A World on the Move
The World Equine Veterinary Association (WEVA) met in Sorrento, Italy, in conjunction with the October 2001 Italian veterinary association annual meeting. WEVA meets every other year in locations designed to attract veterinarians from countries that don't have readily accessible continuing education programs. The goal of WEVA and the host veterinary association is to disseminate veterinary information and technology to these veterinarians.
Many topics were covered by an array of international speakers. While the terrorist attacks on the United States were fresh in the news, the emphasis at this convention was on free exchange of information and camaraderie.
Following is some of the information presented at the 2001 WEVA Congress.
Old Maiden Mare Syndrome
Reproduction specialist Jonathan Pycock, BVetMed, PhD, DESM, MRCVS, a specialist in equine reproduction, said there is a big difference between maiden Thoroughbred mares which are retired from the racetrack at ages four to six for breeding and performance mares which finish a show career at 13-14 years of age, and are then bred.
Pycock reminded horse owners that no matter what age the mare, all mares exhibit a mating-induced endometritis (inflammation of the uterus) that is physiological, not pathological (caused by a disease).
"There is an inevitable transient endometritis no matter how we breed, by natural cover or AI," he said. He said that if mares didn't get this transient endometritis, it would be a bad thing. "It's there to get rid of debris from breeding. Semen itself causes inflammation."
Pycock said that most mares are resistant, or will naturally overcome post-mating endometritis, and that it usually resolves within 24-48 hours. The susceptible mare is unable to resolve endometritis within the 48-hour timeframe. That failure to resolve the inflammation and clear the debris of breeding will result in embryonic death, noted Pycock.
"About 5 1/2 days after fertilization, the fertilized egg has to move into a healthy uterus to survive," he said. "Premature release of prostaglandin due to the inflammatory process persisting causes early regression of the corpus luteum or CL (luteolysis) and brings the mare back into estrus, even if there is a fertilized egg."
He also said that all mares don't fall into two categories--resistant or susceptible.
"There's a whole range of clinical signs--some mares are very resistant, some moderately resistant, some moderately susceptible, some very susceptible. So, you can't give one treatment protocol for all mares."
What Causes the Problem?
Pycock said that failure of mechanical clearance (getting rid of the by-products of inflammation in the uterus following breeding) is the key breakdown that occurs in susceptible mares.
One cause of failure of mechanical clearance is excessive fluid production or insufficient clearance of uterine fluid due to reduced contractions of the uterine wall's muscular layer (myometrial contractions). Other causes could be insufficient lymphatic drainage, a large uterus that hangs over the pelvic brim, or a tight cervix.
"If a mare has a tight cervix, you can administer as much oxytocin (to stimulate uterine contractions) as you want, but unless you open the cervix, it won't drain." Manual dilation of the cervix in these mares often results in drainage of uterine fluid. "You have to help the mare," said Pycock.
A tight cervix can be a problem with the maiden mare, which many people presume is easy to get in foal. Veterinarians need to make owners aware that just because they have a maiden mare, it doesn't mean that getting her in foal is straightforward. (The difficulties one might face in trying to get a maiden mare in foal can include a tight cervix, poor lymphatic drainage, or poor myometrial contractions used to clear debris after breeding.)
Management of the susceptible mare involves proper hygiene at breeding, correct timing of breeding, and correct conformation of the mare's reproductive tract. Check a mare's perineal conformation--her vulval lips should be aligned and perpendicular to the ground, and when they are parted there should be no vaginal aspiration of air.
"There's no use in treating the fluid in lumen if the mare has a poor vulvar shape and is going to contaminate her uterus each time she defecates," said Pycock.
Timing of breeding is also important in getting a mare in foal. Pycock suggested using endometrial edema (swelling) to predict ovulation, as endometrial edema scores generally decline 24-36 hours before ovulation.
One rule with the susceptible maiden mare is that there might be only one chance to get her in foal before there are problems, noted Pycock. "The more you put in there (semen with other matings), the more problems she has."
