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The Modern

Equine Vet www.modernequinevet.com

Vol 5 Issue 7 2015

Mystery Wound Injecting the navicular bursa Ultrasonography & palpation for colic


Table of Contents

Cover story:

12 Big thoroughbred

with big infection Cover: courtesy of New Bolton Equine Hospital

Orthopedics

Is there a better way to inject the navicular bursa?.....................................................4 Gastrointerology

Ultrasonography and palpation for colic..........................................................................6 Nutrition

Bioactive proteins and their role in health...................................................................14 Infectious diseases

EIV increases in older horses..............................................................................................16 News

Happy anniversary, Ruffian..........................................................8 Pony up an immune response.....................................................9 Reduced oxytocin and retained fetal membrane.........10 Diffusion of mepivicaine from tendon sheaths.............15 advertisers MERCK Animal Health................................................. 3 Luitpold Animal Health.............................................. 7

Lifeline Proformance Supplements.......................11

The Modern

Equine Vet Sales: Robin Geller • newbucks99@yahoo.com Editor: Marie Rosenthal • mrosenthal@percybo.com Art Director: Jennifer Barlow • jbarlow@percybo.com contributing writerS: Paul Basillo • Kathleen Ogle Louisa Shepard • Carrie Hammer DVM, PhD COPY EDITOR: Patty Wall Published by PO Box 935 • Morrisville, PA 19067 Marie Rosenthal and Jennifer Barlow, Publishers percybo media  publishing

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Issue 7/2015 | ModernEquineVet.com

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© 2015 Intervet Inc., d/b/a Merck Animal Health, a subsidiary of Merck & Co., Inc. All rights reserved. Photography: Vince Cook. 50034 7/13 EQ-BIO-1217-AD


orthopedic

Regu-Mate® (altrenogest) Solution 0.22% (2.2 mg/mL) CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian. DESCRIPTION: Regu-Mate® (altrenogest) Solution 0.22% contains the active synthetic progestin, altrenogest. The chemical name is 17α-allyl-17ß-hydroxyestra-4,9,11-trien-3-one. The CAS Registry Number is 850-52-2. The chemical structure is: Each mL of Regu-Mate® (altrenogest) Solution 0.22% contains 2.2 mg of altrenogest in an oil solution. ACTIONS: Regu-Mate® (altrenogest) Solution 0.22% produces a progestational effect in mares.

Is there a better way to inject

INDICATIONS: Regu-Mate® (altrenogest) Solution 0.22% is indicated to suppress estrus in mares. Suppression of estrus allows for a predictable occurrence of estrus following drug withdrawal. This facilitates the attainment of regular cyclicity during the transition from winter anestrus to the physiological breeding season. Suppression of estrus will also facilitate management of prolonged estrus conditions. Suppression of estrus may be used to facilitate scheduled breeding during the physiological breeding season.

navicular

CONTRAINDICATIONS: Regu-Mate® (altrenogest) Solution 0.22% is contraindicated for use in mares having a previous or current history of uterine inflammation (i.e., acute, subacute, or chronic endometritis). Natural or synthetic gestagen therapy may exacerbate existing low-grade or “smoldering” uterine inflammation into a fulminating uterine infection in some instances. PRECAUTIONS: Various synthetic progestins, including altrenogest, when administered to rats during the embryogenic stage of pregnancy at doses manyfold greater than the recommended equine dose caused fetal anomalies, specifically masculinization of the female genitalia. DOSAGE AND ADMINISTRATION: While wearing protective gloves, remove shipping cap and seal; replace with enclosed plastic dispensing cap. Remove cover from bottle dispensing tip and connect luer lock syringe (without needle). Draw out appropriate volume of Regu-Mate solution. (Note: Do not remove syringe while bottle is inverted as spillage may result.) Detach syringe and administer solution orally at the rate of 1 mL per 110 pounds body weight (0.044 mg/kg) once daily for 15 consecutive days. Administer solution directly on the base of the mare’s tongue or on the mare’s usual grain ration. Replace cover on bottle dispensing tip to prevent leakage. Excessive use of a syringe may cause the syringe to stick; therefore, replace syringe as necessary. WHICH MARES WILL RESPOND TO REGU-MATE® (altrenogest) SOLUTION 0.22%: Extensive clinical trials have demonstrated that estrus will be suppressed in approximately 95% of the mares within three days; however, the post-treatment response depended on the level of ovarian activity when treatment was initiated. Estrus in mares exhibiting regular estrus cycles during the breeding season will be suppressed during treatment; these mares return to estrus four to five days following treatment and continue to cycle normally. Mares in winter anestrus with small follicles continued in anestrus and failed to exhibit normal estrus following withdrawal. Response in mares in the transition phase between winter anestrus and the summer breeding season depended on the degree of follicular activity. Mares with inactive ovaries and small follicles failed to respond with normal cycles post-treatment, whereas a higher proportion of mares with ovarian follicles 20 mm or greater in diameter exhibited normal estrus cycles posttreatment. Regu-Mate® (altrenogest) Solution 0.22% was very effective for suppressing the prolonged estrus behavior frequently observed in mares during the transition period (February, March and April). In addition, a high proportion of these mares responded with regular estrus cycles post-treatment. SPECIFIC USES FOR REGU-MATE® (altrenogest) SOLUTION 0.22%: SUPPRESSION OF ESTRUS TO: 1. Facilitate attainment of regular cycles during the transition period from winter anestrus to the physiological breeding season. To facilitate attainment of regular cycles during the transition phase, mares should be examined to determine the degree of ovarian activity. Estrus in mares with inactive ovaries (no follicles greater than 20 mm in diameter) will be suppressed but these mares may not begin regular cycles following treatment. However, mares with active ovaries (follicles greater than 20 mm in diameter) frequently respond with regular post-treatment estrus cycles. 2. Facilitate management of the mare exhibiting prolonged DOSAGE CHART: estrus during the transition period. Estrus will be suppressed in mares exhibiting prolonged behavioral estrus either early Approximate Weight Dose or late during the transition period. Again, the posttreatment in Pounds in mL response depends on the level of ovarian activity. The 770 7 mares with greater ovarian activity initiate regular cycles 880 8 and conceive sooner than the inactive mares. Regu-Mate® 990 9 (altrenogest) Solution 0.22% may be administered early in 1100 10 the transition period to suppress estrus in mares with inactive 1210 11 ovaries to aid in the management of these mares or to mares 1320 12 later in the transition period with active ovaries to prepare and schedule the mare for breeding. 3. Permit scheduled breeding of mares during the physiological breeding season. To permit scheduled breeding, mares which are regularly cycling or which have active ovarian function should be given Regu-Mate® (altrenogest) Solution 0.22% daily for 15 consecutive days beginning 20 days before the date of the planned estrus. Ovulation will occur 5 to 7 days following the onset of estrus as expected for nontreated mares. Breeding should follow usual procedures for mares in estrus. Mares may be regulated and scheduled either individually or in groups. ADDITIONAL INFORMATION: A 3-year well controlled reproductive safety study was conducted in 27 pregnant mares, and compared with 24 untreated control mares. Treated mares received 2 mL Regu-Mate® (altrenogest) Solution 0.22% /110 lb body weight (2x dosage recommended for estrus suppression) from day 20 to day 325 of gestation. This study provided the following data: 1. In filly offspring (all ages) of treated mares, clitoral size was increased. 2. Filly offspring from treated mares had shorter interval from Feb. 1 to first ovulation than fillies from their untreated mare counterparts. 3. There were no significant differences in reproductive performance between treated and untreated animals (mares & their respective offspring) measuring the following parameters: • •

