The Modern Equine Vet - October 2020

Page 1

The Modern

Equine Vet

Safer Semen Extenders

Vol 10 Issue 10 2020

Ask the Infectious Disease Expert Does My Horse Need EIV Vaccine? Ask the Nutritionist Best Diet for Vitamin E Supplementation A Pain in the Rear PRP Injection Tips




4 Amikacin/Penicillin Saw Enhanced

Antimicrobial Activity in Semen Extender Cover: Shutterstock/anakondasp


What Do You Recommend to Supplement Vitamin E Levels?................................................ 3 ASK THE INFECTIOUS DISEASE EXPERT

Should My Horse Get Equine Flu Vaccine?................................................................................ 9 ORTHOPEDICS

Assessing the Back Can Be a Pain in the Rear.......................................................................10 PRP in Practice: Tips on Safe Injection Techniques.............................................................16 NEWS

Avoiding Repeat Needle Sticks in Sick Foals..........................................................................18 AAEP Publishes Lyme Disease Guidelines...............................................................................18 Should You Prescribe Omeprazole with Phenylbutazone?..............................................19 AVMA Report: Antimicrobial Resistance in Animals ...........................................................19 ADVERTISERS Purina Sponsored Content.........................................3 Zoetis..............................................................................5 Merck Animal Health..................................................7 Merck Animal Health Sponsored Content..............9 American Regent Animal Health/Adequan.........11

Shanks..........................................................................12 AVMA PLIT....................................................................13 AAEVT............................................................................15 Equine Regenerative Medicine & Orthobiologics Summit............................................17

The Modern

Equine Vet SALES: Matthew Todd • Matthew Gerald EDITOR: Marie Rosenthal ART DIRECTOR: Jennifer Barlow CONTRIBUTING WRITERS: Paul Basillo • Adam Marcus 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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LEGAL DISCLAIMER: The content in this digital issue is for general informational purposes only. PercyBo Publishing Media LLC makes no representations or warranties of any kind about the completeness, accuracy, timeliness, reliability or suitability of any of the information, including content or advertisements, contained in any of its digital content and expressly disclaims liability of any errors or omissions that may be presented within its content. PercyBo Publishing Media LLC reserves the right to alter or correct any content without any obligations. Furthermore, PercyBo disclaims any and all liability for any direct, indirect, or other damages arising from the use or misuse of the information presented in its digital content. The views expressed in its digital content are those of sources and authors and do not necessarily reflect the opinion or policy of PercyBo. The content is for veterinary professionals. ALL RIGHTS RESERVED. Reproduction in whole or in part without permission is prohibited.


Ask the



Ask the Nutritionist is a monthly column featuring questions answered by PhD equine nutritionists and sponsored by Purina Animal Nutrition. Have a nutrition question you want to see featured? Email Marie Rosenthal. For clinics looking for specific nutritional advice, visit

What do you recommend feeding a horse with low blood levels of vitamin E? Vitamin E is one of the body’s most potent antioxidants affecting immune function, the neuromuscular system and reproduction. The best dietary source of vitamin E is growing green grass, but since many horses do not have consistent pasture access, vitamin E supplementation is needed. Being fat-soluble, vitamin E will be stored for utilization during periods of low intake. A normal adult horse previously consuming adequate vitamin E can reportedly go up to 18 months without presenting noticeable signs of deficiency. This was good for horses in the wild as they went from grazing green forages in the spring and summer to grazing dead, standing dry matter in the fall and winter. With 90% vitamin E storage being in adipose tissue, body condition will affect vitamin E body stores. Serum α-tocopherol level ≥2 ug/mL is considered normal1; however, there is wide variation in single-sample results, and some horses with low vitamin E levels show no apparent clinical effects. Factors affecting serum α-tocopherol concentrations include breed, age, number of samples, diet, sampling time in relation to feeding, physical conditioning, collection method and sample storage before analysis. Due to individual variability reported over a 72-hr period, and deficient horses fluctuating between deficient and normal concentrations within a 24-hr period2, multiple samplings (i.e., three per horse) would be ideal. More practical recommendations are to repeat a single sample and average the values if the first sample is marginal (α-tocopherol between 1.5 and 2 ug/mL). Horses with a high suspicion of α-tocopherol deficiency based on clinical signs, but with marginal or normal serum α-tocopherol concentrations, should have at least two samples evaluated at different time points.3 SOURCES OF VITAMIN E There are multiple sources of vitamin E, and not all are equally utilized by the horse nor equally stable in manufactured feed formulations. Both factors should be considered when determining whether to supplement with vitamin E and what supplements to choose. There are multiple reports of natural-sourced vitamin E being more effective in