Artificial insemination is very helpful with older maiden mares. Ultrasound evaluation of the uterus for detection of interlumenal fluid is important because this fluid is an indication that the mare might be "susceptible" and needs to be managed accordingly.
Treatment of Endometritis
Unlike infectious endometritis, mating-induced endometritis has a known starting point. Treatment should begin before infection/inflammation is established.
"An older approach was to treat the mare after she ovulated," said Pycock. "I say we treat the mare when we breed her. If you wait, you will allow endometritis to get out of control. There will be a sea of fluid in that uterus if you wait until she has ovulated before you treat her."
If there is uterine fluid detected before you breed the maiden mare, what should you do? Mares with uterine fluid accumulation detected during a pre-breeding exam have a reduced pregnancy rate, Pycock explained, since fluid should not be in the uterus. Therefore, if fluid is noted before breeding, appropriate therapy should be instituted to remove it.
While there is no standard approach for those mares that are susceptible to mating-induced endometritis, there are some helpful procedures that can be performed. First of all, in proestrus or early estrus, a veterinarian should do a cytological and bacteriological exam on the uterus.
During estrus, there should be daily monitoring of the ovaries/uterus and measurement of the amount of intralumenal fluid. If the diameter of the fluid image on an ultrasound scan becomes larger than 0.2 inches (0.5 cm), a veterinarian might use oxytocin twice a day. If the amount of fluid becomes larger than 0.8 inches (2.0 cm), then uterine lavage with saline and oxytocin twice a day might be done.
On the day of insemination, if there is fluid greater than 0.2 inches (0.5 cm), oxytocin might be used six hours prior to and six hours after insemination.
"I rarely use antibiotics before insemination," noted Pycock.
To manage a very susceptible mare, you should use a single mating two to three days before anticipated ovulation, said Pycock, since average stallion sperm will live 48-72 hours in the mare's reproductive tract, so it will happily keep until she ovulates.
An ultrasound exam should be performed 3 1/2 hours after mating to determine fluid accumulation. If fluid is present, intravenous oxytocin can help, followed by another ultrasound 20 minutes later. If the fluid is gone, a low volume of broad-
spectrum antibiotics can be infused into the vagina. The mare is re-examined the next day and the oxytocin administration is repeated.
"Oxytocin is cheap, easy to give, and a very safe drug," said Pycock. "In the mid-1990s, our research showed that oxytocin use post-breeding increases pregnancy rates in subfertile mares. If an owner needs to do it, he/she can give oxytocin intramuscularly (under veterinary advice) without a problem."
Oxytocin only has a half-life of 7 1/2 minutes, so its effects are short-lived; it is through the mare's system rapidly.
Lymphatic drainage is important, Pycock added. Failure of uterine clearance is not just from a myometrial defect--some mares have failure of lymphatic drainage. If during estrus a mare has a heavy, strong edema pattern, a uterine biopsy should be used to determine the health of the lymphatic system.
Lavage and Hygiene
Early post-breeding uterine lavage with saline four to six hours after breeding might be beneficial in mares with a known history of fluid accumulation.
"Performing the lavage between four and six hours after insemination does not negatively affect conception and may even benefit susceptible mares," said Pycock.
Simple management practices also can increase the pregnancy rates in these mares. Remember good hygiene. "If you use lavage, remember you must clean the mare first so as not to introduce bacteria," warned Pycock.
One study Pycock discussed contained 380 mares divided into in four groups (95 in each group). The four groups were the control group, mares given antibiotic lavage alone, mares given oxytocin alone, and mares given antibiotics and oxytocin in a combined treatment program. All treatments were given within 48 hours of mating. The per cycle pregnancy rates were as follows: control, 57%; antibiotics alone, 69%; oxytocin alone 65%; antibiotic and oxytocin 77%.
The results of this study showed the benefits of treatments that either eliminate or reduce intrauterine fluid in the management of persistent post-mating endometritis.
