The Modern Equine Vet - January 2022

The Modern

Equine Vet www.modernequinevet.com

S. zooepidemicus: Flexible and Opportunistic Major Foot-Forward for Laminitis Technician Update: Managing a Strangles Outbreak Optimal Oxygenation During Laparotomy New Feature: Monthly ID Update

ASK THE INFECTIOUS DISEASE EXPERT

Vol 12 Issue 1 2022

TABLE OF CONTENTS

COVER STORY

4 Flexible and

Opportunistic Cover: Shutterstock/Abramova Kseniya

LAMINITIS

Major Foot Forward..................................................................................................8 TECHNICIAN UPDATE

Managing a Strangles Outbreak .....................................................................12 ORTHOPEDICS

Jaw-Dropping Recovery: 3D Printer Saves Dairy Calf ............................18 INFECTIOUS DISEASE

U.S. Infectious Disease Update: (Dec. 21 to Jan. 22) .............................20 NEWS NOTES

Optimal Approach for Oxygenating Horses During Abdominal Surgery...................17 Hagyard Offers Rotavirus B Testing..........................................................................................17 Cellular Receptors Identified for Eastern Equine Encephalitis......................................23 SPONSORED EDITORIAL

“Is Parasite Resistance a Concern with EPM Treatments?”........................................................3 ADVERTISERS Merck Sponsored Content .................................................................................3 Merck Animal Health..........................................................................................7 Arenus Animal Health/Assure Gold.................................................................9 American Regent/Adequan.............................................................................11

Arenus Animal Health/Releira........................................................................13 EpicurPharma.....................................................................................................15 Arenus Animal Health/Aleira..........................................................................19 Arenus Animal Health/Assure Gold...............................................................21

The Modern

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THE

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

“Is parasite resistance a concern with EPM treatments?”

T

his is a question I often get and find particularly puzzling. While the equine industry faces challenges with antimicrobial and anthelmintic resistance, concern about antiprotozoals inducing resistant parasites can likely be crossed off the list.

There are 2 primary reasons.

First, for resistance to develop, antiprotozoal drugs would need to be overused, selecting hardier organisms for survival. In my mind, that is not happening in the equine industry. Second, the life cycle of Sarcocystis neurona – the primary causative organism of EPM – shows us that even if resistance is selected, the parasite will die with the host. The rare exception would be if opossums scavenged the horse. Let’s take a closer look.

BIOLOGY OF S. NEURONA MAKES RESISTANCE HIGHLY IMPROBABLE

S. neurona sarcocysts typically are not found in the tissue of horses, and equine carcasses are rarely accessible to opossums.

Hence, a horse treated with an antiprotozoal drug is highly unlikely to harbor resistant forms of S. neurona that can then be ingested by opossums, completing the parasite’s life cycle. Furthermore, all drugs that are FDA-approved for the treatment of EPM have been shown to yield concentrations at steady state that are in excess of what is needed to inhibit S. neurona growth. There are likely strains of S. neurona that are less susceptible to antiprotozoals, but that does not make them resistant.

FIGURE 1: Life cycle of Sarcocystis neurona

The life cycle of S. neurona is the primary reason concerns with antiprotozoal resistance are unjustified. The parasite’s life cycle ends with the horse unless the opossum scavenges the horse, which is unlikely.

Sarcocystis neurona has a 2-host life cycle – a definitive host, the opossum, and several intermediate hosts, with skunks, raccoons, armadillos and cats among the most common.

Opossums are commonly infected with S. neurona and are a major source of infection for horses. The horse is a dead-end host and becomes infected with S. neurona by ingesting

food or water contaminated with opossum feces (see Figure 1). S. neurona cannot be transmitted horizontally among horses, nor can it be spread by nonequine intermediate hosts.