elevating serum α-tocopherol than synthetic-sourced vitamin E. However, synthetic vitamin E supplementation has consistently maintained serum levels ≥2 ug/mL in healthy horses. Due to the stability, cost-effectiveness and long history of being an effective vitamin E source for normal horses, synthetic vitamin E is a reliable source for feed formulations. Natural-source, more specifically aqueous RRRα-tocopherol, supplementation may be warranted for horses with low serum vitamin E levels despite adequate dietary intake from forage and supplemented feed. This water-soluble α-tocopherol is currently recommended for horses with Equine Motor Neuron Disease (EMND), Neuroaxonal Dystrophy/Equine Degenerative Myeloencephalopathy (NAD/EDM) or vitamin E deficient myopathy.1 This form is not stable in feed formulations and must be provided through a supplement. Current 2007 NRC recommendations of 1 IU/kg BW for maintenance and gestation, 1.6 – 2 IU/kg BW for increasing work levels and 2 IU/kg BW for growth and lactation are adequate in normal, healthy horses. Additional supplementation with water-soluble α-tocopherol at 2 – 5 times NRC recommendations may be warranted in horses with low serum vitamin E levels. Retest horses after three weeks of supplementation. In healthy exercising horses, a high dosage of vitamin E supplementation (10x NRC requirements) was shown to be potentially detrimental to beta-carotene absorption and thus not recommended. Contact a Purina PhD nutritionist for a complimentary consultation through Purina Customer Service, 800-227-8941 or send us a message at

NEW RESOURCE CENTER Visit for clinical nutritional recommendations from Team Purina, free tools and resources to help you support horses in your care.

Finno, C.J. and S.J. Valberg. A Comparative Review of Vitamin E and Associated Equine Disorders. JVIM. 2012; 26: 1251 – 1266. Craig AM, et al. Variations of serum vitamin E, cholesterol, and total serum lipid concentrations in horses during a 72-hour period. Am J Vet Res 1989; 50: 1527 – 1531. Vanschandevijl K, et al. Variation in deficient serum vitamin E levels and impact on assessment of the vitamin E status in horses. Vlaams Diergeneeskunidig Tijdschrift 2008; 78: 28 – 33.

1 2 3

ABOUT THE AUTHOR Dr. Karen Davison, Ph.D., is a director and nutritionist on the Equine Technical Solutions Team at Purina Animal Nutrition. She enjoys working directly with horses and horse owners to tweak individual feeding programs to help each horse reach its true potential. SPONSORED BY PURINA ANIMAL NUTRITION | Issue 10/2020



Amikacin/Penicillin Semen Extender

Saw Enhanced Antimicrobial Activity in

By Marie Rosenthal, MS The addition of amikacin and penicillin

dent in the Department of Large Animal Clinical Services at the College of Veterinary Medicine. A variety of commercially available semen extenders and several antibiotics are used for this purpose, but Dr. Hernández-Avilés and his group wanted to know whether 2 more narrow-spectrum antibiotics—amikacin and penicillin—would be as effective as other antibiotic types, such as synthetic β-lactams. A 2018 study from his group found that amikacin and penicillin had better antimicrobial activity than new generation antibiotics—synthetic β-lactams or carbapenems—when added to a milkbased semen extender. In that study, they found that both commensal bacteria and certain levels of po-

Source: Dr. Hernández-Aviles

to a commercial semen extender enhanced antimicrobial activity against commensal bacteria without affecting the sperm quality or fertility, according to several studies performed by Camilo HernándezAvilés, DVM, of Texas A&M University. It is normal for the skin of the penis of breeding stallions to harbor nonpathogenic bacteria, and most ejaculates contain some commensal bacteria. However, sometimes ejaculates are contaminated with potentially pathogenic bacteria, usually Klebsiella pneumoniae or Pseudomonas aeruginosa. So, antibiotics are frequently added to inhibit bacterial growth, explained Dr. Hernández-Avilés, a PhD stu-

Collecting a sample. This stallion's semen was contaminated with both commensal and pathogenic bacteria, before and after dilution with INRA-96 extended with added amikacin and penicillin.


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Oertly. et al. The accuracy of Serum Amyloid A in determining early inflammation in horses following long-distance transportation by air. AAEP Proceedings, 2017 460-461.