Management of the susceptible mare includes regular ultrasound exams of the uterus, good management, and adopting a routine post-mating treatment policy, said Pycock. But first, you must be able to identify the mare which needs post-mating treatment. History is important. The most successful cycle on which to breed an older barren mare is the first cycle on which you attempt to breed her. This might not necessarily be the first heat cycle of the year for that mare. In fact, with older mares, it is better to let the mare have at least one estrous cycle before breeding her. Then, do whatever it takes to get her in foal the first time.
Pleuropneumonia By Any Other Name
"Also known as pleuritis, travel sickness, or shipping fever, pleuropneumonia is one of the most major clinical problems vets are faced with, and one of the most expensive to treat." This statement opened a talk on the causes and treatment of this problematic respiratory disease by Warwick Bayly, BVSc, MS, PhD, Dipl. ACVIM, dean of the vet school at Washington State University. "The outcome can be based on the ability or willingness of an owner to pay for treatment, which is often lengthy and very expensive."
Bayly said that an accurate prognosis can be very difficult with pleuropneumonia, and it is commonly misdiagnosed--it can be confused with mild colic, laminitis, or exertional rhabdomyolysis (tying-up). As recently as 10 years ago, this disease had a high mortality rate (50-75%). In horses that die, two-thirds had abscesses in their lungs. "With improved diagnostic abilities, more awareness of the disease, and improved treatment, mortality has decreased, but morbidity (illness rate) is still high," added Bayly.
The disease can "start" in a number of ways. Often it is associated with transport, stress, or severe exercise (such as racing). There might be a mild infection or pneumonia (frequently caused by a virus) involved early on. Following the stress come pulmonary changes and possibly secondary bacterial infections.
The progress of the disease breaks down into three categories as follows:
The peracute stage starts one to four days after the onset of illness. It's characterized by "friction rubs" between alveoli (air sacs in the lung) that can be heard with a stethoscope, but lung sounds can be heard in all lung fields. There is little or no lung fluid, but the horse has a fever. This stage can be mistaken for other things such as laminitis, colic, or tying-up. The horse has normal fibrinogen (a blood clotting factor that can convert to fibrin) and packed cell volume (PCV) blood tests. If diagnosed at this stage, the survival rate is 80%.
Pleurodynia means pleural pain (pain in the lining of the chest). In this stage, there is a characteristic shallow breathing pattern. The horse is reluctant to move, keeps his elbows abducted (spread apart), is intolerant of a rebreathing bag test (placing a bag over his nose), is painful to percussion (sharp tapping) and pressure on the thorax (between the neck and the abdomen), and has painful coughing.
If you can stand behind or above and behind a horse with this stage, it will be apparent that the horse is moving more air into one side of his lungs than the other. In most cases of pleuropneumonia, the right side is more affected, and the left side moves out more easily.
The acute stage lasts two to 14 days. Lung sounds are dull ventrally (on the lower portion of the lung), friction rubs can be heard more dorsally (top part of the lung), and your veterinarian will be able to percuss (tap with his fingers) a fluid line in the lungs. Sometimes there is pectoral (chest) edema, and the horse will have bad breath.
Fluid can be drained out of the lung in this stage, and is yellow or yellow/red--up to 2.6-5.2 gallons (10-20 liters) from one side of the chest. These animals are often dehydrated, have a fever, and are depressed, in pain, and in shock. Prognosis for survival is good if a Gram-positive organism (identified by a common laboratory test) is causing the pleuropneumonia. If a Gram-negative or anaerobic organism is the cause, then the chance of survival is reduced.
A horse is considered to be a chronic case when he has had the illness for at least two weeks. In these horses, fibrin (an insoluble protein) is beginning to organize, so there are multiple places in the lung with fluid trapped in pockets.
"That makes it hard to remove the fluid all at once," said Bayly.
Some horses have an intermittent low-grade fever, or a fever of unknown origin, and they lose weight as lung abscesses form. There often is little other outward sign. This "silent killer" type of pleuropneumonia has a survival prognosis of less than 50%. "These horses gradually waste away," said Bayly.
A definitive diagnosis is based on history, whether the horse had a recent upper respiratory tract infection (runny nose or maybe coughing), plus stress, exercise, transport, and/or anesthesia.