Although limited evidence exists that the horse may serve as a natural intermediate host for S. neurona1, it is unlikely that horses are normal intermediate hosts that contribute to the parasite’s life cycle. This is because

WHAT HAPPENS IN THE HORSE, STAYS AND DIES IN THE HORSE

Resistance is often a result of product overuse (or incorrect use), as we have seen with antibiotics and deworming compounds. However, the same comparison cannot be made with EPM treatments. Not only is overuse of EPM treatments unlikely, but the biology of the inciting parasite makes resistance highly improbable. In the words of the late President Harry S. Truman, [when it comes to S. neurona in the horse] “the buck stops here.”

1. T. Mullaney, et al. Evidence to support horses as natural intermediate hosts for Sarcocystis neurona. Vet Parasitol. 2005;133:27-36.

ABOUT THE AUTHOR 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 information, visit https://www. merck-animal-health-usa.com/species/equine/ products/protazil.

Copyright © 2022 Intervet Inc., d/b/a Merck Animal Health, a subsidiary of Merck & Co., Inc. ModernEquineVet.com | Issue 1/2022

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INFECTIOUS DISEASES

Flexible and

Opportunistic Dry Cough? Nasal Discharge? Keep S. zooepidemicus in the Differential for Respiratory Diseases

The organism, Streptococcus equi subspecies zooepidemicus is the bacterium that is most often recovered from a horse’s oropharynx even when healthy, which might suggest that it is not a serious threat, but Andrew Waller 3rd, PhD, the chief scientific officer at Intervacc in Sweden, thinks it is cause for concern.

Several recent studies show that S. zooepidemicus is quite the opportunist and can cause a variety of diseases in many animals, including humans. Often by the time there are clinical signs, the organism has already spread around the barn, according to Dr. Waller.

“The disease is often subclinical, so it can be quite tricky to pick up—sort of a bit like COVID—it can spread around without many signs, and then every now and then, you get a flare up of severe disease,” he explained.

You might consider including it in the differential in an animal with obvious cough, he said, and be vigilant about biosecurity and wearing personal protective equipment (PPE). Not only does it spread swiftly among a group of horses, but it can sometimes affect B y

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the people caring for them.

“It is something to watch out for,” he said at the American Association of Equine Practitioners Annual Convention 2021. “If you ever treat animals that are obviously coughing, just be aware that it can jump into humans. It's flexible and opportunistic, and it's got a variety of mechanisms to allow it to cause disease in different animal hosts.”

Human cases of S. zooepidemicus can be extremely serious, he added, mentioning one case in a caregiver in Iceland during an outbreak who suffered septicemia and a miscarriage, and tested positive for the particular strain of S. zooepidemicus that was causing the outbreak.

“It’s just something to bear in mind, if you go and see an animal that has obvious respiratory signs of disease, it might be worth wearing some sort of PPE,” he said.

“The risk of it transferring to humans is really small, but when it does, it can cause really nasty disease.”

Streptococci occur in many different animals, and they cause a variety of different diseases. Most veterinarians are familiar with S. equi, the cause of strangles, a com-

R o s e n t h a l ,

M S

tion period was around 2 weeks and the signs lasted 4 to 6 weeks, but largely depended on the dose of the pathogen that the horses received, he explained. “So, if they were densely packed together in barns, then they seemed to have a shorter incubation time and a longer duration of signs than if they were outside in the fresh air.”

The outbreak quickly spread to other regions of the country, and by May, cases were found in the East and south as well. That quick spread suggested “the incursion of a new viral agent,” he explained.

To determine the cause, 3 healthy horses were introduced to an infected stable and monitored carefully every day for respiratory signs. After about 19 days, the horses had a cough and mucus discharge. They were euthanized on day 21 or 28.

There was excess mucus in the respiratory tract. Samples were taken and sent to various laboratories around Europe for extensive investigation, looking not only for equine pathogens, but also pathogens of humans and other animals as well, but no viral agent was identified that was consistent with disease in these horses. They also looked for S. equi even though there was no lymph node abscesses. All the samples were negative on both

Shutterstock/Haim Rosenfeld

mon infectious disease in horses, often characterized by fever and abscesses of the lymph nodes. They might be less familiar with S. zooepidemicus, although it has been associated with respiratory diseases, uterine infections and ulcerative keratitis in horses.