• • • • • • •

interval from Feb. 1 to first ovulation, in mares only. mean interovulatory interval from first to second cycle and second to third cycle, mares only. follicle size, mares only. at 50 days gestation, pregnancy rate in treated mares was 81.8% (9/11) and untreated mares was 100% (4/4). after 3 cycles, 11/12 treated mares were pregnant (91.7%) and 4/4 untreated mares were pregnant (100%). colt offspring of treated and control mares reached puberty at approximately the same age (82 & 84 weeks respectively). stallion offspring from treated and control mares showed no differences in seminal volume, spermatozoal concentration, spermatozoal motility, and total sperm per ejaculate. stallion offspring from treated and control mares showed no difference in sexual behavior. testicular characteristics (scrotal width, testis weight, parenchymal weight, epididymal weight and height, testicular height, width & length) were the same between stallion offspring of treated and control mares.

REFERENCES: Shoemaker, C.F., E.L. Squires, and R.K. Shideler. 1989.Safety of Altrenogest in Pregnant Mares and on Health and Development of Offspring. Eq. Vet. Sci. (9); No. 2: 69-72. Squires, E.L., R.K. Shideler, and A.O. McKinnon. 1989.Reproductive Performance of Offspring from Mares Administered Altrenogest During Gestation. Eq. Vet. Sci. (9); No. 2: 73-76. WARNING: Do not use in horses intended for food. HUMAN WARNINGS: Skin contact must be avoided as Regu-Mate® (altrenogest) Solution 0.22% is readily absorbed through unbroken skin. Protective gloves must be worn by all persons handling this product. Pregnant women or women who suspect they are pregnant should not handle Regu-Mate® (altrenogest) Solution 0.22%. Women of child bearing age should exercise extreme caution when handling this product. Accidental absorption could lead to a disruption of the menstrual cycle or prolongation of pregnancy. Direct contact with the skin should therefore be avoided. Accidental spillage on the skin should be washed off immediately with soap and water. INFORMATION FOR HANDLERS: WARNING: Regu-Mate® (altrenogest) Solution 0.22% is readily absorbed by the skin. Skin contact must be avoided; protective gloves must be worn when handling this product. Effects of Overexposure: There has been no human use of this specific product. The information contained in this section is extrapolated from data available on other products of the same pharmacological class that have been used in humans. Effects anticipated are due to the progestational activity of altrenogest. Acute effects after a single exposure are possible; however, continued daily exposure has the potential for more untoward effects such as disruption of the menstrual cycle, uterine or abdominal cramping, increased or decreased uterine bleeding, prolongation of pregnancy and headaches. The oil base may also cause complications if swallowed. In addition, the list of people who should not handle this product (see below) is based upon the known effects of progestins used in humans on a chronic basis. PEOPLE WHO SHOULD NOT HANDLE THIS PRODUCT. 1. 2. 3. 4. 5. 6. 7. 8.

Women who are or suspect they are pregnant. Anyone with thrombophlebitis or thromboembolic disorders or with a history of these events. Anyone with cerebral-vascular or coronary artery disease. Women with known or suspected carcinoma of the breast. People with known or suspected estrogen-dependent neoplasia. Women with undiagnosed vaginal bleeding. People with benign or malignant tumors which developed during the use of oral contraceptives or other estrogen-containing products. Anyone with liver dysfunction or disease.