All trademarks are the property of Zoetis Services LLC or a related company or a licensor unless otherwise noted. Stablelab is a registered trademark of Epona Biotech Limited, used under license. Š 2020 Zoetis Services LLC. All rights reserved. STB-00074

Source: Dr. Hernández-Avilés


A culture taken from raw semen of a stallion with bacterial urethritis. The bacteria obtained included a mixed growth of both Escherichia coli and Klebsiella pneumoniae.

tentially pathogenic bacteria were completely eliminated from semen when the extender contained a conventional dose of both amikacin and penicillin. Yet, when the ejaculates were contaminated with high levels of P. aeruginosa¸ the addition of amikacin and penicillin did not offer any advantage over the other antibiotics tested. From that study, they concluded that none of the antibiotic additions affected the sperm quality, and the use of amikacin and penicillin in a milk-based extender provided “better control of commensal bacterial populations when semen was cooled.” In their current study, they wanted to determine the best doses to inhibit bacterial growth without affecting the sperm motion characteristics and plasma membrane intactness of semen diluted with a very popular casein-based extender in North America and Europe, INRA-96. This semen extender is formulated with certain antibiotics that are added at lower concentrations than in other commercially available semen extenders. “The INRA-96 extender is a very effective medium to preserve semen quality during cooled storage; however, we have some field reports of heavy growth of pathogenic bacteria when this extender is used for cooled storage of semen,” he explained. So they wanted to know if adding amikacin and penicillin to this casein-based extender could offer better control of bacterial growth without affecting sperm quality. 6

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A culture plate obtained from cooled stored semen diluted with INRA-96 extender with added amikacin and penicillin and looked at (3,000 ug/ mL–3,000 IU/mL).

They collected semen from multiple stallions and then diluted it with INRA-96 extender to 3 treatment groups: 1. amikacin/penicillin G, 2. ticarcillin clavulanate (both at standard doses), and 3. no additional antibiotics and served as a control. They checked the sperm quality after 30 minutes and then again after 24 hours of cooled storage. There was less growth in the INRA-96 plus amikacin/penicillin group than the other 2 groups, he said. “We found that after 30 minutes of exposure or 24 hours of cooled storage, amikacin/penicillin added to the INRA-96 extender significantly reduced the number of commensal bacteria as compared with ticarcillin clavulanate or the extender with no added antibiotic,” he explained, and the sperm quality did not appear to be affected. The amikacin they were using was expensive, so they wanted to switch to a less expensive product by another company, and repeated the experiment to ensure that the second amikacin was also effective, substituting the less expensive amikacin with the more expensive product in a fourth group. “We concluded that the amikacin products yielded similar values for semen quality and bactericidal effectiveness versus commensal bacteria, but again, we're still having some commensal bacterial growth,” Dr. Hernández-Avilés said.


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“We decided to do a dosetitration experiment in which we wanted to find the most effective dose of amikacin/penicillin to completely eliminate commensal bacteria growth, without affecting sperm quality,” he said. They collected semen from multiple stallions, which was diluted with the INRA-96 extender and looked at 5 different amikacin/penicillin dosing group: • a standard dose of 1,000 µg/ mL of amikacin and 1,000 IU/ mL of penicillin, • or 2, 3, 4, 5 times this standard dose. They found that with doses of 3,000 µg/mL of amikacin and 3,000 IU/mL of penicillin, “there was a significant improvement on the complete elimination of commensal bacteria as compared with the standard dose or a 2-fold dose,” he said. This improvement was seen at 30 minutes, as well as 24 hours after cold storage. The sperm quality was not affected in any treatment group. “Still you might wonder what could happen with the fertility of semen that has been processed with these types of antibiotics,” he said, so they did 1 more study, in which cooled semen was used to impregnate 11 broodmares. The semen was donated by 1 stallion and was divided into 2 treatment groups: 1. the INRA-96 extender without additional antibiotics, 2. the INRA-96 extender with 5,000 µg/mL of amikacin and 5,000 IU/mL of penicillin added. A pregnancy diagnosis was conducted 14 days after ovulation by ultrasonography. They could not detect any significant differences between both treat-

ment groups in terms of pregnancy rate. “So, based on the results from this study and previous studies from our laboratory, a standard dose of amikacin/penicillin was not completely effective for controlling commensal bacteria or potentially pathogenic bacteria,” he said, but a higher dose was more effective. Because the studies used commensal rather than pathogenic bacteria, the studies are now being done looking at K. pneumoniae and P. aeruginosa contaminants. Doses this high might not be preferred routinely if there are no pathogenic bacteria, because of concerns about resistance, Dr. Hernández-Avilés admitted. However, these 2 organisms can cause bacterial endometritis in mares, and resistance for amikacin is relatively rare in veterinary medicine. In their recent study published in the journal Theriogenology, they included data from 2 stallions whose semen was heavily contaminated with K. pneumoniae or P. aeruginosa. They found that adding amikacin and penicillin to the INRA-96 extender helped to control bacterial growth in the ejaculates from these stallions, without compromising sperm quality. “Amikacin/penicilin—even at high doses—can be considered safe for sperm and fertility and are more effective than new-generation antibiotics when we are faced with commensal bacteria or some potentially pathogenic bacteria,” he said. Dr. Hernández-Avilés presented some of this work at the annual convention of the American Association of Equine Practitioners MeV



in eliminating

bacteria in semen with 3,000 µg/mL of amikacin and 3,000 IU/ML of

penicillin added to the semen extender.

