Critical Care In the Field
How does your veterinarian keep up with what is best for your horses? By attending continuing education that covers areas of interest and provides him with lectures and one-on-one time with experts in various fields. Each year, Hagyard Equine Medical Institute holds such a continuing education symposium in Lexington, Ky., and The Horse is taking you into the lecture room to let you know what your veterinarians are discussing.
The Equine Medical and Surgical Care for the Field Veterinarian seminar was held Oct. 19-22, 2005. A full day of wet labs devoted to emergency response techniques, lameness evaluation, and ultrasonographic examination of the adult abdomen, thorax, eye, and distal (lower) limb was followed by 2 1/2 days of lectures with 23 presentations by 19 speakers. Roughly half of the presenters were specialists at Hagyards; the others were experts from universities in the United States and Canada. Presenters covered topics ranging from managing chronic diseases to performing emergency treatments. More than 300 U.S. veterinarians and a handful of international guests attended, and 46 exhibitors participated in the associated trade fair.
"The symposium committee has a goal of providing an atmosphere of cordial interaction with our colleagues," said Fairfield T. Bain, DVM, Dipl. ACVIM, ACVP, ACVECC, MBA, of Hagyard. "The hope is that people can feel like they can have a conversation and learn in a smaller group atmosphere. We always want to present the latest new techniques as much as possible and to distill things to a practical level that can be used when an attendee returns to his or her home practice."
Following are highlights from the symposium.
Non-Infectious Respiratory Disease
Bonnie Rush, DVM, MS, Dipl. ACVIM, professor of equine medicine at Kansas State University, discussed managing recurrent airway obstruction (RAO, also called heaves, broken wind, emphysema, or COPD). "Reduce inflammation, relieve symptoms, and address allergen exposure; these are the most critical components of treatment," Rush said. "Recognize the trigger in the vast majority of these horses is molds in the environment. Nothing is worse for horses with heaves than round bale hay. Getting that round bale out of their lives will make a lot of difference."
She said she realizes that eliminating all dust to help the horse with hyper-reactive airways isn't possible, but she offered these suggestions:
- Don't store hay in the same area as the indoor arena or in lofts above the stalls;
- Soak the horse's hay before feeding; and
- Feed a complete pelleted diet.
In treating severe heaves, "It's important that you use systemic corticosteroids--aerosolized corticosteroids are not powerful enough," she explained. "Then use an aerosolized short-acting bronchodilator such as albuterol." The two drugs work synergistically to relax and open the airways.
She explained that inhalation is the ideal way to administer respiratory medication for horses with mild to moderate heaves, but it is important to recognize that only 8-9% of aerosolized drugs reach the lower airway with current delivery devices (Aeromask and Equine Haler). A previously available inhaler device (Torpex) delivered 43% of each actuation (puff) to the lung. She encouraged veterinarians to lobby for a re-release of the device, which was made by 3M for Boehringer-Ingelheim.
Infectious Respiratory Disease
Also discussed were preventive measures for three common respiratory infections.
Influenza--"Equine influenza is the most economically important contagious respiratory disease in horses," Rush said. Standard definitive diagnosis can take several days, so she suggested using a human influenza A kit that can return an accurate result in minutes. An intranasal modified-live influenza vaccine produces resistance against the virus within seven days and is effective for up to six months. "If you are looking at a disease outbreak, this is the most rapid vaccine we have," Rush said.
Equine herpesvirus--The severity of equine herpesvirus type-1 (EHV-1) and EHV-4 cases is determined by the viral strain, immune status, and age of the horse. Foals should be vaccinated for EHV at four months of age, and two inoculations should follow to complete the initial series. Boosters should be given every three to six months.
Strangles--Caused by Streptococcus equi, strangles has a low mortality rate (about 3%), but it is very contagious and spreads rapidly. Complications occur in up to 20% of cases. "The most frequent complication is metastatic spread of the infection to lymph nodes and organs in the head (bastard strangles)," Rush explained. "A live intranasal vaccine provides local mucosal immunity at the portal of entry," she said.