ACCIDENTAL EXPOSURE: Altrenogest is readily absorbed from contact with the skin. In addition, this oil based product can penetrate porous gloves. Altrenogest should not penetrate intact rubber or impervious gloves; however, if there is leakage (i.e., pinhole, spillage, etc.), the contaminated area covered by such occlusive materials may have increased absorption. The following measures are recommended in case of accidental exposure. Skin Exposure: Wash immediately with soap and water. Eye Exposure: Immediately flush with plenty of water for 15 minutes. Get medical attention. If Swallowed: Do not induce vomiting. Regu-Mate® (altrenogest) Solution 0.22% contains an oil. Call a physician. Vomiting should be supervised by a physician because of possible pulmonary damage via aspiration of the oil base. If possible, bring the container and labeling to the physician. CAUTION: For oral use in horses only. Keep this and all medication out of the reach of children. Store at or below 25°C (77°F). NADA# 131-310, Approved by FDA. HOW SUPPLIED: Regu-Mate® (altrenogest) Solution 0.22% (2.2 mg/mL). Each mL contains 2.2 mg altrenogest in an oil solution. Available in 1000 mL plastic bottles. * US Patents 3,453,267; 3,478,067; 3,484,462 Manufactured by: DPT Laboratories, San Antonio, TX 78215 Distributed by: Intervet Inc., Millsboro, DE 19966

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Although injection of the navicular bursa often is performed from the palmar aspect of the limb, a better option might be approaching from the lateral aspect so that one can avoid penetrating the deep digital flexor tendon (DDFT), according to a recent study. “Some clinicians are concerned regarding DDFT puncture and worry about possible cumulative damage,” explained Alexander Daniel, BVetMed, MS, DACVS, an equine surgeon at Reid and Associates Equine Clinic in Loxahatchee, Fla. “The only way to avoid this is to approach the bursa from the lateral aspect.” Injection from the palmer aspect penetrates the DDFT, requires the limb to remain flexed during the injection and does not often result in the retrieval of enough synovial fluid for testing if infection is suspected, the researchers said. They wanted to find a better technique for the radiographic guided injection of the navicular bursa that could avoid these issues. In a prospective clinical and cadaver study, Dr. Daniel and his colleagues evaluated a lateral injection technique.

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“Our main goal was to ensure that the DDFT would not be punctured since this tendon is always punctured using the traditional palmar approach. We also wanted to see what structures might be punctured from the lateral approach. We did this by comparing radiographs and MRI with the needle in place to allow us to correlate what we do in a clinical setting [inject under radiographic guidance] with MRI,” he said. (Only the cadaver limbs were examined using MRI.) The researchers placed 40 cadaver equine limbs in a stand to stimulate weight bearing and then injected them using a lateral injection technique. They also laterally injected 31 living horses that presented with palmer foot pain. The researchers were successful in injecting all 71 limbs. They found that the relative risk of puncturing the distal interphalangeal (DIP) joint was 19 times higher (95% CI 1.3–285.4, P<0.001) when the distal interphalangeal (DIP) joint was distended than in a more normal position. The relative risk of puncturing the DFTS was 2.7 times higher (95% CI 1.0–7.2, P=0.06) when the DFTS was distended than in normal limbs. They were able to aspirate synovial fluid from the navicular bursa in 47% of clinical cases. Three of those

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appeared to be septic. “There are typically two situations we need to place a needle into the navicular bursa, either we are concerned regarding a septic process and need to sample the bursal fluid or we need to administer a therapeutic to treat a lameness issue,”he said. “We found that the position of the needle helps us obtain fluid more consistently from the lateral approach than the palmar approach. This is crucial as part of the decision process, especially if surgery might be involved, e.g. due to infection. If we are using a therapeutic such as IRAP [Interleukin-1 Receptor Antagonist Protein], there are some horses that need a series of injections and the lateral approach allows us to do this without placing a needle through the tendon on multiple occasions.” The researchers wrote that even though there was no clear evidence to show that penetrating the DDFT joint repeatedly causes harm, they felt that the lateral approach, which avoids this, was a better option because it does not affect any tendon, ligamentous or cartilage. There is a risk of synovial penetration which could spread organisms if there is a deep digital flexor sheath or DIP joint infection, so synovial fluid should be analyzed first to avoid inMeV fecting the bursa, he added.

For more information: Daniel AJ, Goodrich LR, Barrett MF, et al. An optimized injection technique for the navicular bursa that avoids the deep digital flexor tendon. Equine Vet J. 2014 Dec 23. doi: 10.1111/evj.12402. [Epub ahead of print]. http://onlinelibrary.wiley.com/doi/10.1111/evj.12402/abstract;jsessionid=37E641457FF2F5278C1A2A95D273858E.f03t03

©shutterstock/Marcel Jancovic

bursa?

Some clinicians worry about hitting the deep digital flexor tendon and possible cumulative damage.

ModernEquineVet.com | Issue 7/2015

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Gastroenterology

Ultrasonography and Palpation:

Photo courtesy of Brad McHugh, Director, Veterinary FujiFilm SonoSite

Perfect Together

B y In the examination of a

horse with abdominal pain related to colic, the combined overall picture provided by transabdominal ultrasonography and palpation per rectum (PPR) is greater than the sum of its parts. “If we combine these findings, we are able to gain much more information about the ‘black box’ inside our patient than we would be able

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P a u l

B a s i l i o

to from either one alone,” explained Tracy Norman, DVM, DACVIM, associate veterinarian at the Blue Ridge Veterinary Clinic in Virginia.