For more information: Hernández-Avilés C, Love CC, Serafini R, et al. Inclusion of supplemental antibiotics (amikacin-penicillin) in a commercial extender for stallion semen: Effects on sperm quality, bacterial growth, and fertility following cooled storage. Theriogenology. 2020;158:209–217. Hernández-Avilés C, Love CC, Serafini R, et al. The effects of antibiotic type and extender storage method on sperm quality and antibacterial effectiveness in fresh and cooled-stored stallion semen. Theriogenology. 2018; 122:23–29. 8

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Infectious Disease Expert This column, brought to you by Merck Animal Health, features insightful answers from leading minds.

What’s the outlook for equine influenza this season, and how can I help my clients understand which horses should get vaccinated?


eason” is the operative word here. Equine influenza virus (EIV) infects horses throughout the year, but cases ramp up between mid-winter and early spring, according to data from the Equine Respiratory Biosurveillance Program.1 The best way to slow the spread of EIV is to ensure horses are properly vaccinated. To help clients understand what’s proper, start by reinforcing the recommendations outlined in the AAEP risk-based vaccination guidelines.2 Second, explain two key points: • EIV is mutating through antigenic drift • Not all vaccines are created equal The Biosurveillance Program data illustrates these points. The program, which our lab conducts in partnership with Merck Animal Health, provides long-term and realtime EIV monitoring. We analyze samples submitted by more than 250 enrolled clinics from across the country to tabulate EIV case numbers and finely dissect the expected and unexpected outcomes of every positive case.

AN EVOLVING VIRUS CALLS FOR EVOLVING VACCINES In early 2010, we observed a pattern of unexpected outcomes: higher numbers of older, vaccinated horses were testing positive for EIV. This led to the hypothesis that the virus

RETHINKING EIV RISK Horses that travel are at increased risk for equine influenza virus (EIV). While clients may be traveling less with their horses during the COVID-19 pandemic, don’t let them get a false sense of security. EIV spread occurs with or without travel. In fact, 45 percent of EIV cases between July and December of 2019 occurred in non-traveling horses, according to data from the Equine Respiratory Biosurveillance Program.1 What’s more, EIV doesn’t discriminate based on age. Between July and December of 2019, Biosurveillance Program data showed the median age of EIV-positive horses was 2 years old, but horses as old as 24 years tested positive.1 Make sure clients understand that vaccination reduces the severity of clinical signs and the amount of EIV shed, hence reducing environmental contamination and risk of EIV spread. Herd immunity is best achieved by semi-annual EIV vaccination, whether horses are traveling or staying at home. Less frequent vaccination intervals will allow horses a greater opportunity to experience EIV, since duration of immunity declines beyond six months from last EIV vaccination.

was slowly mutating and escaping vaccinespecific immunological responses. To determine whether this was due to the introduction of foreign EIV strains or to the natural selection of EIV strains (antigenic drift), a researcher in our lab compared the heterogeneity of circulating wildtype EIV strains in the United States with Ohio ’03 (OIE recommended clade 1 influenza strain). The conclusion: Foreign EIV strains have not been circulating in the United States. Only EIV Florida clade 1 strains have been circulating and have evolved separately from clade 2 strains.3 Your clients may not need all this background, but it is important to make them aware of antigenic drift and its effect on vaccination choices. Tell your clients that EIV evolves like human flu but much slower. EIV vaccine failure occurs when the virus changes at certain immunodominant sites (i.e. sites that are important for the virus to escape the immune response). Therefore, horses should receive an EIV vaccination that has evolved along with the virus to account for the most up-to-date flu strains. Ongoing EIV sequencing through the time of this article reflects that Florida ’13 is representative of current circulating U.S. field strains.4

1 Merck Animal Health and University of California, Davis School of Veterinary Medicine (Nicola Pusterla). Infectious Upper Respiratory Disease Surveillance Program. Ongoing research 2008-present. 2 American Association of Equine Practitioners, Risk-Based Vaccination Guidelines, Equine Influenza., accessed Aug. 31, 2020. 3 Lee K, Pusterla N, Barnum S, Martinez-Lopez B. Is Current Vaccine Failure of Equine Influenza Virus Due to Evolution of Endemic Strains or Introduction of Foreign Strains? AAEP Proceedings. 2019 Vol 65. 4 Merck Animal Health Technical Bulletin, December 2019.

ABOUT THE AUTHOR Dr. Nicola Pusterla, DVM, PhD, DACVIM, DAVDC-Equine is a professor of equine internal medicine and dentistry at the University of California, Davis, School of Veterinary Medicine. His research focus is on equine infectious diseases with an emphasis on molecular epidemiology. Dr. Pusterla also leads the UC Davis Equine Infectious Disease Research Laboratory.