He talked about an outbreak in Iceland that was particularly interesting because of how quickly it spread in this closed community. Icelandic horses are an extremely robust breed that can tolerate the country’s extreme weather conditions, so the country has taken great efforts to keep the breed robust—imports are banned. “Because of this lack of import, they're free from the most serious diseases in horses, such as equine influenza virus, equine herpesvirus 1, and of course, strangles, but that means that they're extremely vulnerable to these and other new agents that might be introduced into Iceland,” Dr. Waller explained.

In April 2010, a respiratory disease was identified in several horses in an equine center at Holar University in the northern part of Iceland. Most of the animals had a dry cough with a serous nasal discharge that became mucopurulent over time; laryngitis and mucus in the tracea were also signs. Most horses did not have a fever. The incuba-

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INFECTIOUS DISEASES

Shutterstock/Olhastock

EMERGING STRAINS New strains are constantly emerging and spreading, according to Dr. Andrew Waller.

Right now, they are tracking a variant (SD194) that was first identified in China and led to the death of hundreds of thousands of pigs in China.

It spread through Asia and was just recently identified and recovered from pigs that were dying of disease in North America, as well.

“And we've just recently had evidence that it can transfer to humans via consumption of raw pork products,” he said.

“One thing that we'd like to be able to do is to identify more disease-causing strains and use that information to understand how they're causing disease, so that we can minimize their effects and keep animals, whether it's horses or pigs or sheep or goats or so on, healthy in the future.

culture and polymerase chain reaction testing.

“So it wasn't, Streptococcus equi, however, almost all cases of animals that were ill with the respiratory signs had Streptococcus zooepidemicus recovered from them.”

They performed genome sequencing on 257 isolates from Iceland and found that 199 of these were clustered into 4 closely related groups that they called clade 1, 2, 3 and 4. They found clade 4 in 37 isolates from 8 horses clustered in one geographic area. They found clade 3 in 52 isolates from 14 horses and 1 dog at 8 farms. They found clade 2 in 28 isolates from 14 horses at 10 farms, and in 1 person.

They determined that none of them were the epidemic strain due to several factors, such as diversity and geography.

The researchers found their answer in clade 1, where they found 83 isolates from 45 horses at 21 farms, as well as 1cat and the woman discussed earlier. The isolates only differed by a maximum of 25 bases, so the researchers decided it had to be the epidemic strain.

“The amazing thing was that all these strains from all around Iceland—even though the geographical distribution was really high—only differed by 25 bases at the DNA level. They were incredibly closely related to one another. And so, this had to be the strain that was responsible for the disease that was being seen in Iceland at the time,” he explained.

They then did a trace-back and looked at the various affected premises and found 1 yard in the south of Iceland that used a submerged treadmill to train 6

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There was a report of a viral outbreak in more than 3,000 horses around New Market, U.K., but no virus was ever identified. “And unfortunately, no bacteria were recovered from these particular horses, either,” he said, “but the clinical signs—coughing and nasal discharge—were exactly what we saw in Iceland.

“So, it does make me wonder whether this could have been S. zooepidemicus.

“If you get cases like this, please get in touch because we've now got all of the tools that are required to be able to examine these in more depth and understand what might be causing the problem,” he said. Tools such as the Global Platform for Genomic Surveillance can identify outbreak strains and track transmission. So far, they have 670 isolates of S. equi from 19 countries.

“It's a really fantastic technique to understand what might be causing disease in particular groups of horses or other animals as well,” he said.

and rehabilitate horses.

“What we think happened is a horse that was underperforming had gone to this yard to be improved and trained, and it had shed S. zooepidemicus into the water. And then the subsequent horses that went through that treadmill during that day were being exposed to it,” he explained.

Since horses were typically only at the yard for a short period, the horses were returned to the original barn before they exhibited signs of respiratory disease.

“And then, of course, they were able to cough and spread it to all of the horses that were there, and we had the epidemic,” he said.

“Clearly this strain had just gone everywhere in Iceland, and there is no possibility of being able to eradicate it from the horse population.”

