The Modern Equine Vet June 2016

The Modern

Equine Vet www.modernequinevet.com

Treating

Gastroplenic Entrapment

Vol 6 Issue 6 2016

Enteroliths How good is your arthrocentesis technique?

Genetic susceptibility to sarcoids?

Table of Contents

colic:

A tale of

4 two entrapments treating GLE and EFE Cover photo: Shutterstock/anjajuli

Lameness

How accurate is your arthrocentesis technique?...........................................................8 Technician Update

Exploratory laparotomy and enterotomy for enterolith removal..............................................................................11 oncology

Do horses have genetic susceptibility to sarcoids?.................16 News

Modern horses run differently than ancient ancestors.......3 Oh, those aging tendons................................................................10 The Irish take liver fluke survey..................................................15 Auburn gets new standing CT........................................................18 Oral glucose tests repeatable in ponies..................................19 advertisers Shanks Veterinary Equipment.................................. 3 Merck Animal Health.................................................. 5

Standlee Premium Western Forage......................... 7 AAEVT............................................................................15

The Modern

Equine Vet Sales: Matthew Todd • ModernEquineVet@gmail.com Editor: Marie Rosenthal • mrosenthal@percybo.com Art Director: Jennifer Barlow • jbarlow@percybo.com contributing writerS: Paul Basillo • Kathleen Ogle 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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News

Modern Horses Run Differently Than Ancient Ancestors mammals can switch between stiff-backed and flex-backed running as they increase in speed. This could be one potential model for the evolution of specialized stiff-backed running in horses. This study reveals a new insight into a famous case-study of locomotor adaptation. “The findings are significant because they show how the backbone—a relatively understudied part of the anatomy—can provide new perspectives on locomotor transitions,” Dr. Jones said.

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Shutterstock/Olga_i

Modern horses reach top speeds using a special running gait in which they hold their back stiff as they move. Researchers found that tiny fossil ancestors of modern horses may have moved quite differently than their living counterparts.

Dating back more than 50 million years, the oldest horse ancestors were no bigger than a house cat.

The researchers suggest that the stiff-backed gait of modern horses likely evolved to save energy while running as horses evolved into larger animals.

“For over a century, researchers studied the feet of fossil horses to explain how they evolved features specialized for running,” explained Katrina Jones, PhD, a post-doctoral researcher in Harvard's Museum of Comparative Zoology, "but little is known about how the backbone might be involved in this famous transition.” Four-legged mammals tend to move their lower back during running to help increase speed and regulate breathing. But horses are unusual because they restrict the motion of their lumbar spine to a single joint near their rump.

To understand the evolution of the back in fossil horses, Dr. Jones first examined the anatomy and mobility of the spine in modern horses. The shape of the vertebral joints help determine how much motion occurs at each joint. Armed with this information, Dr. Jones then measured the shape of vertebral joints in 16 species of fossil horses spanning their full size and age range.

She found that small fossil horses, such as Hyracotherium (the 'dawn horse'), had quite different anatomy of the vertebral joints than their modern equivalents. This anatomy suggests more mobility was possible in the middle and lower portions of their back. Anatomy of these joints was also linked to body size; evolutionary branches which evolved greater size tended to display more restrictive joints.

Dr. Jones hypothesizes that stability of the backbone evolved as a response to the mechanical challenge of large size in horses. “The energy required for a large animal to move at high speed can be extreme, so increasing running efficiency by minimizing motions of the trunk makes sense,” she said, speculating that certain ancient horses may not have been running in the same way as modern horses. Some living

Lifting Large Animals Since 1957

For more information: Jones KE. New insights on equid locomotor evolution from the lumbar region of fossil. Proceedings of the Royal Society B: Biological Sciences. 2016; 283 (1829): 20152947 DOI: rspb.2015.2947 10.1098/

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colic

two entrapments A tale of

B y

shutterstock/anjajuli

Gastrosplenic entrapment

(GLE) and epiploic foramen entrapment (EFE) are fairly small slices of the overall colic pie. As such, the literature to determine whether certain diagnostic findings can help differentiate between the two is light, as is whether the complications and short-term survival associated with each type are similar.

This was the impetus for Isabelle Kilcoyne, MVB, DACVS, of the William R. Pritchard Veterinary Medical Teaching Hospital

at University of California, Davis, and her colleagues to investigate whether GLE would have similar clinical presentation and diagnostic results as EFE, and whether GLE would be associated with a better short-term survival.

The Population

The retrospective study began with horses that had a definitive diagnosis of GLE or EFE based on intraoperative findings of necropsy at the teaching hospital during

P a u l

B a s i l i o

the past 20 years.

“We also looked through the records and pulled the cases that presented for colic during that time and reviewed the signalment for those horses,” Dr. Kilcoyne said here at the 61st Annual AAEP Convention in Las Vegas. “We found 9,755 horses that were examined because of colic during that period.

There were 43 horses with GLE and 73 with EFE in that group.”

Presentation

Tennessee Walking Horses and horses aged 8-12 years were overrepresented in the GLE group, and Thoroughbreds, warmbloods, Morgan horses and horses aged 13-20 years were overrepresented in the EFE group. These findings were significantly different than the overall colic population.