WANT TO ASK A QUESTION? EMAIL THE EDITOR. For more infectious disease-related information, visit | Issue 10/2020



Assessing Back Pain CAN BE A PAIN IN THE REAR M a r i e

R o s e n t h a l ,

Although lower back pain is not typically thought of as a primary cause of lameness in a horse, it can be a source of pain that can affect performance, especially for horses doing barrel racing or dressage, according to Philippe H. Benoit, DVM, MS, DACVSMR, of Cardiff, Calif. And it is kind of a pain in the rear for veterinarians because a precise diagnose can be difficult to ascertain, he said. Typically, lower


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back pain and discomfort have been considered as a compensatory issue caused from hind limb lameness, but issues related to the back and pelvis can be the primary source of the problem. The history doesn’t always help either, because clients often complain that the horse just isn’t “working right.” And the physical examination and flexion during the examinations can be “normal.” It is not unusual to hear the referring veterinarian tell you: “I know this horse is sound,” Dr. Benoit said, “but he does not perform well.” Often, the complaint is a lack of scope, defect of push or poor arc in flight. And there are behavior issues that

Shutterstock/Kobby Dagan

B y

There’s nothing else like it. Over the past 30 years, Adequan® i.m. (polysulfated glycosaminoglycan) has been administered millions of times1 to treat degenerative joint disease, and with good reason. From day one, it’s been 2, 3 the only FDA-Approved equine PSGAG joint treatment available, and the only one proven to. Reduce inflammation Restore synovial joint lubrication Repair joint cartilage Reverse the disease cycle When you start with it early and stay with it as needed, horses may enjoy greater mobility 2, 4, 5 over a lifetime. Discover if Adequan is the right choice. Talk to your American Regent Animal Health sales representative or call (800) 458-0163 to order. BRIEF SUMMARY: Prior to use please consult the product insert, a summary of which follows: CAUTION: Federal law restricts this drug to use by or on the order of a licensed veterinarian. INDICATIONS: Adequan® i.m. is recommended for the intramuscular treatment of non-infectious degenerative and/or traumatic joint dysfunction and associated lameness of the carpal and hock joints in horses. CONTRAINDICATIONS: There are no known contraindications to the use of intramuscular Polysulfated Glycosaminoglycan. WARNINGS: 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. PRECAUTIONS: The safe use of Adequan® i.m. in horses used for breeding purposes, during pregnancy, or in lactating mares has not been evaluated. For customer care, or to obtain product information, visit To report an adverse event please contact American Regent, Inc. at (800) 734-9236 or email Please see Full Prescribing Information at 1 Data on file. 2 Adequan® i.m. Package Insert, Rev 1/19. 3 Burba DJ, Collier MA, DeBault LE, Hanson-Painton O, Thompson HC, Holder CL: In vivo kinetic study on uptake and distribution of intramuscular tritium-labeled polysulfated glycosaminoglycan in equine body fluid compartments and articular cartilage in an osteochondral defect model. J Equine Vet Sci 1993; 13: 696-703. 4 Kim DY, Taylor HW, Moore RM, Paulsen DB, Cho DY. Articular chondrocyte apoptosis in equine osteoarthritis. The Veterinary Journal 2003; 166: 52-57. 5 McIlwraith CW, Frisbie DD, Kawcak CE, van Weeren PR. Joint Disease in the Horse.St. Louis, MO: Elsevier, 2016; 33-48. All trademarks are the property of American Regent, Inc. © 2020, American Regent, Inc. PP-AI-US-0372 02/2020


Click here to watch a video

signal pain. The horse is difficult to ride, resists work, is aggressive or has a bad attitude. And although the rider’s observations are important, “the vet evaluation is always a bit different than the rider’s assessment,” he said. These complaints could very well be a back issue, rather than a hind limb or behavior problem. As with any other issue, a thorough clinical examination is essential and should include full observation and clinical physical palpation, as well as testing and imaging. It can be useful to watch videos of the horse’s performance or training before starting the examination, Dr. Benoit said. Watch them in slow motion, he suggested, and look at the position of the neck and the back, as well as withers elevation and lumbar extension. The horse will often modify its jumping style, maybe leaning a little sideways or off center when sore. The examination should begin with palpation of the neck, withers, thoracic spine and lumbar area,

Video, especially viewed in slow motion, can be a great tool to assess the animal's form during work.

