WEVA: On the Move
They met in Italy to exchange information about reproduction, sports medicine, infectious diseases, transportation, and surgery. The more than 300 delegates from 29 different countries, including Germany, Australia, New Zealand, Ireland, Denmark, the United Kingdom, and the United States, heard topics addressed in Italian and English. With so many different topics and time zones represented, it was not surprising that the common language was equine.
At the fifth congress of the World Equine Veterinary Association (WEVA), one slide put before the group by Marianne Sloet of Utrecht University in the Netherlands was demonstrative of how much there is in common among horses around the world, even if the languages and terminology sometimes are a bit different. In talking about common skin diseases, she showed a picture of a horse's white fetlock with what we in the United States would call dew poisoning. Around this one photo were about 10 different names used throughout the world for this one disease.
Some of the problems addressed at WEVA were of concern only in specific parts of the world, such as grass sickness, but for the most part, it was amazing how similar the basic diseases and problems are among horses.
This year's conference was organized by Prof. Roberto Busetto and others from the Italian veterinary association. Peter Timoney, FRCVS, PhD, president of the WEVA and director of the Gluck Equine Research Center in Kentucky, said this year's congress was, "The most successful conference we've had."
It was appropriate that Timoney opened the scientific sessions with a topic entitled Emergent and Resurgent Equine Infectious Diseases: A Global Perspective. He noted that there are at least seven new known diseases that have emerged since 1970 throughout the world, including Potomac horse fever in the United States, CEM in the United Kingdom, Getah virus in Japan, and acute equine respiratory syndrome in Australia. Diseases that are considered resurgent, or are appearing again after a time of not causing problems, include several epidemics and outbreaks of Venezuelan equine encephalitis, equine herpes virus, equine infectious anemia, and equine viral arteritis.
Also, there have been new biotypes of recognized pathogens that have sprung up throughout the world, including new strains of influenza and a new type of the VEE virus (1E).
These diseases have a critical influence on trade, especially since the demise of the previously used "zero risk" policy. That policy allowed a country to refuse admittance to any horses from a country just because "those people" had a disease "you" didn't. That restrictiveness is no longer possible under the new world trade agreements. Timoney noted that import control policies should represent a compromise between facilitation of trade and providing adequate safeguards against introduction of certain equine diseases into the importing country.
Some diseases that are considered "notifiable" are listed with the OIE (Office Internationale Epizootic), which is the world organization that monitors and offers guidelines on infectious and contagious diseases in all species of animals. The goal of the OIE is to prevent the spread of contagious diseases and facilitate international trade in animals and animal products (such as semen and embryos). Equine diseases that are "non-notifiable" are tracked through the International Collating Center in Newmarket.
Having information about equine outbreaks and status of diseases is of critical importance in controlling and preventing the spread of these diseases. Timoney called for accurate, up-to-date information on occurrences of diseases throughout the world. He said with that knowledge would come the ability to minimize restrictions on free movement of horses between countries and maximize the protection of horse populations from the introduction of an exotic (non-native) disease.
"With the trend toward increasing movement of horses and the emergence and resurgence of diseases, we need more effective mechanisms of getting information collected and disseminated," said Timoney. "We need to get a permanent working group for equids in OIE. That is needed for regulations and the frequent addressing of international diseases and movement of horses." Currently, equine problems are discussed under the auspices of the exotic animals working group in OIE.
The question was raised about why OIE did not want to establish or reactivate a working group on equids. Timoney said he feels the OIE will only respond with pressure from different continents so that the controlling group realizes that equids are of global interest.
In response to the comment that all five equine-producing continents were represented in that room and what could they do to advance this cause, Timoney said, "I recommend that regular representatives of OIE be made aware of the concerns of the equine industry and that you bring political pressure to bear on those delegates."
In discussing why infectious diseases are an impediment to international transportation of horses, Timoney noted the increase in just the last five years in the number of prestigious equine events throughout the world, the increasing number of stallions breeding mares in both the Northern and Southern hemispheres, and the increasing acceptance of shipped semen and embryos. He cited two examples of how infectious diseases can cross international barriers and become problems in "naive" or unprotected populations of horses.