"Ultrasound has done more to promote early diagnosis and understanding of the pleural disease process than anything else in the last 20 years," said Bayly. "Ultrasound is almost essential to diagnosis, but it is essential to effectively monitor the progress of the animal during its course of treatment. You should scan the horse's chest on a daily basis."
Thoracocentesis (chest taps to get fluid for laboratory analysis) should be performed on both sides of the chest regardless of whether you think there is fluid, said Bayly. "This can be painful for the horse, but it can be performed in conjunction with ultrasound."
Blood work also is useful, with the level of fibrinogen a useful prognostic indicator of pleuropneumonia severity. "Greater than 10 grams per liter (g/l) means a poor
prognosis (4 g/l is normal)," noted Bayly. "Blood work is also helpful in monitoring response to treatment."
The successful management of pleuropneumonia depends on the duration of the disease (the longer the animal has it, the worse the outcome), how soon a diagnosis was made, how closely the horse is monitored, how intensively he is treated, and the causative organism(s).
The first goal of treatment is to "get that stuff out of there," said Bayly. Effective antimicrobial therapy is essential. Sometimes broad-spectrum antibiotics have to be introduced because your veterinarian can't wait to see what organisms are cultured in the laboratory.
"Even if you take as much fluid out as you can on day one, because it is a dynamic situation, some fluid will return to the chest," warned Bayly. "It is likely you will have to drain again. In difficult cases you can place an indwelling catheter or drain."
Good supportive care--nursing and nutrition--is important. Bronchodilators have been suggested by some clinicians, but Bayly said he didn't feel they had much benefit.
Hurdles for pleuropneumonia treatment include massive pulmonary abscessation, necrosis of tissues, proliferation of anaerobic and Gram-negative agents, and antibiotic inactivation or lack of penetration. Sometimes the antimicrobials can't get to the organisms if they are "walled off" in pockets in the lungs.
When is pleuropneumonia a medical vs. surgical problem? "There's no question that in the progress of some of these cases, no form of medical therapy is going to result in a successful outcome," said Bayly. "Some cases will only survive with surgical intervention."
"Surgery sometimes is necessary because unless diseased tissue is removed, treatment is pointless," said Bayly. "We do these animals standing because their ventilation ability already is compromised."
Bayly said the problem is deciding when to cut the horse's chest open. "That surgery means it will be a long time before the horse is right again. Tissue often has to be removed more than once, sometimes once every other day, so healing takes a long time. The horse will get very thin, and it's a long-term project. It can take six to 12 months to heal."
MESSAGE FROM THE WEVA PRESIDENT
Des Leadon, MA, MVB, MSc, FRCVS, RCVA, of the Irish Equine Center is the current president of the World Equine Veterinary Association (WEVA). He wants to lead the organization down a more defined path. Leadon said the board of directors wants WEVA to be "a funnel rather than an umbrella," existing for the purpose of sharing knowledge with veterinarians from around the world who might--without direct, focused help--find it harder to obtain up-to-date information on the care and management of equids.
He suggested that WEVA will seek to assist in the dissemination of knowledge of equine medicine and surgery by: 1) Adding to the international contributions at various countries' national equine conferences; and 2) Using funds from those joint meetings and donations to provide continuing education for practitioners in countries with emerging or less-developed equine veterinary continuing education programs.
Leadon wants to expand the current WEVA Executive Committee to include the secretaries of equine veterinary associations from around the world. This should improve
information dissemination. He also wants to do away with WEVA dues and instead take donations of money or support for speakers as a particular group's contribution to a WEVA meeting or session.
Leadon was scheduled to meet with the boards of the British Equine Veterinary Association and the American Association of Equine Practitioners to seek a working relationship with those large groups.
It was suggested that in addition to veterinary education assistance, board member Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, should explore the possibility of working with the veterinary groups in Turkey, India, and the Ukraine, with the guidance of Japanese board member Miki Tokuriki, a representative of one of the newly forming equine associations of the Asiatic countries over the next two or three years. -- Kimberly S. Graetz
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.
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