“Contrary to a lot of other studies, we did not find an association between cribbing and GLE

Anatomy Lesson The gastrosplenic ligament is a thin, broad mesenteric band that extends from the greater curvature of the stomach to the cranial edge of the spleen. The exact role of the ligament isn’t exactly known, but it is thought to provide some structural support for the abdominal viscera. It most commonly involves the small intestine, but rare cases have shown the large intestine entrapped within the ligament.

The epiploic foramen is an opening in the omental bursa that 4

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measures 4-6 cm and separates the omental bursa from the rest of the abdominal cavity. The borders of the epiploic foramen include the caudate process of the liver and the portal vein. Recently, the literature has described a more significant role attributed the gastropancreatic fold that forms the dorsal and caudoventral borders of the foramen.

Entrapment typically occurs from left to right.

Safety In Numbers Some dewormers claim just one dose of their product is the best way to deworm your horse, but that’s simply not true.

Demand Safety: You won’t find a laundry list of warnings and precautions on the PANACUR® (fenbendazole) POWERPAC label because fenbendazole has a unique mode of action that makes it safe for horses of all ages, sizes, and body conditions.

Demand Efficacy: PANACUR® POWERPAC is the only dewormer FDA approved to treat ALL STAGES of the encysted small strongyle.1 Other dewormers miss a critical stage, EL3, which can account for up to 75% of the encysted small strongyle burden. Plus, it’s the best choice for treating ascarids — which are not just a problem in young horses!

So when it comes to which dewormer to trust, don’t forget there’s safety in numbers.

Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism.

Do not use in horses intended for human consumption. When using PANACUR® (fenbendazole) Paste 10% concomitantly with trichlorfon, refer to the manufacturers labels for use and cautions for trichlorfon.

1

PANACUR® (fenbendazole) POWERPAC Equine Dewormer product label.

The Science of Healthier Animals 2 Giralda Farms • Madison, NJ 07940 • merck-animal-health-usa.com • 800-521-5767 Copyright © 2016 Intervet Inc., d/b/a/ Merck Animal Health, a subsidiary of Merck & Co., Inc. All rights reserved. 3290 EQ-PC-FP AD

colic

Take-home Points Horses with EFE were more likely to be tachycardic and have hyperlactatemia vs those with GLE. EFE and GLE have a similar favorable short-term survival of surgery.

Middle-aged geldings seem to be predisposed to both types of colics.

Prior colic surgery may increase the risk of EFE. The findings of the study emphasize the increased sensitivity of ultrasound for the detection of small intestinal lesions compared with the presence of nasogastric reflux or rectal findings. or EFE,” she said. “This was likely due to the retrospective nature of the study.”

Dr. Kilcoyne’s study did show that horses in the EFE group were significantly more likely to have had a history of prior colic surgery than horses in the GLE group.

“Horses with EFE had a significantly higher heart rate than those in the GLE group,” she noted.

“That could potentially be caused by pain, but we can’t draw that conclusion because pain was not scored in our study.”

In addition, systemic lactate and peritoneal lactate were both significantly higher in the EFE group, which may indicate that these horses were more systemi-

cally compromised. The proximity of the epiploic foramen to the liver and the pancreas could potentially have secondary effects on those organs and may impact the clinical presentation.

“It was interesting to note that only a small amount in both groups presented with nasogastric reflux,” Dr. Kilcoyne said. “Likewise, small intestinal involvement was only detected in 60% of the cases on rectal examination. Ultrasound, however, showed 92% of the GLE horses and 90% of the EFE horses had evidence of small intestinal distention. The value and sensitivity of this diagnostic modality should lead equine practitioners to perform it in all of their colic cases.”

Treatment

Of the 43 horses that presented with GLE, 32 were taken to surgery and 11 were euthanized.

Seven of the 32 horses who were taken to surgery were euthanized on the table due to the need for resection and anastomosis that was declined by the owner.

In the EFE group, 58 of the 73 horses were taken to surgery, and 24 were euthanized on the table. Seven of the horses euthanized during surgery had severe intraabdominal hemorrhage from the portal vein, caudal vena cava

or ruptured mesenteric vessels.

“This emphasizes the importance of care when reducing these entrapments because of all of those anatomical structures that make up the boundaries of the foramen,” Dr. Kilcoyne explained.

Complications

There were no significant differences in the complication rates (56% for GLE and 62% for EFE) between the groups postoperatively, which included minor or major complications.

“We had a few horses with incisional complications,” Dr. Kilcoyne said. “One horse had a jugular vein thrombophlebitis, three horses had postoperative hemoabdomen, and one horse developed septic peritonitis. The most frequent complication was postoperative ileus. Six horses in each group had severe colic requiring relaparotomy.”

Overall survival to discharge was 88% in the GLE group and 85% in the EFE group. Factors associated with the pooled survival included peritoneal total protein and peritoneal lactate concentrations. Postoperative ileus was a significant complication that contributed to non-survival. Only 67% of horses with postoperative ileus survived compared with 100% of those without the complication.

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lameness

How accurate is your

arthrocentesis technique?

B y

P a u l

B a s i l i o

Shutterstock/Abramova Kseniya

The variable clinical signs and degrees of lameness associated with the distal hock joints can be challenging to diagnose. Radiographic guidance to confirm needle placement helps, according to a recent study.