Contagious equine metritis (CEM) was introduced into the United States from England and Ireland in 1977, said Timoney. At that time, it was a previously undescribed venereal disease. It had the potential to cause wide-spread problems in mares, and stallions and mares could become carriers. From 1977 to 1997, a total of 25 countries have reported problems with CEM.
Equine viral arteritis (EVA) can cause abortion in mares and a long-term carrier state in the stallion, noted Timoney in his second example. (The carrier rate in stallions can range from 22-50% of infected horses.) In Italy, an eradication program has been put in place to eliminate EVA in the stallion population. Italian veterinarian G. I. Autorino reported that shedding stallions were not permitted to breed, and there currently are only eight shedding stallions (of all breeds) identified in Italy, down from 40 when the program started in 1995.
Timoney noted in response to a question from the audience on age relationship to sickness in foals that he had found that congenital acquisition (present at birth) of the arteritis virus usually resulted in the death of the foal.
In the question and answer period following the first session, the question was raised about the variety of new diseases and new strains of old diseases currently infecting horses throughout the world. Timoney called for vaccine manufacturers to include new strains of diseases--such as influenza-- into vaccinations currently being sold.
Information on rotavirus in foals and the new vaccine produced by Fort Dodge Laboratories garnered attention, even though the vaccine is not available in Europe at this time. The only state in the United States that has not requested a conditional license for use of the vaccine in pregnant mares is Alaska (see The Horse of March 1996, page 27). Roberta Dwyer, DVM, Dipl. ACVPM, of the Gluck Equine Research Center, reported on the vaccine, as well as management techniques used to control introduction or spread of the disease, which is a problem worldwide.
Veterinarian C. E. Kerber of the University of San Paolo, Brazil, spoke on the control of equine piroplasmosis in endemic countries. This is the tick-borne disease that caused the furor prior to the 1996 Olympic Games in Georgia (see special report in The Horse of April 1996). This disease is native to most countries throughout the world, with the exception of the United States, Canada, England, Ireland, Japan, and Australia. Kerber reported that it is possible to decrease substantially the number of positive horses by controlling the tick populations in the environment.
Fort Dodge Animal Health, a major sponsor of the WEVA congress, presented a session on moxidectin, introducing the new European version of the drug named Equest (which is named Quest in North America). There were multiple international presentations explaining the efficacy of the drug and how it compares to ivermectin in trials on horses in the United States, Italy, Belgium, and France.
In his study of road transportation on water and electrolyte balance of conditioned horses, J. S. Van den Berg of the University of Pretoria, South Africa, surmised that transportation affected water and electrolyte balance of conditioned horses for up to six hours after traveling. In his study, six Thoroughbred fillies were conditioned using a treadmill, then were fitted with urine collection devices and loaded for transportation. They were offered free-choice water and hay, and the intake was measured. However, none of the fillies drank while being transported for eight hours. A control group that was not transported also was studied.
Following transportation, the fillies were found to have lost an average of 3% of their body weight. All the fillies drank and ate hay in the six hours they were studied after transportation, and it was noted that they regained their pre-transportation weight within one hour of being transported because of drinking more water than controls following transport.
Van den Berg noted that there were significant differences in urine and feces secretions of various minerals between those fillies which were transported and ones in the control group. He also noted that in the recovery period, transported horses drank almost twice as much as control horses, and ate less hay.
M. H. Atock, an international shipping agent based in the United Kingdom, said plans were already underway for the shipment of horses from around the world to the 2000 Olympics in Sydney, Australia. While there still are decisions to be finalized, such as if there will be restrictions because of piroplasmosis, he said Australia is working to simplify import regulations, which currently require a two-week pre-export quarantine in an accepted country and a two-week post-travel quarantine in Australia. Atock also noted that a booster for equine influenza will be required before travel since Australia is considered free of that disease.
Barry A. Ball, DVM, PhD, Diplomate American College of Theriogenologists, is a professor and holder of the Hughes Endowed Chair of Equine Reproduction at the University of California School of Veterinary Medicine. He was recognized at the 1997 WEVA Congress with the Schering Plough Animal Health award in reproduction. His paper at WEVA detailed ongoing research on the formation of a functional sperm reservoir in the equine oviduct.
After sperm are released into the female reproductive system, they don't immediately go to fertilize the egg. Instead, it has been learned that sperm attach to the oviductal epithelium, where they remain viable for up to seven days. The ability of sperm to adhere to the oviduct could be related to stallion fertility, Ball noted.