Three years later, they did a quick survey to see if the strain was still present, and they found S. zooepidemicus was a commensal agent. “And maybe that's because it's just present in the population, and we can't actually tease apart which strains are causing disease from the strains that are colonizing,” he said.

Their research suggests the strain was present in Iceland before the outbreak, but perhaps, that particular environment with the submerged treadmill enabled spread of a more virulent strain.

“Streptococcus zooepidemicus causes disease in a huge variety of animal hosts including humans, so it is something to watch out for,” he said, adding that it can spread without patient zero having any clinical signs.

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LAMINITIS

Dr. Samantha Brooks.

MAJOR FOOT FORWARD

Making Breakthroughs in Understanding Laminitis B y

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T o r y

M o o r e

(UF) and Pennsylvania (PennVet) made a major breakthrough in understanding laminitis. They looked at genetic information specific to hoof tissues to see what genes and proteins are involved in the process with the hope that there will 1 day be not only a noninvasive test for the disease, but treatments that target the inflammatory process itself.

“We have very few tools in our arsenal to manage the disease itself. We treat symptoms, pain and mechanical instability but do not have anything to target the cause just yet,” said Samantha Brooks, PhD, an associate professor of equine physiology at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS).

That’s because studies have been hindered by the scarcity of genetic information specific to hoof tissues. Scientists from the UF/IFAS and the University of Pennsylvania School of Veterinary Medicine tapped into PennVet’s New Bolton Center Laminitis Discovery Database, an archive of data and sample sets from naturally occurring laminitis cases collected since 2008.

They examined 36 archived tissues of 20 Thoroughbred horses treated for laminitis.

There are 3 types of laminitis, and all impair the structure and function of the horse’s foot. This research provided a snapshot of the active pathways and functions of the hoof, with a focus on supporting limb laminitis—the laminitis that lead to the death of the famous racehorse, Barbaro, in 2007.

“We understand the situations that trigger an episode of laminitis, but we do not have a good understanding of what is happening in the hoof,” said Dr. Brooks, who specializes in equine genetics. “This study took a very comprehensive view of the processes early in the development of laminitis.”

Using gene expression analysis, Dr. Brooks and her colleagues catalogued the changes in gene transcription in archived lamellar tissue from 20 Thoroughbred racehorses to identify trends in the disease process. They looked at tissue from horses with healthy hooves, horses with early disease and others with more severe disease.

“By tapping into my lab’s database and incorporating Dr. Brooks’ unparalleled expertise in equine genetics and transcriptome analysis, we have identified new and promising pathways in cell stress and inflammatory response that significantly enhance our understanding of supporting limb laminitis and its disease processes,” said Hannah Galantino-Homer, VMD, PhD, DACT, a senior investigator in laminitis research at New Bolton.

They found alterations in cell replication and growth, as well as gene expression and proteins that could serve

Image courtesy of UF/IFAS

A joint study between the Universities of Florida

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LAMINITIS

Red-green-bluelamellae: The "axial" end (away from the hoof, close to the coffin bone/distal phalanx bone) of a single primary fold or "lamella" (PEL) of the inner surface of a horse's hoof that has been stained using a blue DNA stain to identify the cell nuclei of the lamella and adjacent dermis, a red counterstain to help visualize the microanatomy of the lamellae, and a monoclonal antibody that identifies a keratin specific to the basal cells of the lamella (green).

Image courtesy of New Bolton Center

Laminitis research new bolton: The horse’s hoof lamellae consist of primary and secondary folds or "lamellae" (PELs and SELs) that increase the contact area between the hoof and underlying tissues, allowing the transfer of the horse’s weight from the bones of the limb to the hoof. In this confocal (laser technology) microscopic image, the basal cells of the SELs are stained green using an antibody against an epithelial basal cell keratin, K14.

as biomarkers for laminitis disease. In addition, nuclear receptor subfamily 1 group D member 1 (NR1D1) and other important inflammatory genes offer the promise of novel medical treatments.

“This is a big step in improving our understanding of laminitis,” Dr. Brooks said. “Something that could be completely untreatable 10 years ago; in another 10 years we may be able to intervene and make a significant difference in the disease early on.”