Limitations

While both modalities are important for the overall picture, there are limitations to each. Rectal examination may not be possible in certain patients due to

age, infirmity, or size. In a very large horse, palpation past the pelvic rim may be challenging. The space eaten up by gas distention and pregnancy may also get in the way of worthwhile findings. Even in ideal conditions, palpation via rectum is only useful to ascertaining the situation in the caudal third of the abdomen. For ultrasonography, gas dis-


tention can be a limitation as well. “If a horse has a gas-filled colon pressed up against the body wall, the only thing we’re going to see is the gas-filled colon,” Dr. Norman explained here at the 60th Annual AAEP Convention. Patient characteristics, such as thick skin, coarse hair, dirt in the haircoat, and excess adipose tissue can also hamper ultrasonographic examination. The other limitation is environmental. While some clinicians have the benefit of working in a climatecontrolled hospital environment, the vagaries of weather can hamper examinations in the field. When a cold horse vasoconstricts, the sound waves are going to have a much more difficult time penetrating to the area of interest. A blanket can be used to warm bodies in colder temperatures, but

most horses with painful abdomens will have spent most of the day wallowing in cold mud.

Time is money

Recent studies have investigated the utility of brief, limited, targeted ultrasonographic exams, and Dr. Normal reported the news is promising. “With a little training and practice, most of us can become pretty good at performing quick examinations to identify important information without a prohibitively expensive bill for the client.” The Fast Localized Abdominal Sonography (FLASH) exam is the most common of these limited examinations. It uses 7 discrete windows on either side of the horse’s abdomen and cranioventral thorax to obtain specific information about the horse, such as:

Tools of the Trade “Palpation per rectum does not take much in the way of equipment,” Dr. Norman said. “You’re going to need a lot of lube, and you’ll probably want a rectal sleeve of some type. Proper restraint is important for the patient’s safety and for ours. I’m not a tall person, so my footstool is standard equipment.” For diagnostic ultrasonography, it is easy to understand why it was initially dismissed as a useful diagnostic modality for acute abdomen. The machines were large, they were very expensive, and the images were difficult to interpret. Often, referral services were the only places that could afford the type of probes that had a frequency low enough to meaningfully penetrate in the horse’s abdomen. “However, technology is certainly coming along at a wonderful pace,” she explained. “There are commercial handheld units that are about the size of an iPod. Resolutions have improved, and the prices have come down. Units with battery packs are also available, which allows us to operate in areas where we don’t have a hard power source.”

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Now Available! There are no known contraindications to the use of intramuscular Adequan® i.m. brand Polysulfated Glycosaminoglycan in horses. Studies have not been conducted to establish safety in breeding horses. WARNING: Do not use in horses intended for human consumption. Not for use in humans. Keep this and all medications out of the reach of children. Caution: Federal law restricts this drug to use by or on the order of a licensed veterinarian. Each 5 mL contains 500 mg Polysulfated Glycosaminoglycan. Brief Summary Indications: For the intramuscular treatment of non-infectious degenerative and/or traumatic joint dysfunction and associated lameness of the carpal and hock joints in horses. See Product Package Insert at www.adequan.com for Full Prescribing Information Adequan® is a registered trademark of Luitpold Pharmaceuticals, Inc. © Luitpold Animal Health, division of Luitpold Pharmaceuticals, Inc. 2015. Photo by Anne M. Eberhardt, Copyright Blood-Horse Publications used with permission. Triple Crown is a registered trademark of Triple Crown Productions LLC. AHD132 Rev. 6/2015


Gastroenterology

• Is bowel present in the nephrosplenic space? • How much peritoneal fluid is present, and what does it look like? • Is there small intestine visible, and what does it look like? • Is the diaphragm intact? • Is the stomach distended? With those questions in mind, the clinician can place the ultrasound probe in the corresponding areas, collect the pertinent information, and move on. “Even a relatively inexperienced sonographer can finish that exam in about 10 minutes,” Dr. Norman said. “We have to stick around to see what the horse is going to look like after the xylazine wears off, so you might as well scan the horse while you’re waiting.”

Large colon and cecum

Common things happen commonly, and so the large colon and the cecum are often the focus when evaluating horses with abdominal pain. “These sites are often implicated in patients with abdominal pain because they can do a lot of things,” Dr. Norman said. “They can get stopped up, they can spasm, they can wander around to aberrant places, they can twist and telescope into themselves, and they can get infected.” PPR is an important part of the evaluation for impaction colic in-

The large colon and the cecum are often the focus when evaluating horses with abdominal pain. volving the pelvic flexure and the cecum. Ultrasonography tends to be less revelatory in cases where the impaction has not been in place long enough for vascular compromise of the colon. It can be difficult to look at a normal colon and be able to tell where the colon wall ends and the intestinal contents begin. For large colon displacement, the two modalities can work in concert. “On rectal examination in a horse with left displacement, we can feel the left colon coursing up through the nephrosplenic space,” Dr. Normal explained. “It’s difficult to say whether the colon is just ‘up there’ or if it’s entrapped in the space between the spleen and the kidney. On ultrasound, we get a better picture of this.” In these cases, the classical image involves the spleen. Deep and

dorsal to the spleen, a large loop of gas-filled bowel can be visualized. The image of the kidney is obscured by the gas. In contrast, it is possible for the colon to be on top of the spleen, but not entrapped in the nephrosplenic ligament. In a patient with large colon displacement on the right, ultrasonography can be helpful as well. On rectal palpation, a taut band can be felt coursing horizontally across the abdomen where it does not belong. If the bowel is empty, this finding may be missed. “If the bowel is full, it may be up where we can detect it,” Dr. Norman said. “If it is sunk down to the bottom of the abdomen, we may miss that on palpation. Finding edema of the large colon is highly suggestive of vascular compromise. You do not want to stick your arm into a horse with a large colon volvulus and restricted blood flow. Those horses get taken straight to surgery, because time is trauma.” Palpation of the horse’s rectum will generally yield results from the caudal third of the abdomen. Transcutaneous ultrasonography of the abdomen is useful for visualizing the outer third or sometimes half of the abdomen, including some solid organs. If the information from both of these modalities is combined, clinicians are afforded a much more complete picture than either one by itself. MeV

