext. 710, or ceverett@tahc.state.tx.us
Current Treatments for Equine Protozoal Myeloencephalitis
Equine Protozoal Myeloencephalitis (EPM) is one of the most common treatable neurologic diseases of American horses and is caused by the apicomplexan protozoan Sarcocystis neurona. This protozoan penetrates the central nervous system, producing varying levels of neurologic disease. In parts of the United States virtually all horses are exposed, with a small proportion (<0.5%) exhibiting neurologic symptoms. Because S. neurona can locate anywhere in the brain and spinal cord, the disease can mimic any neurologic condition, and diagnosis can be challenging. EPM was first identified in the 1960s, with development of improved diagnostic tests in the 1990s. Since 2000, three Food and Drug Administration (FDA)—approved treatments for EPM have been brought to market.
Treatment of EPM is challenging because S. neurona is an intracellular parasite and an expert in avoiding immune system attack. The three different anti-protozoal treatment modalities currently available work on entirely different pharmacologic principles.
Traditionally, EPM was treated with combinations of pyrimethamine and a sulfonamide, one of the so-called “potentiated sulfonamides” used in classic anti-malarial therapy. These drugs act “in sequence” on nucleic acid synthesis. The sulfonamide directly inhibits the incorporation of para-amino benzoic acid (PABA) into folic acid, and pyrimethamine selectively inhibits dihydrofolate reductase. When present together in the brain at effective concentrations, these drugs produce a 1 to >2 synergistic inhibition of nucleic acid metabolism. This combination was, for many years, the only known treatment for EPM, although the duration of treatment was often prolonged. Potentiated sulfonamide combinations have long been marketed by compounding pharmacies, and more recently, Phoenix Laboratories has brought to market an FDA-approved formulation of pyrimethamine and sulfadiazine, marketed as ReBalance.
Side effects that may be associated with pyrimethamine–sulfonamide combinations are related to inhibition of host nucleic acid metabolism. Animals on potentiated sulfonamide treatments should optimally be monitored for inhibition of red cell formation, leukopenia, and thrombocytopenia. Some of the earlier potentiated sulfonamide preparations were associated with reports of reduced spermatogenesis in stallions.
Another treatment, Marquis (ponazuril), is adapted from a widely used poultry coccidiostat, toltrazuril. These drugs act by directly attacking the “apicoplast” organelle of S. neurona. Apicoplasts are chloroplast-related organelles that were acquired by S. neurona millions of years ago. They are highly susceptible to specific attack by herbicide-related drugs such as ponazuril. Working with these drugs, University of Kentucky researchers showed that they are highly specific and effective treatments for EPM. Ponazuril is well absorbed orally, has a 4.5-day plasma half-life, and is virtually nontoxic to equines at clinically effective doses. Single daily dosing is effective, and in an extensive field study, no adverse responses could be linked to treatment.
The manufacturer's suggested treatment period is 28 days. Because of its unique mechanism of action, Marquist is essentially specific for apicomplexans, and a positive response to treatment offers strong support for an EPM diagnosis. Marketed in 2001, Marquist was the first FDA-approved treatment for EPM.
Nitazoxanide (Navigator) is in a novel class of anti-infective drugs and is thought to act by inhibiting pyruvate-ferredoxin oxidoreductase in susceptible organisms. It has a broad spectrum of action, acting on enteric bacteria, protozoa, and viruses. In human medicine it has been approved as a broad-spectrum anthelmintic and anti-viral drug.
The oral dose is carefully calculated, and treatment starts at a half-daily dose for the first 5 days, increasing to the full dose of 22 mg/kg for the remaining 23 days. The principal adverse response in the horse relates to the drug's broad enteric action, which can change equine intestinal flora and produce enteric problems. The addition of rice bran or corn oil to the diet helps to reduce the incidence of intestinal problems.
Horses on any long-term therapy for EPM should be monitored daily for adverse reactions and changes in clinical signs.
Numerous adjunctive therapies for EPM are also used. Anti-inflammatory therapy can help reduce inflammatory responses to the protozoan and may be useful in “treatment crisis” (transient worsening of clinical signs early in treatment) reported in some severe cases receiving an anti-protozoal medication. Use of corticosteroids in EPM cases is controversial among veterinarians.