When the focus turns to localization to determine whether the hock is indeed the cause of lameness, there are several options, according to Kathryn A. Seabaugh, DVM, DACVS (Large Animal), DACVSMR, of the University of Georgia.

“Radiography has been found to have poor correlation with disease unless there are severe osteoarthritic changes,” she said here at the 61st Annual AAEP Convention in Las Vegas. “Advanced imaging has given us a wealth of knowledge, but unfortunately we have to localize to the region before we can pursue imaging of the area.”

Intra-articular administration of anesthesia is still the gold standard for these types of patients, but the success of the procedure depends on the accuracy of the injection, she said.

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The Good News

The researchers were pleased with the accuracy of the TMT joint injections. Successful injections were noted in 23 of 24 joints (96%).

“The injection success matched our confidence,” Dr. Seabaugh said. “All of the successful injections were in joints where the veterinarians said they felt confident.

For the one missed injection, the veterinarian said that he was not confident in his injection.”

Communication between the TMT and DIT was present in only six of 23 successful joints (26%), and the average number of re-

sticks was less than one with a range of none to three.

“This indicates that the majority of veterinarians placed the needle once and that was it,” she explained. “Some re-sticks were due to horses moving.”

The Not-So-Good News

They were significantly less successful with the DIT. The veterinarians were accurate in 10 of 24 joints (42%).

“The confidence and injection accuracy were also significantly less than that of the TMT joint,” Dr. Seabaugh said. “Only 11 of 24 joints were confidently injected, and only six of these 11 confident injections were actually successful.”

Most of the missed DIT joints were missed proximally or even a little plantarly. The average number of re-sticks was again fewer than one, and most of these were necessary because the horse moved. The average number of repositions was about six, which was significantly greater than the TMT joint.

Extra-articular contrast media was noted in seven of 10 successful joint injections, and multiple attempts to inject had been made in three of those joints.

What It Means

The most important take-away from this study is the accuracy, Dr. Seabaugh said. The TMT has consistent landmarks, which leads to a high level of accuracy. The DIT joint has inconsistent landmarks, which can drag the accuracy down.

“In our survey of the operators after completion of the study, we found that many of them had developed their own techniques over the years, and many of them did

Images courtesy of Dr. Kathryn A. Seabaugh

Dr. Seabaugh and her colleagues set out to determine the accuracy of arthrocentesis of the distal intertarsal (DIT) and tarsometatarsal (TMT) joints across a small group of equine veterinarians. Six veterinarians were recruited to inject eight joints—four DIT and four TMT. Four of the veterinarians were equine surgeons, and two were surgery residents. The study participants were asked to use an injection technique described in Adams and Stashak’s Lameness of Horses.

“We hypothesized that the injection accuracy for the TMT would be 100%, but that the accuracy for the DIT would be less,” she explained.

After the injections were completed in both joints, the needles were left in place, and dorsoplantar and lateral medial views were taken. All radiographs were viewed by a board-certified radiologist who recorded the communication of the contrast medium and the location of the injection site. The veterinarians were then interviewed to discuss their confidence level with the injections.

not stick to the description of the injection in Adams and Stashak’s,” she noted. “One operator described using the width of his thumb caudal to the saphenous, and then just dorsal to the cunean tendon, and then he walked the needle in from there. That type of technique makes it hard to repeat across operators.”

Another consideration that should be made is to whether the repositioning or re-sticking of the needle could be causing joint capsule fenestration that leads to extravasion of the contrast medium. If there is extravasion or backflow of anesthetic in the TMT joint, then there is the potential for anesthetization of the lateral plantar nerve, which can confounding the blocking pattern. MeV

Here is an example of a missed distal inter tarsal injection. The star shows where they were aiming, and the line represents the misplaced needle.

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lameness

Oh, Those Aging Tendons The IFM is a soft, extendible material that allows the subunits to slide past one another, enabling the whole tendon to stretch.

Scientists at Queen Mary University of London (QMUL) are one step closer to preventing the kind of injuries that affect aging race horses like champion hurdler Rock on Ruby, the winner of Coral Hurdle at Ascot in 2015.

The team at QMUL's School of Engineering and Materials Science showed how the types of proteins differ in parts of the tendon, and importantly how this changes as the tendon ages.

“When a horse runs, its muscles generate a massive amount of energy that is stored and released by the tendons in its legs. These can be likened to massive elastic bands that absorb energy as they are stretched, and release it again when they recoil,” said Dr. Chavaunne Thorpe, post doctoral research assistant at QMUL. “The key to the effectiveness of tendons is the ability of the fibers that they are made up of to slide across each other. When this ability to slide is re-



Click here to see the video

duced, the energy damages the tendon instead of being stored and released by it.

“In this new study, we have identified specific proteins that help the tendon fibers to slide, and this research shows that these proteins are replaced less quickly as aging occurs. This makes injuries of the type that ended Rock on Ruby's career more likely.”

Rock on Ruby, the 2012 Cheltenham Champion Hurdle winner, famously went on to win the Coral Hurdle at Ascot last year despite suffering a career-ending tendon injury during the race, which resulted in the untimely retirement of the champion hurdler.

All tendons are made of subunits containing rope-like collagen surrounded by a material called the interfascicular matrix (IFM), which binds them together. The IFM is a soft, extendible material that allows the subunits to slide past one another, enabling the whole tendon to stretch.