Happy anniversary, Ruffian ELMONT, NY – Cornell Ruffian Equine Specialists celebrated their first anniversary on June 25 with an event held at the practice, located right across the street from Belmont Park. Guests included Long Island-area owners, trainers, veterinarians, and other horse lovers. Dean Michael Kotlikoff announced that the client entrance at Ruffian would be named the Dan and Jane Burke Foyer, in recognition of the couple’s support of the equine program. It’s a longstanding relationship that began when Dan Burke brought his first horse to Cornell in the early 1950s. Ruffian opened on May 7, 2014 with Dr. Nixon, and Drs. Lisa Fortier and Norm Ducharme as the original medical team. The practice focuses on equine athletes, from Thoroughbred and Standardbred racehorses to sport horses that compete in dressage and jumping. Primary care veterinarians refer their patients 8

Issue 7/2015 | ModernEquineVet.com

for advanced diagnostic and medical care. Ruffian initially offered leading-edge orthopedic, respiratory, imaging and regenerative medicine services. Dr. Kyla Ortved and Dr. Samuel Hurcombe joined Ruffian in August, adding general surgery and emergency and critical care to the list. In their first year, Ruffian specialists and staff served about 1,000 horses, performing hundreds of procedures including bone scans, respiratory surgeries and fracture repair. The sophisticated imaging services at Ruffian expanded in June to include standing magnetic resonance imaging (MRI). Looking ahead, Dr. Nixon said the facility was planning to obtain a robotic CT scanner that can produce images of a horse’s entire body and an aquatread MeV rehabilitation system for rehabilitation.


news notes

Pony up an immune response or not pens in people with allergies. Understanding what triggers allergic reactions could help researchers come up with ways to stop people developing sensitivities. “We believe this finding could have direct practical implications, for example, by helping immune responses to choose the right direction in individuals who we would like to protect from developing occupation-associated allergies,” Dr. Zaiss said.

Photo courtesy of the University of Edinburgh.

The immune system of the Shetland pony can respond to midge bites in a way that prevents—rather than triggers—allergic reactions, researchers said. “To our knowledge, this is the very first study of a natural allergic disease in which we can show that immune responses to allergens can take two directions, either leading to allergy or to tolerance,” said Dr. Dietmar Zaiss, of the University of Edinburgh’s School of Biological Sciences, who led the study. It was previously thought that ponies that do not suffer an allergic reaction to bites do so because their immune system does not recognize allergens carried by the insects, and as a result do not respond. However, the Scottish researchers showed that all horses respond, and that their immune system can act in two different ways in response to the irritants in midge bites. One of these responses produces allergy symptoms, such as itching and inflammation, while the other prevents an allergic reaction, researchers said. The team found that after being exposed to midges, the equine immune system releases various cytokines that affect the behavior of other cells. Ponies that react to midge bites release cytokines—interleukin 4 (IL4)—that trigger allergy symptoms. In ponies not sensitive to bites, another cytokine—interferon-gamma (INF-g)—is released, which blocks different immune cells that would otherwise trigger allergic reactions. Allergies are caused by a complex interaction between genetic and environmental factors. Researchers said the reason why some individuals develop sensitivities to certain substances, while others do not, is not fully understood. It is unclear what causes the immune system to activate a protective response over an allergic one, the team said. Shetland ponies’ immune response to insect bites is helping scientists understand how people could be prevented from developing allergies. The ponies’ immune response to midge bites is similar to what hap-

“To our knowledge, this is the very first study of a natural allergic disease in which we can show that immune responses to allergens can take two directions, either leading to allergy or to tolerance.” Dr. Dietmar Zaiss, University of Edinburgh’s School of Biological Sciences,

The study, published in the journal PLOS One, was funded by the Dutch Foundation for Technical Sciences (STW) and was carried out in collaboration MeV with researchers in the Netherlands.

For more information: CMeulenbroeks C, van der Lugt JJ, van der Meide NMA, et al. Allergen-specific cytokine polarization protectsshetland ponies against Culicoides obsoletus-induced insect bite hypersensitivity. PLOS ONE, 2015;10:e0122090 DOI: 10.1371/journal.pone.0122090 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122090

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9


Theriogenology

Shutterstock/ CCimage

Reduced oxytocin expression with retained fetal membranes Reduced oxytocin expression in the uterus may be a contributing factor to the high incidence of secondary uterine atony and retained fetal membrane in heavy draught mares. This may be related to increasing age, according to Polish researchers Researchers from the University of Warmia and Mazury, in Olsztyn, Poland, investigated the expression of oxytocin receptors in heavy draught mares affected by retained fetal membranes. The researchers thought that one reason for the high incidence (50%) of retained fetal membranes in heavy draught mares may be a difference in the expression of uterine oxyctocin receptors. The researchers obtained placental biopsies from eight mares, four of which had passed fetal membranes normally within three hours of parturition (control mares) and four that retained fetal membranes due to secondary atony of the uterus. The mares with secondary atony of the uterus and retained fetal membranes were significantly older than control mares (average age in each group was 13 and 5 years respectively). C h e m i lu m i n e s c e nt western blotting was used to estimate the amount of oxytocin receptors in placental tissues (endometrium and allantochorion). In placental tissue from mares with retained fetal membranes, oxytocin expression was found to be 50 times less intense than in the placental tissue from control mares. Immunocytochemistry was used to determine the location of oxytocin receptors in the placental tissue. In cases of retained fetal membranes, the staining for oxytocin receptor expression was hardly visible. In control cases the staining was more intense, defining the locations where receptors were expressed. Expression of oxytocin receptors was particularly evident in the region where