Lifting Large Animals Since 1957


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with a focus on the caudal aspect of the back, starting with a superficial palpation and then gradually a deeper palpation. Look at the conformation and posture of the hind limbs, the shape mass and symmetry of the muscles, joint distention, soft-tissue swelling and weightbearing abnormalities. “Although not usually done during a lameness examination, rectal palpation can provide a lot of information about back and pelvis issues,” Dr. Benoit added. It allows one to palpate the caudal lumbar area, psoas muscles, pelvic 3. bones and other structures that cannot be reached any other way, as well as castration scar tissue, ovary glands and inguinal rings. These structures might be interfering and contributing to back pain. Observing the horse in a circle on hard and soft surfaces at a walk, canter and trot are just as important as when assessing lameness, but again, remember that issues might be subtle. Look at the position of the head and neck, watch for toes dragging on the ground, he suggested. There are tests, such as the surcingle test—which is placed on the horse and tightened—that can enhance a defect of motion or gait asymmetry. Under-saddle

Courtesy of the Dr. P. Benoit

SI Ligt Ventral

Watch the head and neck during work.

evaluation is also important, Dr. Benoit said. Mobilization can help determine range-of-motion issues affecting various segments of the lower back and pelvis. Imaging should be among the last things done during the evaluation, Dr. Benoit said. Too often,

imaging is done early and that becomes the focus of the rest of the examination, rather than the examination directing what imaging is done. "You can get too much information about nothing, and you don’t know what to do next,” he said. “The thorough exam starts with localizing the back pain.”

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Epaxial joint disease of the lumbar facets

• “tight” longissimus and gluteus muscles on palpation, • walk or jog with hind limbs in abduction, • poor flexion of the long back or extension, • asymmetry, hind quarters shifts to the inside on the circle and drags the hind limb toes, • negative flexion of hind legs, but limited range of motion

Radiography, ultrasonography

Sacroiliac joint diseases

• posture: hind limb in adduction • lean on their hindquarters again stall or wall • contracted and sore psoas • lumbosacral and coxofemoral joints in flexion • tight low-back muscles, longissimus and gluteus medius

Nuclear scan, ultrasonography

• Involves discs and surrounding structures • Passive flexion of hind limbs can be difficult to perform • Difficulty rotating his pelvis • At canter: poor range of flexion/collection • Rider reports lack of push • On lunge line: counter canter • Can be difficult to flex or elevate limbs

Bone scan, radiographs, transrectal ultrasonography

Illium wing/pelvis fracture

• Acute: Significant lameness • Movement difficult • Difficult to pick up limb • Strong spasm of the gluteus medius • Transrectal palpation: bilateral psoas muscle tension and soreness • Very hesitant to move and position opposite side limb in adduction

Bone scan, ultrasonography

Hip joint disease

• Lame • Bilateral pain • Lack of push, short-sided trot and canter, but may warm up from this discomfort • Hind limbs may travel more in abduction

Bone scan, ultrasonography, radiographs limited to young horses and foals

Trochanteric bursa

• Moderate lameness • Local pressure is painful

Bone scan, ultrasonography, radiographs, but very difficult to see

Lumbosacral pain

Radiographs, ultrasonography and bone scans can all be helpful depending on the differential, according to Dr. Benoit. Depending on the issue, Dr. Benoit tends to treat these problems with injections of medications and regenerative products as well as complementary treatments, such as massage, physiotherapy, shockwave treatments, chiropractic or acupuncture. 14

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Just as humans no longer rest typically for low back pain, stall rest for horses is not normally considered for lower back pain, except for traumatic injury, such as fracture. Back and pelvic pain can be a reason for mild discomfort, but without proper assessment and management, it can progress to poor performance, intense pain and become a chronic issue for the horse. MeV


PRP IN PRACTICE: Tips on safe injection techniques P a u l

Platelet-rich-plasma (PRP) has increasingly

been used in equine medicine for the treatment of joints, bursae and soft tissue injuries. During the past 5 years, A. Kent Allen, DVM, ISELP, and his colleagues at Virginia Equine Imaging, have used PRP in more than 400 horses totaling about 800 individual joints, and he’s confident in the beneficial effects of PRP in equine practice. He recently passed along some helpful tips dur-


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B a s i l i o ing the Equine Regenerative Medicine and Orthobiologics Online Summit

Volume, frequency, and gain

“You want to be comfortable with ultrasound-guided injections and have a plan for reducing the pain of the needle passage,” Dr. Allen said. “Whether it’s a regional nerve block or a skin block, come up with a plan beforehand on how you can reduce the pain of this injection technique.” It is crucial to avoid over-pressurizing the lesion, joint, or bursa by keeping an eye on the volume that is being injected. If there is any resistance on the plunger of the syringe or if tissue separation starts to become evident, back off and perhaps draw the syringe out slightly. “Those situations will look very much like a flarelike syndrome, but they come from pressurizing that joint and structure,” he added. For the ultrasound probe, make sure it is positioned well enough to easily see the needle passage. For guided injections, the frequency should be set a little lower and the gain should be set a little higher than what practitioners typically set for ultrasound imaging. “That accentuates the needle,” Dr. Allen explained. “The needle is passing in the thin plane of the probe, which is only about 2 mm thick. You have to stay in that plane, so anything that helps you see that a little better is something you need to do.” For sacroiliac injections, he also recommended clipping the haircoat—particularly in the winter. If the PRP is not flowing easily into the lesion, scarring that was not appreciated beforehand may be giving the needle a bumpy ride. “You think you’re going into a fairly hypoechoic lesion and the PRP is going to flow easily, but once you get the needle in there you may find that it’s not happening,” he said. “Always be prepared to have a secondary plan for depositing the PRP perilesionally.” Using a reasonable needle gauge (eg, 20-gauge) with the horse in a non-weightbearing stance, it’s