Farm Management of Rhodococcus equi
R. equi pneumonia in foals is expensive to treat, sometimes deadly, and R. equi-endemic farms (farms that have the bacteria constantly) often endure a stigma because of it. Nathan Slovis, DVM, Dipl. ACVIM, infectious disease chairman at Hagyard, said mares can shed R. equi in their manure, but a study he and colleagues completed found their foals aren't considered at a higher risk for R. equi.
"You have a greater impact on the burden of disease with control and prevention of R. equi pneumonia than treatment," Slovis said. He has directed a prevention program for four years on an endemic Kentucky farm involving administration of anti-R. equi hyperimmune plasma at birth and when the foal is 25 days old, analyzing tracheobronchial aspirates, and performing twice monthly thoracic ultrasounds to detect early signs. If he detects an ultrasonographic lesion, he starts the foal on a preventive course of antibiotics (choices include erythromycin, rifampin, and clarithromycin or Biaxin, which is now available in generic form, offering significant savings to the owner). It costs about $1,200 per foal to maintain the prophylactic program, which is a small fee considering that many of the foals are million-dollar racing prospects.
"To date, there have been no deaths on this farm due to R. equi," he said.
Slovis said scientists are exploring ways to promote mucosal immunity to R. equi through DNA vaccines.
Dexamethasone suppression tests (DST), the current gold standard for detecting equine pituitary pars intermedia dysfunction (PPID; also known as Cushing's disease), can produce unreliable results in up to 40% of clinically normal animals during the fall months because of the increased concentration of adrenocorticotrophic hormone (ACTH) during those months, said Dianne McFarlane, DVM, PhD, Dipl. ACVIM, ABVP, of Oklahoma State University.
For a DST, a veterinarian draws a small amount of blood before and after cortisone administration to determine the horse's response to excess cortisone. Excessive production of cortisol by the horse's adrenal glands may contribute to the signs of Cushing's, which include weight loss and laminitis. McFarlane said the test might also fail to identify horses with Cushing's disease if they have early or mild disease.
"Diagnosis of early PPID is problematic, and repetitive testing may be necessary," McFarlane said. "Seasons must be considered when interpreting diagnostic test results, and test results should always be interpreted in light of clinical findings."
Managing acute laminitis--James K. Belknap, DVM, PhD, of the Department of Veterinary Clinical Sciences at The Ohio State University, has aligned his laminitis research with human sepsis (bacteria in the blood circulation) research. "Laminar failure (when the laminae, or the tissue that holds the hoof wall to the coffin bone, fails) is very similar to organ failure in humans in terms of inflammation," he said.
Belknap believes a cocktail of bacterial toxins and cytokines (substances produced by white blood cells when there is inflammation in the body) triggers laminitis in most cases. "We recently found that in the prodromal/developmental stage of laminitis (no clinical signs of lameness, hoof warmth, bounding pulses, etc.), there is an intense inflammatory process occurring in the digital laminae as evidenced by an influx of leukocytes (white blood cells)," he said. There also are five- to 1,000-fold increases in inflammatory mediators such as cytokines and cyclooxygenase-2 (COX-2, a harmful enzyme). For this reason, Belknap aggressively treats animals at risk of laminitis and those in the acute stages of laminitis (which he considers the first two to four weeks of clinical signs) with non-steroidal anti-inflammatory drugs (NSAIDs) such as flunixin meglumine or Banamine, phenylbutazone, and ketoprofen. However, he cautioned that the use of COX-2 selective drugs in the early stages of the disease process might have the same negative vascular effects that have been found recently in humans (increased heart attacks and strokes due to vascular thrombosis or blood clot formation) in human patients taking COX-2 selective drugs), as he has now shown evidence of severe vascular inflammation in the early stages of the laminitic process.
Belknap emphasized that unless you apply cushion support material such as silicon putty to the solar surface of the feet, you should never leave conventional shoes on a horse at risk or in the acute stages of laminitis because it leaves P3 (the coffin bone) unsupported and puts all the stress on the hoof wall and laminae. "I think it's better to have the shoe off, take the pressure off the wall and laminae, and give at least some solar support of P3," he said. He suggests applying two-inch construction grade Styrofoam insulation to the feet as described by Gene Ovnicek, GPF, RMF (a farrier, clinician, and researcher who studies wild horse hoof form and function) and others, or making custom pads out of the commercially available silicon putties (supplied by both Nanric Inc. and EDSS Inc.) until the animals are ready for corrective shoeing.