the endometrium and allantochorion meet. As oxytocin expression is thought to be similar in both the endometrium and myometrium around the time of parturition, the researchers suggest that oxytocin expression in the myometrium may also be reduced, contributing to secondary uterine atony observed in cases of retained fetal membranes. It was postulated that age-related changes to receptor numbers and binding affinity may be related to this reducMeV tion by as yet undetermined mechanisms.

When membranes were retained, oxytocin expression was 50 times lower.

For more information: Rapacs-Leonard A., Ras A, Catka J, et al. Expression of oxytocin receptors is greatly reduced in the placenta of heavy mares with retained fetal membranes due to secondary uterine atony. Equine Vet J. 27 APR 2015 (Epub ahead of print) DOI: 10.1111/evj.12426. http://onlinelibrary.wiley.com/doi/10.1111/evj.12426/full 10

Issue 7/2015 | ModernEquineVet.com


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wound care

Medical Mystery:

Although Tractor was not

meant for the racetrack—secondto-last in his best race—he was clearly born to fly over open hills and jumps and was runner-up in the

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Issue 7/2015 | ModernEquineVet.com

2015 Pennsylvania Most-Wanted Thoroughbred competition at the World Horse Expo in Harrisburg. Sponsored by the Retired Racehorse Project, only four horses are

L o u i s a

chosen out of dozens of entries, based in part on a persuasive essay. But Tractor almost didn’t compete. Not long after Monica Fiss started training Tractor, a swol-

S h e p a r d

Photo courtesy of New Bolton Center.

Big Thoroughbred with big infection


len spot appeared under his belly. It didn’t seem to bother him, but it did her. An experienced horsewoman, she had never seen anything like it. “You could push your finger in it, and it was like pushing into a sandbag. The impression would stay,” said Fiss, who owns and operates a training, lesson and boarding barn, Windswept Stables, in Aberdeen, Md. The local veterinarian prescribed a topical medicine, and said to keep an eye on it. One day, Ms. Fiss saw a little scab. “It

surgery, discovered that the abscess was actually in the abdominal wall. The sack was enormous: 10 inches long and two inches wide. “We defined the margins, and it was too big to open the whole thing up, because of the risk of body wall herniation,” Dr. Parente said. “It was too big to take the whole thing out, too, because there wasn’t enough margin to put it back together.” The goal was twofold: to try to find out what caused the abscess, and to effectively drain it, Dr. Parente said. With ultrasound guidance, he inserted laparoscopic can-

going cross country. “Then, one day, I looked down, and the abscess was back,” she said. “It was leaking. I called Dr. Parente in tears. I thought we were going to have to put him down.” “I get a little emotional with this horse,” she continued. “I thought he was a goner. It was so sad for me.” But Dr. Parente told her to not give up. “I think what happened is that the infection hadn’t been

Since the wound was too large to open because of the risk of body wall herniation, the goal was to find out what caused the abscess and to effectively drain it. came off, and this really gross liquid came out, like a quart of it,” she said. “The smell was horrendous. It was mostly yellowy, white, cloudy pus. The poor guy.” The vet prescribed antibiotics, and a regimen of flushing with an antiseptic and salt water. But the abscess “wasn’t going away,” she said. So off they went to Manor Equine Hospital for an ultrasound, which showed a large abscess in the abdomen. “It was surgery, or death,” Fiss said. She brought him to New Bolton Center in Kenneth Square, Pa. Through a more advanced ultrasonography technique, Eric J. Parente, AB, DVM, professor of

nulas into the abscess sac through two small incisions, and flushed it out. He then inserted a special drain to administer a high concentration of local antibiotics over the next week. Tractor was put on systemic antibiotics as well. Once home, Ms. Fiss continued the care, administering a strong antibiotic three times a day for two weeks, as well as cleaning the wound site. Tractor was in quarantine because of the drug’s hazard to humans. Fiss wore safety goggles and gloves and a medical gown. She started riding him again about three months later, starting slow with walk-trot, then bringing up to a canter, jumping, and

completely resolved, so we put Tractor back on antibiotics,” he said, which resolved the infection. Although Dr. Parente solved the problem, he did not pinpoint the cause. “It is very unusual to have an abscess without a reason, puncture, or previous surgery,” Dr. Parente said. “There has to be some physiological reason. You have to presume there was a wound there at some point.” Ms. Fiss said neither she nor the breeder noted any wound. So for MeV now, it remains a mystery.

Tracktor competing after treatment.

Photo courtesy of New Bolton Center.

ModernEquineVet.com | Issue 7/2015

13


nutrition

Bioactive proteins

and their role in horse health C a r r i e

Optimal horse health and

well-being are the goals of every veterinarian and owner whether the horse is a high performance athlete or a beloved companion. Providing good nutrition is the foundation for achieving this goal; however, there are times that supplements or other treatment options are needed to balance what the horse requires. Making decisions on which supplement or treatment to recommend can be daunting for even the most knowledgeable owners, as there are hundreds of oral supplements on the market advertised to support a variety of conditions.