The researchers identified which proteins are present and how rapidly many of the proteins in the IFM are refreshed in young tendons.

As tendons become older, the IFM becomes stiffer making it harder for the subunits to slide past each other. The results of this study indicate that the rate of proteins renewal drops with aging in the IFM specifically.

“Our research proves that the increase in tendon injuries as horses age may be directly related to the slowdown in the renewal of specific proteins within their tendon tissues,” said co-author Hazel Screen, PhD, a professor at QMUL. Tendon injury is common in horses as well as humans, with an economic impact of more than $4.104 a year in horse racing. Around 16,000 horses are in training each year, and the tendon injury rate is as high as 43% with few horses returning to racing after injury.

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For more information: Thorpe CT, Peffers MJ, Simpson D, et al. Anatomical heterogeneity of tendon: Fascicular and interfascicular tendon compartments have distinct proteomic composition. Scientific Reports. 2016;6:20455 DOI: 10.1038/srep20455. http://www.nature.com/articles/srep20455 10

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technician update

By Brandi Larsen, CVT A 12-year-old Friesian gelding that was experiencing intermittent, yet chronic abdominal discomfort and a decreased appetite over the past month presented to the clinic. His long black mane and tail were full of shine and his coat was smooth and rich, not the typical presentation of a patient experiencing colic symptoms.

The clinician asked about his vaccination and deworming history, diet, daily routine and if there had been any environmental changes that may have triggered his symptoms. The owners stated that with IV flunixin meglumine given, his symptoms would improve for several days. With the episodes of discomfort becoming more frequent, the patient’s re-

ferring veterinarian recommended a second opinion to find the source of his mystery pain.

He was bright, alert and curious as to why he was at the practice, yet felt well enough to be on the unsuccessful hunt for a stray treat or two. His examination gave no hints as to the primary cause of his symptoms. His rectal temperature, heart rate and respiratory rate were 99.6° F, 36 beats per minute (bpm) and 16 breaths per minute, respectively. His heart was auscultated and found to have a normal sinus rhythm without evidence of murmurs or arrhythmias. Auscultation of his lungs was also within normal limits with no crackles or rales appreciated.

Following abdominal auscultation, it was determined that borborygmi was decreased in all four quadrants of the abdomen bilaterally, giving the clinician his first clue in the case. His mucous membranes were pink and moist. The patient’s capillary refill time was less than 2 seconds proving also to be

Images courtesy of Ms. Larsen

Exploratory laparotomy and enterotomy for the removal of an enterolith

Surgery to remove the enterolith

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technician update

The 12-year-old Friesian was bright, alert and curious with a long black, shiny mane and tail. His coat was smooth and rich—not a usual colic.

within normal limits. No heat, swelling or edema was palpated in the distal limbs and the patient’s digital pulses were normal. The results obtained from the primary physical examination did not give the clinician enough information for a diagnosis.

The patient appeared calm and relaxed. Transrectal palpation revealed small, firm fecal balls with a mild amount of mucous and digested blood observed, and he had a body condition score of 5 out of 9. No ectoparasites, wounds, abrasions or significant lameness were appreciated. No evidence of neurologic disease, weakness, or ataxia was observed, and the patient was not actively displaying signs of abdominal discomfort at this time.

A veterinary technician obtained a venous blood sample to test for Chagas disease, a complete blood count (CBC), chemistry 12 panel, fibrinogen, packed cell volume (PCV) and total protein analysis. While waiting for the lab results, the patient again was convinced that he has been such a great patient that he deserved a treat. Unfortunately, without answers, he would have to settle for a neck scratch and kisses from his owners.

Still everything within normal limits

His CBC was unremarkable and revealed a normal PCV of 32% and total protein result of 7.4 mg/ dL. His white blood cell (WBC) count was 6.0 K/ uL (neutrophils accounting for 69.7%) and the red blood cell (RBC) count was 6.48 M/uL. His chemistry profile was also within normal limits. The clinician obtained a fecal sample to submit for an egg count and a free catch urine sample for a complete urinalysis, culture and sensitivity. The fecal egg count result showed the patient as a low shedder at 50 eggs/g of feces and the urinalysis had no abnormal findings with a specific gravity of 1.036 and no growth was observed following the urine culture and sensitivity analysis. The Chagas disease serum test results were also negative.

After discussing the findings of all preliminary diagnostics with the owners, it was decided to perform a gastroscopy to examine the esophagus and stomach. The patient’s stomach was completely 12

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empty allowing visualization.

The gastroscopy revealed no evidence of past or active equine gastric ulcer syndrome and the Margo Plicatus was observed to be within normal limits with no signs of squamous ulceration, inflammation or masses. The pylorus and cardia were also within normal limits with no signs of glandular ulceration. While removing the gastroscope, the esophagus was mildly distended with air and minimal bile was observed in the distal one-third of the esophagus. The clinician administered a prophylactic dose of omeprazole orally.

The clinician moved on to a more in-depth examination by performing a thoracic and abdominal ultrasound. His thorax was unremarkable with no comet tails, consolidation, or abscessation appreciated while his abdomen revealed normal renal, splenic and liver architecture, with a normally sized stomach. The left colon was observed to be gas distended while the right colon was found to be mildly edematous. The patient’s small intestine in the ventral flank area was mildly thickened at 5.9 mm and no peritoneal fluid, masses or abscesses were noted along the visible wall. He was hospitalized under constant observation for even the slightest change in mentation or physical status.