Managing chronic laminitis--Hagyard's Robert Hunt, DVM, MS, Dipl. ACVS, said that laminitis is, "A vertical load of 1,200 pounds driving down on the bone column (down the leg to the coffin bone). We're trying to counteract all this force on this area that's four to five inches in diameter."
Hunt considers the duration, severity, and stability of each chronic laminitis case and makes sure he has the best radiographs possible when making a decision on management. "The most important part of treating a laminitic horse is talking to the owner," he said. "They (the horse owner) can do a beautiful job in managing the case, but you need to tell them the grim truth--you're going to lose the majority of these battles."
Chronically laminitic horses generally need special housing arrangements, and Hunt said providing soft flooring and footing is just as beneficial as corrective shoeing. He prefers stabling chronic cases on chopped rubber mulch with wood shavings. Goals should be to unload the laminae, ease breakover, and reduce tension. He prefers letting the horse go barefoot because it allows growth of a better hoof wall.
The Hagyard Bluegrass Equine Reproduction Symposium will be held Oct. 18-21, 2006 in Lexington, Ky. (see www.hagyard.com/symposium).
EQUINE VETERINARY TECHNICIAN SYMPOSIUM: Something for Techs
In addition to the Hagyard Bluegrass Equine Symposium, Hagyard Equine Medical Institute hosted the first American Association of Equine Veterinary Technicians (AAEVT) South Central Regional Symposium (Oct. 20-22, 2005). More than 75 technicians from across the country attended the meeting, which used some of the Bluegrass Symposiumspeakers and topics, but also included topics tailored specifically for technicians.
Following are a few of the topics covered at the AAEVT meeting.
Respiratory Distress and Stabilization Techniques--Hagyard's Michele L. Frazer, DVM, Dipl. ACVIM, explained the trans-tracheal wash procedure, which supplies a cleaner sample of tracheal fluid for testing than a tracheal wash, but has the potential for infection and accidental laceration of other structures. She discussed diagnosis and treatment of pleuropnemonia, instructing technicians on how to use a chest drain. She also reviewed how to perform tracheostomies in horses with blocked airways.
Equine Clinical Nutrition--Sick horses require specialized diets, which can vary depending on the horse's illness and body condition. Mary Beth Gordon, PhD, an equine nutritionist for Purina Feeds, offered advice on feeding horses affected by gastrointestinal disorders, laminitis, Cushing's, and other ailments.
She recommended optimizing hind gut fermentation in horses with small intestine disorders by feeding highly digestible fiber sources such as quality alfalfa hay. Feeding alfalfa hay four times a day (along with omeprazole treatment) can also reduce gastric ulcers.
Laminitic horses and horses with Cushing's should be fed a low-carbohydrate diet such as quality grass hay. Soaking the hay can decrease its carbohydrate content.
Infectious Disease Protocol for the Equine Hospital--"In order to prevent the dissemination of disease at your facility, you first must understand the pathology and disease course of the pathogen," said Nathan Slovis, DVM, Dipl. ACVIM, infectious disease chairman at Haygard Equine Medical Institute. "Second, you must educate your hospital staff about the disease and importance of hygiene."
Slovis discussed specific complications and protocols for diseases such as Clostridium, Salmonella, and rotavirus. He said clinics should devise protocols to routinely monitor for pathogens in horses and the environment. Slovis recommended several disinfectants to reduce the threat of pathogens, including Tek-Trol, Environ, and 1-Stroke. He also stressed using appropriate hand hygiene using antibacterial soap or gel.
Hagyard Equine Medical Institute and Rood and Riddle Equine Hospital, also in Lexington, Ky., are teaming up to host the next South Central Regional Symposium on Aug. 24-26, 2006.--Stephanie L. Church and Chad Mendell
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POLL: University Equine Hospitals