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Issue 7/2015 | ModernEquineVet.com

H a m m e r

D V M ,

Your advice is very important. One new supplement released last year is marketed as an orally dosed serum protein product. Although administering oral serum to neonatal foals with failure of passive transfer or with the use of injected autologous conditioned serum (ACS or IRAP) may be familiar, the thought of orally dosing serum proteins to horses may seem foreign. Traditionally, feeding of protein is talked about from a nutrition sense; i.e. the proteins incorporated in grasses and grains are ingested by the horse and broken down into

P h D

amino acids in the stomach and small intestine. These amino acids are then absorbed and re-assembled back into proteins that the body uses for various needs. However, in recent years, science has shown that after ingestion, some proteins can act within the body in ways that are different from the traditional nutrition pathway. These proteins have been named bioactive proteins and are defined differently among various scientific disciplines. Animal nutritionists define bioactive proteins as proteins that, when administered to the animal, improve animal performance and well-being beyond what can be explained solely by the understanding of basic nutrient digestion and absorption. For animals, the main sources of bioactive proteins are products purified from dried serum or milk. Milk-based oral products for horses have been commercially available for approximately 10 years, while the first serum-based oral product was introduced in 2014. Although relatively new to the horse industry, the beneficial effects of serumbased bioactive proteins are well documented in humans and food animals and products have been available for over 30 years. Serum is the fluid portion of blood remaining after the blood cells clot

Šshutterstock/Margo Harrison

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news notes

and is rich in bioactive proteins, including immunoglobulins, transferrins, cytokines and growth factors. Immunoglobulins are antibodies produced by the immune system and are responsible for protecting the body from infectious agents and toxins. Immunoglobulins act through a variety of complex mechanisms, ultimately rendering a disease unable to function. Transferrins are proteins that bind iron, an element necessary for the growth and development of many bacteria. Thus, transferrins create a low-iron environment that affects bacterial survival. Finally, there are numerous cytokines and growth factors present in serum, including interleukin-1, platelet-derived growth factor, transforming growth factor and insulin-like growth factor. Cytokines and growth factors function in cell signaling, tissue growth and many various cellular activities. One proposed mechanismof-action of bioactive proteins is through modulation of the immune system, which is the bodyâ&#x20AC;&#x2122;s defense against disease-causing pathogensâ&#x20AC;&#x201D;bacteria, viruses and toxins. Bioactive proteins reduce the ability of pathogens to attach and reproduce in the body, and also aid in tissue repair. These activities lead to beneficial support and maintenance of the immune system. Overall, the beneficial effects of bioactive proteins are more pronounced in higher stress situations, as these situations are known to in-

crease the release of inflammatory cells. Animals can experience high stress as a result of illness and disease or other external factors, such as transportation, weaning and social or environmental changes. Past research has shown that serum-based bioactive proteins help to manage symptoms and stress associated with illness. Increased survival and performance of pigs and calves suffering from respiratory and intestinal disease has been reported in numerous studies. In humans with irritable bowl syndrome, serum-based bioactive proteins reduced the number of symptomatic days. Although there are data supporting the use of bioactive proteins in farm animals and humans, the data in horses are limited. A recently reported study by Dr. Josie Coverdale from Texas A&M University demonstrated improved stride length at the walk and trot in regularly exercised Quarter Horse geldings that were given serum-based bioactive proteins for 14 days. As the science in this area is strong in other species, one would expect to see additional equine studies published in the near future. The value of bioactive proteins in supporting health and reducing the effects of disease are well documented in animal agriculture and human research; however, the horse industry is only beginning to tap into these benefits. The future in this area is bright with the potential to set a new standard for horse health and performance. MeV

For more information: Dr. Hammer is the director of the Equine Science program at North Dakota State University and also serves as the State Horse Extension Specialist.

Diffusion of mepivacaine from tendon sheaths Injecting the digital flexor tendon sheath with mepivacaine at the standard dose results in sufficient concentration for analgesia only in the digital flexor tendon sheath. There was no clinically relevant diffusion to adjacent synovial structures, according to a study by researchers from Ghent University in Belgium. The researchers wanted to evaluate the extent of diffusion of mepivacaine to adjacent synovial structures following intrasynovial injection into the digital flexor tendon sheath. Eight horses with no clinical or radiographic orthopedic abnormalities were included in the study. Under general anaesthesia in lateral recumbency, each horse had synoviocentesis of the digital flexor tendon sheath performed on the uppermost forelimb and hindlimb. At the same time, venous blood samples were obtained. A standard dose of mepivacaine (1 mL/50 kg) was injected into the same limbs from which synovial fluid had been sampled. Samples of synovial fluid were then aspirated from the treated tendon sheaths as well as the metacarpophalangeal/metarsophalangeal joint, proximal interphalangeal joint, distal interphalangeal joint and navicular bursa in the injected limbs and the contralateral metacarpophalangeal/metatarsophalangeal joint 15 minutes (forelimb) and 60 minutes (hindlimb) post-injection with blood samples at the same points. The protocol was repeated two weeks later except that the forelimb sites were sampled at 60 minutes and the hindlimb sites at 15 minutes. All tendon sheath injections resulted in mepivacaine concentrations within synovial fluid well above those required for analgesia. Very low mepivacaine concentrations were found in all adjacent synovial structures sampled, and even the highest of these was well below a clinically relevant level. The concentrations in adjacent structures were all higher at 60 minutes post-injection than at 15 minutes, with the exception of the navicular bursa. There were no statistically significant differences between the concentrations in each adjacent synovial structure. Concentrations in blood were also below clinically significant concentrations at both time points. A limitation to the study, the researchers said, was that it was MeV performed in sound horses, so more studies are needed.