To keep the patient hydrated and stable, he was given maintenance IV fluid via a jugular IV catheter. The clinician started the patient on IV crystalloid fluids (Lactated Ringer’s Solution) with calcium gluconate 23%, vitamin B complex, vitamin C and potassium chloride. He was also offered 2 lbs of Purina Equine Senior Feed as a mash and started on IV antibiotics every 24 hours. When he was all settled in, the waiting game began.

At approximately 11:48 pm, the overnight veterinary staff noticed that the patient became alert, responsive and appeared nervous, which they had not observed before. He began to walk in a circle around his stall and positioned himself comfortably in sternal recumbency for about 30 minutes with no attempt to roll, thrash or even appear to be in distress. The staff continued to monitor him for any change and evaluated his heart rate once he stood up. His heart rate was determined to be within rela-

tively normal limits at 48 bpm. His IV catheter was flushed with heparinized saline and determined to be patent while IV fluids were continued. Since hospitalization, defecation had not been observed, however, he was displaying a moderate amount of flatulence but still no solid indications of abdominal discomfort.

The primary clinician returned in the morning following the uneventful evening hoping for news.

He performed a physical examination, which to no surprise was deemed to be unremarkable with the exception of increased borborygmi in all four quadrants of the abdomen following auscultation. The clinician elected to obtain a blood sample for a subsequent CBC analysis. Frustratingly enough, the results were unremarkable aside from mild polycythemia possibly indicating GI disease of unknown origin.

The patient again began showing visible signs of abdominal discomfort around 7:00 am severe enough to warrant mild IV sedation. The staff sprang into action by performing an abdominal ultrasound during the episode in hopes of finding another piece of the puzzle, however the ultrasound revealed no new information. Fluid ingesta was appreciated in the colon with hypermotile small intestine. Transrectal palpation was then performed, and a small amount of soft feces was appreciated in the rectum. Mild gas and ingesta in the right colon led the clinician to believe the patient may be displacing his right colon. He was placed back on observation where he passed a small amount of soft feces and diarrhea.

Some discomfort

Afterward, the patient stood comfortably and quietly through most of the morning. A repeat abdominal ultrasound was performed again around 9:30 am and resulted in the finding of small, yet consistent colonic vessels indicative of a previous right dorsal colon displacement, finally. The patient was observed throughout the day with no signs of discomfort. He passed additional small amounts of diarrhea throughout the day but appeared relatively comfortable with all subsequent physical examinations within normal limits. IV fluids were continued with no change in rate without incident.

The following morning, day three of observation, at about 7:00 am, the patient was again, significantly uncomfortable and was displaying behavior associated with a moderate colic episode. He was pacing, restlessly lying down and standing up, as well as pawing and kicking at his abdomen. This was the most severe episode thus far, hopefully providing

some insight to further clues. A nasogastric tube was passed through the left nares and into the stomach, yet no gastric reflux was appreciated. His heart rate was within normal limits at deparate 44 bpm, which did not traditionally match up with the degree of discomfort observed.

All findings, results and observations up until this point were discussed with the owners who opted to continue monitoring the patient until he either continually improves or severely declines. Throughout day three, he displayed continued anorexia and his mentation became moderately dull, which was a new development. A physical examination was performed at 8:00 pm and the patient was found to be mildly febrile with a rectal temperature of 101° F. This was the first major physical change other than the discomfort.

New bloodwork showed a possible infection. With the previous examination findings possibly indicating GI disease, these new results were slowly piecing together the diagnostic puzzle. The clinician administered a dose of flunixin meglumine IV and every 12 hours thereafter, to combat the patient’s pyrexia.

While still a mystery, he was subsequently febrile again at approximately 8:00 pm with rectal temperature of 101.3° F but with an unremarkable heart rate of 42 bpm and respiratory rate of 12 breaths per min.

Febrile

By the following day, the patient was still mildly febrile during his 7:00 am physical examination with a rectal temperature of 101.2° F but again, the remainder of his examination was frustratingly unremarkable. The patient was referred to a facility with a radiologist and advanced ultrasonography equipment.

The radiology report stated that a large mass was appreciated in his GI tract that was indicative of a large enterolith symptomatically fitting the patient.

After careful discussion with both the owners and surgical staff, it was elected to attempt to combat the infectious disease process with antibiotics and IV fluid therapy until the patient was normothermic and stable enough to attempt to reduce anesthetic risk and patient morbidity associated with an upcoming and imminent exploratory laparotomy.

Over the next three days, tensions remained high knowing what the future would hold for this patient. IV fluids were continued with additives as well as the addition of IV cefazolin every 8 hours and IV polymyxin B every 12 hours. He was started on oral probiotic paste, as well as continued omeprazole paste every 24 hours to increase his appetite and calm his abdominal discomfort until he was deemed ModernEquineVet.com | Issue 6/2016

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technician update

stable enough for an exploratory laparotomy. Prolonging the start of surgery was a difficult decision to make, but the risks versus benefits had to be weighed

Weighing the benefits vs. risks

Prolonging the horse's surgery was a difficult decision to make, but the risk versus benefits had to be weighed.