Shutterstock/Click and Photo

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possible to put a small amount of air into the syringe to see the air bubbles flow, which will help you track where the injection is going. “Sometimes if you’re doing a tendon with a fairly long lesion, this allows you to see where you’ve gotten the PRP in and where you have not,” Dr. Allen explained. “Then you can reposition the needle appropriately.”

Recheck and plan

To monitor the success of the treatment, Dr. Allen usually rechecks the horse in 30-day intervals to assess the progress. “If it didn’t work, you may want to consider another PRP injection or you may want to rethink your treatment plan,” he said. A structured rehab plan is also important for the success of the treatment. Dr. Allen recommends keeping the horse quiet via sedation on a small paddock turnout. For neck and back lesions, improvement can be monitored by checking in with trainers and riders to see if the horse is tripping less or appears to be comfortable.

Contraindications Concurrent NSAID use should be avoided with PRP injections. In human medicine, good evidence has shown that naproxen affects the quality of PRP treatment. “You’ll want to talk to the client beforehand if you’re doing a PRP injection,” Dr. A. Kent Allen said. “Have the receptionist ask the owner if the horse is on any NSAIDs and have them ask the owner to discontinue them. I prefer a week [NSAID washout period] before and after PRP injections.” A similar approach should be taken with corticosteroids. In an ideal world, Dr. Allen would like to see a horse go off corticosteroids for about 30 days, but that is not always feasible. Infections are rare with PRP injections, but a sterile technique with sleeve covers can decrease the risk.

“It is not uncommon to see significant filling of the lesion at 30 to 60 days,” he said. “The horse still won’t be able to go back to full work despite the tissue appearance, and it will still need the standard term of rehabilitation. Don’t be fooled by that. If good things are happening in that lesion, it doesn’t mean the horse still doesn’t need an appropriate rehab time frame.” MeV


Avoiding Repeat Needle Sticks in Sick Foals The push-pull technique is an acceptable method for obtaining blood samples for venous blood gas analysis in foals and avoids repeated needle sticks, according to a recent study. A manual packed cell volume should be performed in place of hematocrit measurement, researchers added. This study compared venous blood gas parameters from samples collected by a push-pull technique through a jugular catheter with those sampled by direct jugular venipuncture in 17 hospitalized foals. Three different techniques for drawing a blood sample from a catheter were reviewed: the discard, the reinfusion, and the push-pull methods. The push-pull technique avoided the loss of blood associated with the discard method and reduced the risk of contamination associated with the reinfusion method, they said. A 10 mL syringe was used to aspirate a volume

of blood equal to 3 times the dead space volume of a 16G catheter and extension set (total 2.4 mL). This was immediately reinfused into the vein without disconnecting the syringe. This procedure was repeated 3 times before connecting a 1 mL heparinized syringe to collect venous blood. A 20G 1-inch needle and 1 mL syringe were used to obtain a blood sample from the contralateral jugular vein. All samples were analyzed with an automated blood gas analyzer within 10 minutes of collection. There was a high level of agreement between the results obtained by the 2 sampling methods at both 0 and 24 hours for almost all parameters except hematocrit and PVO2 values, the researchers found. This method would also be appropriate for electrolytes, glucose and lactate in sick neonatal foals. The project was funded by a research fund (RFF) of the University of Naples Federico II. MeV

For more information: Del Prete C, Lanci A, Cocchia N, et al. Venous blood gas parameters, electrolytes, glucose and lactate concentration in sick neonatal foals: direct venipuncture versus push-pull technique. Equine Vet J 2020 [Epub August 8].

AAEP Publishes Borrelia burgdorferi Infection and Lyme Disease Guidelines The American Association of Equine Practitioners (AAEP) published comprehensive guidelines to assist practitioners with identification, diagnosis and control of Borrelia burgdorferi infection and Lyme disease, an important tickborne disease of horses in the northeastern United States and beyond. “Borrelia burgdorferi infection is common in horses residing in Lyme endemic areas and the geographic range for exposure appears to be increasing,” said co-author Sally DeNotta, DVM, PhD, DACVIM. “Despite the high prevalence of exposure and seropositivity to B. burgdorferi in horses residing in endemic regions, confirming clinical Lyme disease remains a diagnostic challenge. We hope these guidelines help clear up confusion and provide useful information to assist equine veterinarians with the diagnostic approach and clinical management of horses suspected of having Lyme disease.” The guidelines discusses which horses are at risk, clinical signs and recommendations for diagnostic testing. Several key take aways are: • Serology alone should not be viewed as a stand18