There seems to be an influence on the sperm by the oviduct, and an influence on the oviduct by the sperm. The oviduct is thought to play a key role in sperm capacitation. Freshly ejaculated spermatozoa (from any mammal) are unable to fertilize oocytes without undergoing certain changes. This series of changes has been termed capacitation. It is thought that chemicals secreted by the oviduct aid in this process. The ability of the sperm to attach to the oviduct could be a limiting factor in fertility of the stallion or mare. (More on this topic from Ball will be presented next spring in The Horse.)
Angus O. McKinnon, BVSc, of Goulburn Valley Equine Hospital in Australia, keeps a research herd of about 75 mares which also are used for embryo transfer. Plus, his group manages some 2,000 Thoroughbred and Standardbred mares. He said the most difficult part of embryo transfer is management of the recipient herd.
"We biopsy and maintain the herd year-round," said McKinnon, adding that owners would much rather sell mares to him for recipient use than for slaughter, which makes it easier to obtain a sufficient number of mares.
"Many veterinarians in Australia collect embryos and send them to us," he said.
The Goulburn facility has about a 75-80% pregnancy rate using non-surgical transfer of embryos, "but I strongly believe that the surgical transfer is better," added McKinnon.
He has devised a catch system for his recipient mares that allows him to ultrasound 20 or more mares an hour. And the surgical transfer process has been fine-tuned to take 20-25 minutes from tranquilization to the last stitch.
The recipient mares he uses have been ovariectomized (removal of the ovaries) through vaginal surgery. He said this operation makes it easier to regulate the recipient mares so that he only needs one recipient mare for each donor mare, rather than the herd of two to one (recipient to donor) that is kept at many facilities. The pregnant mares then are maintained on daily Regumate.
One day can make a big difference in shipping embryos. He said while it is easier to collect an egg seven days after ovulation rather than six days after ovulation, it is more difficult to ship and transplant the seven-day eggs successfully. He estimated that they expect a nearly 100% pregnancy rate with six-day eggs, compared to a 70% pregnancy rate with seven-day eggs. The transfer of 10-day-old embryos only resulted in pregnancy rates of 10-12%.
McKinnon said he sees a "huge future" for getting an egg, injecting one sperm, then placing the fertilized egg into a recipient mare. This technique would allow stallions to breed many more mares, and could assist stallions with fertility problems.
In addressing the problem of early embryonic death, McKinnon said in his opinion, this is seen more in horses than cattle. "If we started culling poor breeders, then we could improve on that," he said. "But we want to produce an elite athletic horse," so breeding ability is not sought after in considering matings.
McKinnon said he also feels the closer a mare is bred to foaling, the more chance she has of suffering early embryonic death, especially if she was bred on her foal heat. He noted that advanced age also increases the possibility of early embryonic death.
In a study that included about 1,000 mares in various artificial insemination centers in Germany, it was determined that there was a group of mares which would show estrus for about seven days with a large follicle (40 mm in diameter or larger), then would stop showing signs without ovulating. These follicles, scientifically called anovulatoric follicles, would remain for up to eight weeks, but would not get "soft" like a pre-ovulatory follicle.
Researchers punctured the follicles and aspirated the fluid in a group of 17 of these mares. It was found that all the treated mares showed normal estrus and behavior following estrus, and 11 of the 17 became pregnant. Therefore, the researchers felt that in some cases, follicle puncture could be used as a therapy to shorten the time of diestrus in this type of mare.
Uterine Fluid And Frozen Semen
It has been well-documented that mares have an acute uterine inflammatory response post-breeding that includes the production of uterine fluid. However, little has been studied in mares inseminated with frozen semen.
Jonathan Pycock, BVetMed, PhD, DESM, MRCVS, who is a diplomate in equine stud medicine and a specialist in equine reproduction in England, utilized a group of 59 mares to study this problem. The mares were examined and cultured prior to breeding, with 21 of the mares showing minimal fluid in the uterus. The mares then were inseminated with frozen semen from one of five stallions. Mares were treated with uterine lavage, oxytocin, and intrauterine antibiotics 12 hours after insemination. It was found that 80% of mares had fluid detected 12 hours after insemination. By 24 hours, 38% of the mares still had fluid accumulation. At 48 hours post-insemination, only two of the mares still had fluid detectable in the uterus.