Scientists found a collection of genes responsible for triggering that inflammation that could pave the way for future medications to treat the inflammation. For instance, NR1D1 functions as a transcriptional repressor and has a role in rheumatoid arthritis; it was also seen in the laminitic tissues. The genes led researchers to think that some human medications for autoimmune disorders might help horses with laminitis.

Changes in gene expression in diseased tissue are often reflected in changes in the proteins that can be detected in the blood as the disease progresses. For example, increases in specific biomarkers, which can be seen in people following traumatic brain injury, were

expressed in the samples from the horses with laminitis in this study.

Medical doctors have used these compounds to understand the severity of these injuries in people without using imaging or more invasive testing. Dr. Brooks hopes this could be used as a tool to monitor the progression of laminitis in the horse and will lead to a blood test to detect laminitis-related biomarkers.

“We don’t always recognize that a horse has severe laminitis until things have gotten quite bad,” Dr. Brooks said. “Early monitoring tools and ways to combat the disease were exciting findings, but we need further research before these new tools will be ready for use in the field.”

Dr. Galantino-Hoomer added that the new findings will point “toward a more targeted approach for future exploration that we hope will help uncover novel solutions for preventing and treating this debilitating disease.”

MeV Funding for the study came from The Foundation for the Horse.

For more information: Holl HM, Armstrong C, Galantino-Homer H, et al. Transcriptome diversity and differential expression in support limb laminitis. Vet Immunol Immunopathol. 2022 Jan;243:110353. doi: 10.1016/j.vetimm.2021.110353.Epub 2021 Nov 9. https://www.sciencedirect.com/science/article/abs/pii/S0165242721001719?via%3Dihub Original article appeared on the UF/IFAS website; used with permission. It has been edited for style. https://blogs.ifas.ufl.edu/news/2021/12/01/breakthrough-laminitis-research-shows-promise-for-the-future/

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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.

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TECHNICIAN UPDATE

Managing a Strangles Outbreak

By Natalie McTaggart, AAS-RVT On May 2, 2021, the attending veterinarian was called out to a local boarding barn for a horse that had large amounts of nasal discharge, coughing and was not eating. Whiskey, a 13-year-old Quarterhorse mare presented with lethargy, exuberant amounts of nasal discharge that was thick and yellow, a deep cough and no appetite.

She had a fever of 103.6° F, a heart rate of 48 beats per minute (bpm) and a respiratory rate of 18 breaths per minutes (brpm). Her mucous membranes (MM) were pink, slightly tacky with a capillary refill time (CRT) of less than 2 seconds.

Her estimated weight was about 590 kg, and she had a body condition score 7 out of 9.

The boarding operation had an outbreak of Streptococcus equi, more commonly known as strangles, the prior year. Due to this history, the veterinarian obtained culture swabs to submit to the reference laboratory for an equine respiratory polymerase chain reaction (PCR) test, to determine what respiratory strain was present.

The mare was uncooperative, so the attending veterinarian administered IV xylazine, so nasal swabs could be collected. Since she was not showing any indication of wanting to eat and was very depressed from her normal attitude, along with her high fever, the veterinarian also decided to give IV flunixin meglumine at the dose of 1.1 mg/kg at 50 mgs/mL to address the fever and general discomfort. Ceftiofur crystalline free acid sterile suspension was given by intramuscular (IM) injection in the left side of the neck because oral antibiotics would be difficult to administer due to the lack of appetite.

The mare’s owner was informed that she would need another injection of antibiotics in 96 hours if the horse’s appetite and nasal discharge had not improved substantially.

Isolation of the infected mare was strongly suggested to the barn owner, but due to the layout of the paddocks with shared fence lines, every horse was already potentially exposed. Necessary precautions to help prevent the spread of the disease to the other 39 horses on property, including a broodmare that was due to foal in less than 30 days were discussed.

Suggested precautions to decrease the chance of accidental spread of the contagion included: • isolating the infected horse, • s topping all movement of horses around the property, 12

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• disinfecting of all community items of the barn, and • handling of the symptomatic horse(s) last.