The risks of waiting included unforeseen increase or decrease of his disease process systemically, further decline of the patient, GI rupture at an unknown location and endotoxemia. The benefits of waiting for surgical correction included less morbidity risk during general anesthesia and overall systemic patient stabilization for a general anesthesia with less risk and postoperative recovery.

His owners visited him frequently and the bond between them was evident. Unfortunately, his temperature continued to rise to 103.5° F the following day after the decision to withhold an attempt at surgical correction until the pyrexia had dissipated with no associated signs of discomfort. IV fluid, antibiotic and GI therapies were continued and luckily, he became normothermic the following morning.

Necropsy Results Although the clinician was confident that metabolic acidosis and respiratory distress played a major role in his death, a necropsy was performed post-mortem. Unfortunately, the primary cause of pyrexia and abdominal discomfort was the pre-existing enterolith in his GI tract, which can be a silent killer if left undiagnosed for too long. He was only clinically symptomatic for approximately 30 days prior to his diagnosis and unfortunately, that was not enough time for him to present and stay stable and healthy at the time of surgery. He became febrile, which also indicates a systemic disturbance assumably stemming from the enterolith. This large patient was adequately positioned and padded at the time of surgery to minimize postanesthetic complications. The duration of anesthesia was not abnormally increased, and he remained stable throughout the surgery.

Losing a patient is never easy, no matter what the circumstance.

Members of veterinary staff develop relationships with their patients, also bonding them to owners and trainers. It is easy to feel helpless following an unpredicted death, however, working as a team, having a plan in place for postanesthetic complications and attending continuing education meetings can ensure that things go smoothly during an emergency. Sadly, the mortality rate associated with equine anesthesia should always be considered, especially during an emergency.

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It is rare to see an exploratory laparotomy on the practice schedule instead of by emergency, however, the patient was scheduled for an exploratory laparotomy to remove the suspected enterolith from the GI tract.

The patient was prepared for surgery by being brushed of all debris, feet cleaned and his mouth was rinsed to avoid aspiration of debris. Due to his breed and size, a real concern was the increased risk of postoperative muscle myopathy or nerve paresis.

He was given a preanesthetic sedation combination of butorphanol and xylazine followed by a small bolus of guaifenesin IV. The patient was induced for general anesthesia with a combination of ketamine and midazolam IV without incident and was intubated with a size 26-mm endotracheal tube in sternal recumbency to avoid the risk of reflux. He was positioned on the operating table in dorsal recumbency on 14-inch thickness operating table padding.

Due to his already compromised state and his size, he became hypotensive with a mean arterial blood pressure (MAP) of 65 mm Hg immediately following induction at which time a dobutamine constant rate infusion (CRI) was administered IV to combat his hypotension, promote organ, tissue and muscle perfusion, as well as battle postoperative muscle myopathy. He responded well to the CRI, and his MAP increased to normal limits of between 80 and 90 mm Hg throughout the remainder of the procedure. The enterolith was removed successfully and was equivalent to the size of a cantaloupe which would cause obvious discomfort to any patient.

The patient’s general anesthesia was relatively uncomplicated and, uneventful, and the patient was moved into recovery and positioned in left lateral recumbency. No abnormalities were appreciated on any of the arterial blood gas results obtained throughout the exploratory laparotomy proving his metabolic and respiratory status was maintained within normal limits.

While being carefully monitored in recovery, he immediately began spontaneous respirations with no increase respiratory effort. Once the patient developed horizontal nystagmus, he was sedated with IV romifidine to allow him sufficient time to recover from the sevoflurane gas inhalant anesthesia. He re-

news notes

About the author

randi Larsen, CVT, is an independent B consultant in Weatherford, Texas. She has piloted and implemented custom veterinary training programs in large animal practices in Texas as well as lent her knowledge as a speaker at veterinary conferences nationwide.

The Irish Take Liver Fluke Survey Blood markers and the fecal coproantigen ELISA are not reliable tests for fluke infestation, according to a recent study in the Equine Veterinary Journal.

The recombinant CL1 ELISA has a high specificity but low sensitivity, and other methods of ante-mortem diagnosis warrant investigation, the researchers said.

The researchers determined the prevalence of Fasciola hepatica infestation in horses in Ireland, and evaluated an indirect ELISA as a diagnostic tool. Two hundred horses were selected randomly at an abattoir and were placed into four groups based on their ante-mortem health status at ante-mortem examination.

On gross post-mortem examination, liver samples were graded from 1 to 6 (1 being lack of visible pathology, through mild to moderate changes, and 6 observations of fluke in the liver. ) Periductular fibrosis, periductular cellular infiltrates and hyperplastic changes in A liver fluke the biliary epithelium were graded from 0 to 3 giving a maximum score of 9. Blood was collected for hematology, biochemistry and an indirect ELISA test based on F. hepatica recombinant cathepsin L1 antigen (CL1) and fecal egg counts (FEC) were performed.

The prevalence of liver fluke infestation was 9.5% (19 of 200 horses). Most of the positive horses had clinical grade 2 (lesions of no clinical significance) or 3 (evidence of underlying chronic disease), with only four showing non-specific signs of current clinical disease, highlighting that liver fluke infestation is often subclinical. In 16 of the 19 positive cases, adult fluke were seen in the liver. In fluke positive horses, the mean histological score was 6.5 (of a maximum 9), compared with in the fluke-negative horses.