"There appeared to be no relationship between fluid production and volume of inseminate within the small range of insemination volumes used in this study," said Pycock, who added that mares with fluid persisting longer than 24-48 hours usually had reduced pregnancy rates.
Foal Heat Pregnancy Rates
Professor F. Camillo of the University of Pisa in Italy noted in studying 501 rotting mares in Italy from 1990-95, there was no difference in fertility when breeding on foal heat versus other cycles. In looking at 279 post-partum mares versus 221 non-lactating mares, when bred with artificial insemination using fresh semen, the foaling rate was not statistically different. Therefore, he determined that mares should be bred at foal heat unless foaling complications require a delay.
Professor Reuben Rose, DVSc,PhD, Dip. Vet AN, FRCVS, of the University of Sydney in Australia discussed a study of 149 horses comparing the different grades of laryngeal function as assessed by endoscopy at rest and measurements of gas exchange and exercise capacity during a standardized treadmill test.
His data suggested that endoscopic examination of laryngeal function at rest using a simple grading system provides an indication of dynamic changes in ventilation and the effects on gas exchange during exercise. The study indicated that horses which have some movement of the left arytenoid cartilage but are unable to achieve full abduction have similar ventilatory effects and blood gas responses during maximal exercise to those with complete paralysis. He also noted that some horses with a grade 3 laryngeal function at rest had blood gas results similar to those of horses with grade 4 and 5 laryngeal function, indicating that discrepancies might occur between the resting assessment of laryngeal function and laryngeal function during strenuous exercise.
Lower Airway Disorders
Pierre Lekeux, head of the Centre for Equine Studies at the Animal Health Trust in England, and head of the Equine Sports Medicine Center in Liege, Belgium, said control of subclinical lower airway disorders is a major challenge to veterinarians, owners, and trainers. The risk factors that can contribute to lower airway disorders include exercise, which causes increased blood and air flow through the lung, with high transmural pressures and stresses on the alveolear-capillary membranes; deep inhalation of dust particles while at exercise; stresses on the immune system; and environmental microorganisms such as air pollutants and weather.
Control of lower airway disorders can be assisted by modifying the environment for better health of the horse, modulating inflammation, correction of functional disorders, and suppressing the causes of disease. He went on to discuss in-depth the various tools veterinarians have to fight these causes of disease. The tools included anti-oxidants, a field he said needed more work for use in equines.
"Absent a diagnosis, medicine is poison and surgery is trauma," noted Kent Allen, DVM, on a slide that led into his discussion of thermal imaging as a diagnostic. He said that the 1996 Olympics saw a rebirth of thermal imaging because of the use of the modality as a diagnostic.
The equine hospital at the Olympic vendue in Georgia was the best-equipped in the history of the games. He said thermal imaging was the single most requested technology at the Olympics, because it focused on diagnosis before there was a problem. He said many teams would screen horses with thermography before using scintigraphy. Knowledge of how to use the equipment, and what indicates a problem, are key to successful thermal imaging, noted Allen.
Cosequin In Navicular Cases
The first placebo-controlled, double-blind clinical trial of the use of Cosequin as a treatment for navicular syndrome showed there was improvement in the signs from a clinical standpoint. R. Reid Hanson of Auburn University said horses used in the study had navicular problems less than one year, and were from five to 15 years old. Clinicians evaluated the horses before the trials began, and at days 28 and 56 into the study, without knowing which group was treated and which was control. Owners of the horses evaluated the animals weekly, again without knowledge of which horses were treated. Study horses were given nine grams of Cosequin twice a day for 56 days.
Clinicians noted an improvement in scores for 59% of horses, versus improvement in 1.4% of horses receiving a placebo. Owners noticed improvement in 43% of horses treated, and a decline in horses receiving a placebo. Hanson therefore suggested that the clinical trial of Cosequin use in horses with navicular syndrome confirmed anecdotal reports of improvement or maintenance of soundness.
While this has been an overview of some of the topics presented during the WEVA Congress, the true value of the meeting was the exchange of information, and fellowship, of the top-level researchers and veterinarians from around the world. Other articles will appear in upcoming months to expound on these and other items of interest from the WEVA meeting. The next Congress will be held in Paris in 1999.
About the Author
Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.