Immune stimulants have also been recommended and include products such as Propionibacterium acnes administration, mycobacterial cell wall extracts, oral levamisole, and alpha-interferon. Additionally, a commercially available chemically inactivated vaccine of merozoites of S. neurona with an adjuvant has been suggested to further stimulate cell-mediated immunity.
Clinical experience suggests that rehabilitation is facilitated by mild to moderate unmounted, controlled exercise. The exercise level is dictated by the stability of the horse and the opinions of both the examining veterinarian and the owner. Complete recovery (to neurologic normalcy) may not be possible, but rehabilitation and strengthening of affected horses can maximize the clinical outcome.
Based on contributions by David Granstrom, Dan Howe, Brad Bentz, Levent Dirikolu, and Thomas Tobin at the Maxwell H. Gluck Equine Research Center.
Reprinted from: Equine Disease Quarterly, Vol. 16, Number 1, January 2007 http://www.ca.uky.edu/gluck/q_jan07.asp#EPM
Contact: Dr. Thomas Tobin, Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY, 859-257-4757, ttobin@uky.edu
Reproduction: An Emerging Focus at North Carolina State
by: Christy West, TheHorse.com January 2007, Article #8566
Many of the United States' leading equine reproduction research institutions, such as Colorado State University, the University of Idaho, Utah State University, and Texas A&M University, are located in the western half of the country. However, North Carolina State University is working to make sure horse owners in the eastern half of the country have the same caliber of reproductive research and services available nearby.
Says Carlos Pinto, DVM, PhD, Dipl. ACT, assistant professor of theriogenology, “North Carolina has traditionally not been well known for equine reproduction research. When I came here 4 years ago, I was charged to try to do more. The most important initiative was creating the satellite repro clinic at Southern Pines (formerly called the Veterinary Equine Research Center, now termed the Equine Health Center, 62 miles from the Raleigh college). 2004 was our first breeding season there; we started small, but our caseload tripled in 2006 from last season. And now we do more than 100 semen collections per year for clinical, teaching, and research purposes.”
The 83-acre Equine Health Center (which also offers ophthalmology, podiatry, and lameness diagnostic services) has reproductive clinicians (board-certified theriogenologists) at the facility at least 3 days per week, and their services include more than just basic examinations, palpations, and inseminations. Southern Pines' many paddocks and laid-back atmosphere are home to approximately 20 broodmares available as surrogate mothers in the clinical embryo transfer program. Oocyte transfer and gamete intrafallopian transfer are also on the menu of services offered at NC State.
Working on client horses is important at both clinics, but research to better understand equine reproduction and find more effective ways of assisting reproduction is a major focus.
Recent Research
The following studies done at NC State were all presented at the 9th International Symposium on Equine Reproduction in Kerkrade, The Netherlands, in August 2006, and published in Animal Reproduction Science (volume 94).
Semen Vials to Replace Straws?
One simple concept has found great practical success at NC State—using 3.6-ml plastic semen vials rather than 0.5-ml or 1-ml straws to store semen. The shorter, fatter vials are much easier to use and they provide nearly 3 times as much semen storage volume in a tank as straws, says Pinto.
“Semen quality is almost the same; motility is slightly lower, but the breeding dose is way above the minimum we need, and the vials are much easier to work with before and during freezing,” he explains. “Rather than using multiple straws (to get one full breeding dose), you just use the one and unscrew the top (instead of dealing with plugged straws).”
He also noted that the slightly lowered motility might be improved with variations in freezing protocols, which were designed for straws, not vials.
Detecting Progesterone Hormone in Mares with a Canine Assay
“It's hard to find kits to detect progesterone levels in mares (this helps determine whether the mare is in the luteal phase of her estrous cycle; if she is not, she is ready for breeding),” says Pinto. Pointing to a photo of a progesterone assay kit, he comments, “This one's designed for dogs (Ovucheck's Premate 10) and we validated its use for horses.” He reported an overall accuracy of 98.8% for the test's ability to report high (more than 3 ng/ml) versus low (less than 3 ng/ml) progesterone levels in mares.