After the attending veterinarian had given all recommendations, biosecurity protocols were discussed and implemented by the facility.

Along with working for the attending veterinarian, the registered veterinary technician was 1 of the main caregivers at this location and helped with all healthcare aspects at the facility. The infected mare was kept quarantined to her pen, with water and food intake closely monitored for improvements or declines.

Due to the mare’s uncooperative nature, daily collection of vitals was not obtained for safety of the staff. All feed scoops, buckets and gate latches were sprayed with a 10% bleach solution after every feeding and left at her pen. Shoes were also sprayed with the 10% bleach solution before caregivers returned to their housing to change clothes and shoes. Nothing worn at the barn was worn to the veterinary clinic and vice versa.

Whiskey was handled last at each feeding and contact was kept to necessary handling only. The other horses that normally were turned out with her were kept in their stalls to monitor for symptoms and to prevent any further exposure.

To limit the spread of the respiratory disease, all boarders were informed that a sick horse was being treated for a potentially contagious disease and that measures were being taken to limit the spread. Spray bottles with a 10% bleach solution were placed at all entrances to the barns, and owners were strongly encouraged to disinfect their shoes before entering and leaving. The facility owner encouraged owners not to visit their horse(s) at this time to help with controlling the spread of the disease. Outside horses coming in to use the facilities was prohibited until culture results were finalized and quarantine times could be established.

On May 6, ceftiofur crystalline free acid was administered again to Whiskey since her nasal discharge persisted, and the cough showed no improvement. Her appetite slowly returned, and her attitude continued to improve. Daily vitals were still difficult to obtain, so objective observations were used to judge progression and/or declines in her health.

Isolation and biosecurity protocols at this time were fully implemented and all boarders were being trained by oral communication to disinfect the

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TECHNICIAN UPDATE

Shutterstock/nelelena

Teaching Points Although this outbreak could have been significantly worse, constant communication and client education about infectious disease spread and proper disinfecting of communal items and areas played a substantial part in containing the disease from infecting any other horses, including the broodmare.

To limit the spread of the respiratory disease, all boarder owners were informed that a sick horse was being treated for a potentially contagious disease and that biosecurity measures were implemented.

Owners were encouraged not to visit their horse(s) at this time and outside horses coming in to use the facilities was postponed.

Owner education was critical, and included, but was not limited to, how the bacterial disease is spread, recurrent infections, preemptive measures to halt spread of diseases, and habits that help prevent any new disease outbreak at the barn.

bottom of shoes before entering and leaving the barn, heading out to turn-out paddocks and to spray stall latches and crossties after handling. Many of the boarders had adopted the protocol of changing shoes before heading out to the pastured horses and changing back into the “clean” shoes before entering the barn.

The 3 horses slotted to start showing in June and July were kept isolated as much as possible in the off chance that the quarantine would be lifted in time, and normal activities could resume.

The respiratory PCR results were available, and the mare had tested positive for both S. equi subspecies equi and S. equi subspecies zooepidemicus while the culture only isolated S. equi. Both the mare’s owner and the barn owner were informed of the results, and the boarding operation immediately went into a full quarantine that was not to be lifted until 14 days past the resolution of clinical signs. The area had experienced major rains and all turnout was halted and stalled horses were kept in their stalls until it could be determined that no other horse(s) were starting to show clinical signs of either bacterial disease. While many of the current horses being boarded there had contracted S. equi the previous year, Whiskey had 14

Issue 1/2022 | ModernEquineVet.com

not. There were also 11 additional horses that had moved onto the property following the outbreak the prior year; those horses were closely monitored twice daily for any change in behavior or signs of respiratory illness.

On May 13, 2 more horses presented with similar symptoms. Dubs, a 3-year-old Quarterhorse mare, approximately 550 kgs with a body condition score of 5 out of 9, presented with a deep cough, nasal discharge, inappetence and severe depression. The same attending veterinarian of the original case was called in to evaluate the mare and start treatments. Physical findings were a fever of 104° F, respiratory rate of 28 brpm, heart rate of 50 bpm, MM were pink and slightly tacky with a CRT of 3 seconds.