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alone test for Lyme disease because it only confirms exposure to B. burgdorferi or that the horse was vaccinated. • Some exposed horses do not exhibit clinical signs, but routine screening is not recommended. • None of the available seroassays can differentiate exposure to B. burgdorferi from clinical Lyme disease. • The magnitude of antibody titer does not correlate with the likelihood of clinical disease. The Borrelia burgdorferi Infection and Lyme Disease Guidelines, available as a PDF file, was authored for the AAEP’s Infectious Disease Committee by Thomas J. Divers DVM, DACVIM, DACVECC and Dr. DeNotta. The guidelines were reviewed and approved by the AAEP Infectious Disease Committee and board of directors. MeV VIEW the Borrelia burgdorferi infection and Lyme Disease Guidelines or save them to your mobile device for future reference here.

Should You Prescribe Omeprazole with Phenylbutazone? Although concurrent omeprazole when prescribing phenylbutazone reduced the severity of equine gastric ulcer syndrome (EGUS), caution should be exercised when coprescribing phenylbutazone and omeprazole in horses, especially with a concurrent change in management, a recent study found. The researchers did the study because many practitioners prescribe omeprazole concurrently with phenylbutazone to reduce the development of EGUS, but the efficacy and safety of this practice was not really known. They decided to evaluate the effect of omeprazole on phenylbutazone-induced EGUS in adult horses. The researchers divided 22 horses with equine glandular gastric disease (EGGD) and equine squamous gastric disease (ESGD) scores ≤2 into 3 groups: 1. phenylbutazone group (8 horses) received 4.4 mg/kg of oral phenylbutazone every 12 hours; 2. phenylbutazone+omeprazole group received the same phenylbutazone dose plus 4 mg/kg of oral omeprazole every 24 hours (8 horses); and 3. t he control group (CON) consisted of 6 horses.

The horses were treated for up to 14 days and gastroscopy was performed every 7 days. A complete blood count was performed at the beginning and end of the study period. Five horses did not complete the trial due to intestinal complications, 3 in the phenylbutazone+omeprazole group and 2 in the phenylbutazone group. Median EGGD score increased in the phenylbutazone group compared with phenylbutazone+omeprazole group over the study period. No difference was seen in ESGD scores between the 2 treated groups. Serum albumin concentration decreased in the phenylbutazone group compared with the CON group over the course of the study. There was no significant difference in albumin concentration between the phenylbutazone+omeprazole group and the CON group. In the phenylbutazone+omeprazole group, 6 of 8 horses developed intestinal complications, compared with 2 of 8 in the phenylbutazone group and none in the CON group. These complications were fatal in 2 of the horses in the phenylbutazone+omeprazole group. MeV

For more information: Ricord M, Andrews FM, Yñiguez FJM, et al. Impact of concurrent treatment with omeprazole on phenylbutazone-induced equine gastric ulcer syndrome (EGUS). Equine Vet J. 2020 [Epub ahead of print July 22].

AVMA Report: Antimicrobial Resistance in Animals Antimicrobial resistance presents a growing challenge for veterinarians and is a global One Health issue. Slowing and limiting the emergence and spread of antimicrobial resistance requires widespread engagement from across the One Health spectrum, especially among leaders in veterinary medicine, animal owners and public health. “Veterinarians are at the forefront of fighting antimicrobial resistance in animals and have a critical role to play in the overall health of animals, humans and the environment,” said Douglas Kratt, DVM, the AVMA president. “The AVMA is committed to the judicious therapeutic use of antimicrobials and promoting antimicrobial stewardship in veterinary practices.” The American Veterinary Medical Association issued a new report that examines bacteria of concern and describes actions that can help veterinarians and their teams, clients, producers and breeders slow and limit the emergence and spread of antimicrobial resistance. “The AVMA will continue to monitor for trends in

antimicrobial resistance to ensure that veterinarians have the tools they need to make the best stewardship decisions for their patients.” The report was developed by the AVMA Committee on Antimicrobials with the assistance of many species experts as volunteers—a group of nearly 50 microbiologists, epidemiologists and species experts. The report includes easy-to-review summaries of antimicrobial resistant bacteria affecting dogs and cats, horses, cattle, swine, sheep and goats, chickens and turkeys, and fish and shrimp. The report also includes resistance profiles for each of the bacteria identified in the report. “This report is a practical reference guide for veterinarians to use when making therapeutic decisions for their patients,” said Paul Plummer, DVM, one of the lead authors of the report. MeV FOR A COPY OF THE REPORT, click here. | Issue 10/2020


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