Synbiotics, the company that manufactures the Premate 10, is working on an equine version of the test for field and clinic use, but they do not yet have an estimated date of availability.
Pinto notes that determining progesterone levels might have many different applications depending on the reproductive status of the mare. He gave the following examples:
Investigating Stallion Fertility
This study “looked at a sperm membrane protein (SP22) to see whether there was any variation in its concentration across seasons,” Pinto explains. “We don't know exactly what this protein controls, but in rats we know that if you block the protein, you affect fertility. Results of previous studies headed by Dr. Gary Klinefelter (a research biologist at the U.S. Environmental Protection Agency), a collaborator in the current equine study, indicate that it has a pivotal role in fertilization and is thus a biomarker of sperm quality.”
The study found that this protein tends to be higher for spermatozoa collected in the fall (which represent sperm cells produced during summer, a period of peak testicular function). Analysis of spermatozoa collected during winter and spring are currently underway, and preliminary results point to a seasonal expression of the protein SP22. He suggested that this protein could serve as a marker of fertility with more research.
Prostaglandin Dosage
Another study evaluated various dosages of a commercial brand of prostaglandin F2alpha (Lutalyse) to cause mares to short cycle. The study dosages ranged from the recommended dose of 2 cc down to one-eighth of that—0.25 cc administered in the muscle.
“This work has been done before, but what has not been done before is to see how normal the next cycle is (as assessed by ultrasonography of the ovaries and uterus),” says Pinto. “Some people say, ‘I don't want to induce changes in my mare, I want a normal cycle.’ Well, it is a normal cycle. The results of our study showed that the reproductive cycles induced by prostaglandins were characterized by normal follicular dynamics, follicle size, rate of growth, and ovulation pattern.”
“Some of these studies are simple, but that's good for two things—they get students' interest engaged, and make it easier for horse breeders to understand what you've learned,” he comments. “Many of current studies are performed in great part by veterinary students with special interest in research and by those participating in summer research internships.”
Ongoing Research
Embryo Transfer Timing
Normally, an embryo donor mare is flushed at day 7 or 8 post-breeding; at that age, embryos are often too small to see in the mare with ultrasound. Pinto has approximately 3 years of data from holding off until later. “I was waiting for an embryo to be visible (on ultrasound) at about 9.5 to 10 days,” he says. “At that stage, they are about 3 cm, and that is about as small as I can see them. So this is like pregnancy checking a mare and only flushing her if you see an embryo and can confirm that she is pregnant. And then when you transfer it into another mare, you can see if it was successful.” Pregnancy rates are about 30%, compared with 50% to 60% at the end of the season with smaller embryos, he notes. He has gotten a live foal from this schedule as well.
However, there are drawbacks: “It is not ready to be applied yet, because it is hard to manipulate those large embryos,” he adds. “We do not have a tool designed to handle and manipulate them. We hope to have in the near future an ultrasound machine that will enable us to identify these embryos at 1.5 to 2.5 mm in diameter; that would help with research and maybe clinical application, as you have better success manipulating smaller embryos.”
Future Plans
Pinto says his main goal is to build a program at NC State that aims not only for excellence at clinical reproductive services, but also to train high-qualified veterinary specialists through intense teaching and participation in clinical research studies, such as summer research projects. “It is an excellent chance to train veterinary students in special procedures while translating the importance of scientific investigation and its application to clinics,” he comments.
As far as upcoming clinical services, Pinto says intracytoplasmic sperm injection (ICSI) will soon be offered for clients. He is targeting the 2008 breeding season for 2009 foals. In keeping with NC State's goal of becoming a premier equine reproductive service provider, he adds, “Only a small percentage of breeders utilize it, but if anyone should offer it, it should be a tertiary care center like us that has the mission to teach and train future veterinary specialists.”
For more information see www.vet-equine.com.
Reprinted with permission of The Horse; visit www.TheHorse.com for more horse health news.
PII: S0737-0806(07)00082-2
doi:10.1016/j.jevs.2007.02.005