There was no association between fluke status and total protein, albumin/globulin ratio and eosinophilia although these variables were associated strongly with strongyle infestation. There was also no association between fluke and any of the biochemical parameters (including GGT activity) and bile acid concentrations (an indicator of liver function) were within normal limits in all horses. Importantly, this suggests that hematology and blood biochemistry are not reliable for detecting potentially affected horses.

When the recombinant CL1 ELISA results were compared with the fluke status (based on post-mortem findings and FEC), the ELISA had low sensitivity (42.1%) but high specificity (95.6%), suggesting that the immune response to fluke infestation in horses may be different to other species in which similar ELISA tests are more sensitive.

Fluke eggs were observed on fecal sedimentation in six horses, four of which also had adult fluke on gross post-mortem. The fecal coproantigen ELISA was performed on samples from 42 horses and failed to detect infestation in any of them, including six that had adult fluke on gross post-mortem, showing this to be a very unreliable diagnostic tool. MeV

Images courtesy of The Equine Veterinary Journal

gained laryngeal function, swallowed and was extubated without incident.

About 30 minutes after extubation, the patient attempted to roll into sternal recumbency and stand but was repeatedly unsuccessful with increased respiratory effort and apparent weakness in his hind limbs. The attending surgeon, clinician and other members of the support staff calmly, carefully and quietly entered the recovery stall and upon a subsequent venous blood gas analysis determined the patient was experiencing severe metabolic acidosis with a pH of 6.8. The clinician began to administer sodium bicarbonate 8.4% in Lactated Ringer’s Solution (LRS) IV as a bolus to correct the metabolic acidosis while others staff members attempted to keep the patient calm and free from panic.

While still suffering from apparent distress, the patient was intubated nasotracheally and an intranasal cannula was passed into the nasotracheal tube. Once secured in place, 100% supplemental oxygen was administered to the patient. Even with the sodium bicarbonate 8.4% supplementation, the patient was still acidotic and displayed signs of respiratory distress.

He rolled into sternal recumbency and once stable enough to be manipulated, he was carefully positioned in a sling to assist him to a standing position. Head and tail ropes were used and as a smooth and calm attempt was made to assist the patient into standing with the help of the sling, he became agonal and was lowered into right lateral recumbency. Epinephrine was administered IV and a member of the support staff attempted to thump on his chest over his heart with her body weight behind her elbow to resuscitate the patient although usually unsuccessful.

Sadly and unfortunately the attempt to resuscitate our gentle giant was unsuccessful, and he passed away in the recovery stall two hours postoperatively. The entire staff was devastated for our patient and for his owners.

This beautiful and stoic gentle giant galloped his way into the hearts of everyone involved that day and will be remembered fondly.

MeV

For more information: Quigley A, Sekiya M, Egan S. Prevalence of liver fluke infection in Irish horses and assessment of a serological test for diagnosis of equine fasciolosis. Equine Vet J. 2016.

May 27. [Epub ahead of print]. http://onlinelibrary.wiley.com/doi/10.1111/evj.12577/abstract ModernEquineVet.com | Issue 6/2016

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oncology

Genetic Susceptibility Do Horses Have

A 3 cm sarcoid tumor on a horse’s ear. Sarcoids often develop as small bumps under the skin or scaly lesions like the one in the photo. Depending on their location on the horse’s body, tumors like these can often be removed by a veterinarian.

However, in certain horses sarcoids tend to regrow after surgery, sometimes to much larger tumors that are impossible to cure.

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Images courtesy of Univesity of Cornell

to Sarcoids?

Sarcoid skin tumors are the most common form of cancer in horses, but little is known about why the papillomavirus behind them strikes some horses and not others.

A new study by an international research group led by scientists at the Baker Institute for Animal Health at Cornell’s College of Veterinary Medicine in Ithaca, NY, shows that genetic differences in immune function among horses partly accounts for these differences. The study mirrors findings in humans, as some people have a genetic susceptibility to human papillomavirus, which can cause cervical and other cancers.

“Many therapies have been proposed as the ‘best’ treatment for sarcoids,” says Cornell's Doug Antczak, VMD, PhD, Dorothy Havemeyer McConville Professor of Equine Medicine, who led the study. In some horses, tumors develop as small bumps under the skin or as scaly lesions that easily can be removed by a veterinarian, but in others, the problem becomes much more serious. Surgery, cryotherapy, laser treatment, injecting the tumors with drugs to kill the cells, radiation treatment and immunotherapy have all been shown to cure these recalcitrant tumors, “but some tumors tend to recur no matter what treatment is used, and there is no universal consensus on a uniformly successful therapy,” said Dr. Antczak.

For years, researchers have thought that bovine papillomavirus (BPV) is the most likely culprit behind sarcoid tumors. Recent work from Europe suggests variants of the BPV have become adapted to horses and are probably the cause of most sarcoids, Dr. Antczak said.

Dr. Antczak and his team

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applied a genomewide association study to compare the genetic makeup of horses with and without sarcoid tumors at more than 50,000 sites in the equine genome.

They studied 82 sarcoid-bearing horses from the United States and United Kingdom and 272 carefully matched controls that did not have sarcoids. They found regions on chromosomes 20 and 22 that tended to be different in horses diagnosed with sarcoids, evidence that a horse’s genes determine, in part, how susceptible it is to sarcoids.