For more information: Jordana M, Martens A, Duchateau L, Haspeslagh M, et al. Diffusion of mepivacaine to adjacent synovial structures after intrasynovial analgesia of the digital flexor tendon sheath. Equine Vet J. 2015 Mar 31. doi: 10.1111/evj.12447. [Epub ahead of print] ModernEquineVet.com | Issue 7/2015

15


infectious disease

EIV increases in

older horses In some instances equine influenza vaccine may have provided suboptimal protection to horses that received vaccination. K a t h l e e n

A surveillance program detected an increase in equine influenza virus (EIV) among older horses and previously vaccinated horses compared with earlier surveillance data. Based on the study results, lead

16

Issue 7/2015 | ModernEquineVet.com

O g l e

investigator Nicola Pusterla, DVM, PhD, DACVIM, of the Department of Medicine and Epidemiology, School of Veterinary Medicine at the University of California, Davis, said that in some instances equine influenza vaccine may have provid-

ed suboptimal protection to horses that received the vaccine. Equine influenza virus is a prevalent respiratory pathogen, and it is easily spread through fomites, droplets and aerosoles. “What truly characterizes these pathogens is their short reproductive cycle, hence they are highly contagious because they spread rapidly,” Dr. Pusterla said. “Depending on the susceptibility of the population, the morbidity can be as high as 90% while the mortality is fortunately relatively low.” It has a high financial impact to the equine industry leading to the cancellation of shows and quarantine of horses to prevent transmission and spread, he said. For the surveillance study, which was funded by Merck Animal Health, Dr. Pusterla and colleagues collected samples of nasal secretions from horses with acute fever (≥ 101.5⁰ F) and respiratory signs (lethargy, nasal discharge, coughing) from 239 veterinary practices in 38 states from March 2010 to November 2013. The samples were shipped overnight to a laboratory where they were processed using quantitative testing with polymerase chain reaction (qPCR). Investigators then

©shutterstock/Frank Fennema

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compared their results to those obtained from an earlier EIV surveillance study, conducted March 2008 to February 2010. Of the 2,605 horses enrolled in the study, 230 were found to be qPCR-positive for EIV. The infected horses ranged in age from 3 weeks to 24 years (median, 6 years). A questionnaire was used to collect data about each horse’s vaccination status including time of vaccination and type of vaccine used. The vaccine brand and manufacturer were not included. Of the 230 tested positive for EIV, 84 had been previously vaccinated, 15 were unvaccinated and the status was unknown in 131 horses. “For those who have ever dealt with questionnaires, sometimes it’s difficult to gather appropriate information. When it came to vaccination, unfortunately 50% to 60% of the questionnaires had ‘unknown’” Dr. Pusterla said at the American Association of Equine Practitioners annual meeting. Still, the investigators found that the same percentage of horses were found qPCR-positive for EIV in both the control and previously vaccinated horse groups. Of the horses known to receive a vaccination, 69 received a killed adjuvanted EIV vaccine, 5 received a modified-live EIV vaccine, and for 10 horses, the type of vaccine was not listed, Dr. Pusterla reported. “If you look at vaccine type used, the horses were predominantly vac-

Equine influenza virus is a prevalent respiratory pathogen, and it is easily spread through fomites, droplets and aerosoles. cinated with a killed adjuvanted vaccine. There was no significant difference in the use of the vaccine when we compared control versus EIVpositive horses,” Dr.Pusterla said. “The majority of the horses had been vaccinated recently, less than 6 months versus 6 to 12 months or over 12 months,” he added. When the results of the two surveillance programs were compared, the investigators found that horses testing positive for EIV in 2010–2013 tended to be older—5 to 10 and 10 to 15 years of age—than the horses that tested positive in 2008–2010. In the earlier surveillance program, 2008-2010, 50% of the horses testing positive for EIV were younger than 5 years of age. “When we looked at the two different pairs, we found that in the

more contemporary set we are dealing with older and previously vaccinated horses. It's also interesting to see that within these, we see horses that predominantly have been vaccinated less than 6 months,” he said. Sequence analysis of the selected strains revealed the EIV isolates were clade 1 sublineage. Dr. Pusterla explained that clade 1 viruses are present in North America, Europe, South Africa, Japan and Australia. Clade 2 viruses are seen primarily in Europe, China, as well as India. However, Dr. Pusterla said, it is only a matter of time before clade 2 is active in the United States. Dr. Pusterla also cited surveillance data from the Office International des Epizooties, which has reported on outbreaks of clade 1 and clade 2 in previously vaccinated animals. “This brings the point and the possibility with vaccine available in North America, that in some instances we are dealing with suboptimal protection. So I urge the industry to really consider including epidemiologically relevant strains when it comes to equine influenza,” Dr. Pusterla said. He recommended including a strain that is present and causing clinical disease in previously vaccinated animals, a strain that causes moderate to severe clinical disease, and a strain that is genetically and antigenically different from what is included in a killed MeV adjuvanted vaccine.

For more information: Pusterla N, Kass PH, Mapes S Voluntary surveillance program for equine influenza virus in the United States from 2010 to 2013. J Vet Intern Med. 2015 Jan;29(1):417-22. doi: 10.1111/jvim.12519. Epub 2015 Jan 14. http://www.ncbi.nlm.nih.gov/pubmed/25586234 ModernEquineVet.com | Issue 7/2015

17


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