“This is an example of more complicated genetics – multigene susceptibility,” said Dr. Antczak.

“More than one genetic region is associated with susceptibility to sarcoids, and they don’t completely determine whether or not a horse will develop the disease once it’s exposed to BPV.” This genetic link implicates the

Images courtesy of Cornell University

oncology

Cornell’s Doug Antczak, DVM, and his collaborators found that the region of chromosome 20 associated with sarcoid development is within a portion of the genome responsible for immune function.

immune system in sarcoid susceptibility. The region of chromosome 20 associated with sarcoid development is within a portion of the genome responsible for immune

function called the major histocompatibility complex (MHC) class II region. The MHC type associated with sarcoid susceptibility is rare among Standardbred horses, a fact that may explain why sarcoid is diagnosed so rarely in this breed.

This complex mix of virus, host genes and tumor development may have relevance to a related human condition. Tumors caused by HPV account for more than 5% of cancer cases worldwide. In women with cervical cancer, an association with the MHC class II region has also been shown.

“That should make a light bulb go off,” Antczak said. “It suggests there’s a common mechanism in both species for susceptibility to tumor progression that may involve subversion of the host immune response. By studying this phenomenon in horses you can learn about human cancer and vice versa.” MeV

For more information: Staiger EA, Chia TT, Miller D, et al. Host genetic influence on papillomavirus-induced tumors in the horse. Int J Can. 2016 May 6 [Epub ahead of print]) http://onlinelibrary.wiley.com/doi/10.1002/ijc.30120/abstract

Auburn Gets New Standing CT for Large Animals

Images courtesy of Auburn University College of Veterinary Medicine

The Auburn University College of Veterinary Medicine added standing commuted tomography (CT). For radiology and equine faculty, this advanced diagnostic tool has already proven to make a significant difference in diagnosing and treating complicated diseases found in a horse’s neck and skull. Robert Cole, DVM, an assistant professor of radiology, said the concept behind standing CT was to allow cross sectional imaging of the horse’s head without anesthesia.

Typical CT requires anesthesia, which can be risky. The standing CT creates cross sectional images of the skull and upper part of the cervical spine. Dr. Cole said the machine is allowing surgeons to understand “exactly what is going on before the surgery takes place. Typically, on a lot of cases, a horse may present with a nasal discharge.

“We’d start with radiographs traditionally and we might see fluid in the sinus but we couldn't tell why it was there or the origin. The surgeon would go in and explore that sinus, not knowing exactly what they were getting into.” The standing CT, in the same amount of time or less time, can have that cross-sectional imaging and locate the boundary of the disease process and its location. “The surgeon now knows exactly how to plan and knows what they are up against.”

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news

The oral D-glucose test has a good degree of repeatability in ponies under controlled conditions, and a carbohydrate-based feed is a suitable alternative test substrate, according to a recent study in the Equine Veterinary Journal.

The oral glucose tolerance test is used commonly to detect insulin dysregulation. The standard protocol involves feeding 1g/kg bodyweight of D-glucose (dextrose) powder in bran and collecting postprandial blood samples for insulin. In a recent study, researchers from Queensland University in Brisbane, Australia, used 0.75g/kg D-glucose for greater palatability, mixed with a fixed amount of wheat bran and lucerne chaff.

Of 12 ponies originally sourced for the study, eight were finally included as they showed good acceptance of the glucose test diet.

First a repeatability study was undertaken: following overnight fasts, oral glucose tests were performed on two ponies at a time (to ensure consistent washout periods) on three separate occasions over a three-week period. Blood glucose and serum insulin concentrations were taken before the glucose meal, and at 90 and 180 minutes and 24 hours.

Blood glucose levels were also measured immediately after feeding.

They found that blood insulin and glucose concentration were higher than basal concentrations after the D-glucose feed in all ponies and had returned to baseline 24 hours. Overall, insulin concentrations did not alter significantly in individuals among the three tests, and there was no significant difference in insulin concentrations at different points after feeding. Glucose results showed a higher degree of variability than insulin concentrations, particularly in the post-prandial samples.

Overall the oral glucose test had a good degree of repeatability in most ponies. However there was a large degree of variability in one individual pony, indicating that the test may not be reliable in all individuals and results must be interpreted within the individual clinical context.

The study also demonstrated that blood sampling at around two hours post-feeding as per the current recommendations is suitable for achieving

Courtesy of The Equine Vet Journal

Oral glucose tests repeatable in ponies

As some ponies found the test diet unpalatable, an alternative test diet consisting of commercial cereal-based pellets was explored. diagnostic results.

As some ponies found the test diet unpalatable, an alternative test diet consisting of commercial cerealbased pellets was explored. Pellets containing 0.75g/kg bodyweight of non-soluble carbohydrate were mixed with wheat bran and lucerne chaff. Blood glucose and serum insulin concentrations with the pellets correlated well with those in the D-glucose diet and there was good agreement with improved compliance and better palatability MeV

For more information: de Laat MA, Sillence, MN. The repeatability of an oral glucose test in ponies. Equine Vet J. 2016. May 23. [Epub ahead of print]. http://onlinelibrary.wiley.com/doi/10.1111/evj.12579/abstract ModernEquineVet.com | Issue 6/2016

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