The owner agreed to a respiratory culture as this mare was a performance horse and had several upcoming shows to attend. The technician administered IV flunixin at a dose of 1.1 mgs/kg with a concentration of 50 mg/mL and ceftiofur crystalline free acid at a dose of 6.6 mg/kg concentrated at 200 mg/ mL. The mare was fully isolated in her stall, the barn stopped all turn-out again, and a halt movement was issued for all horses on the property.

The other horse to show symptoms was a 21-yearold paint mare, and her veterinarian was called to evaluate her. Owners of boarding horses were informed of the new cases and advised to continue limiting visitation and to not remove horses from stalls or paddocks in a continuous attempt to severely curtail the spread of the disease.

The pregnant broodmare was moved immediately from her paddock that shared fence lines with other horses to a stall in the lower barn that had no horses in it. Boarders were informed that she was in isolation and the barn was off limits to all but the facility owner and staff to control any contamination of her area.

Biosecurity measures were increased to include a foot bath with 10% bleach solution that was placed just inside the entrance to the lower barn, no wheeled vehicles or carts were allowed into the barn from other locations around the farm, and the broodmare was the first to be fed and the stall cleaned at the start of each round of chores.

Only the technician was allowed access to the mare and the handling of all horses at chore time to control contamination. While striving to hold the biosecurity measures to a high standard of excellence in accordance with clinical standards, constant reevaluation of disease management and equine health practices continued.

On May 14, Dubs vitals were taken after morning rounds had been completed. Her fever had dropped to

101.8° F, heart rate of 42 bpm, respiratory rate was 13 brpm with some effort, MM were pink and moist, and CRT of less than 2 seconds. She still was not interested in food, and • Isolating the infected horse a warm mash was made to try and coax her to eat. That evening her fe• S topping all movement of ver spiked to 105.8° F and she was horses around the property given another dose of IV flunixin.

• D isinfecting all community Her respiratory effort had increased items of the barn to 20 brpm and her cough continued to progress. As daily tempera• D isinfecting shoes tures were taken, she continued to • H andling the symptomatic have a persistent fever ranging from horse(s) last.

103.4° F to 106.1° F, and per the veterinarian, 10 mLs of flunixin was administered IV every 24 hours for the next 7 days to control the fever and inflammation of her submandibular lymph nodes. to be soaked into a mash consistency to make it easier She was placed on omeprazole oral paste at a dose for her to eat and electrolytes were added to her water. of 4 mgs/kg every 24 hours to help with the prevenOn May 19, flunixin was discontinued as Dubs was tion of gastric ulcer development from long-term use no longer showing drastic rises in her temperature, of nonsteroidal anti-inflammatories. Grain continued and her appetite was ravenous. A cough persisted,

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although no nasal discharge was present. Respiratory culture results came back as only S. equi, and no other bacterial strains were isolated, thus giving insight to controlling the outbreak further.

On May 24, all the horses that had symptoms of strangles were no longer symptomatic, and per the veterinarian, a 14-day waiting period had started. If no other symptoms were observed, the quarantine would be lifted, and normal activities could resume at the barn. However, all horses were closely monitored for resumption of symptoms and any new cases.

Protocols remained in place to continue containment of any residual contamination.

Not Out of the Woods

Warming temperatures, increased barn activity and residual contamination might have caused the outbreak.

Seven days later, on May 31, the fourth horse to show symptoms was noted. An 18-year-old paint gelding was slow to approach the feed bunk and was coughing to the point of hindering walking. The horse was isolated and monitored for signs of declining health along with the facility staying in full quarantine. The owner could not be reached, and therefore, no treatment was authorized. On June 13, all horses were deemed to be symptom free and the 14-day waiting period was started over.

No further horses developed symptoms, and the quarantine was lifted on June 27. Owners were encouraged to have their horse’s titers checked and to vaccinate if low to prevent a recurrent outbreak.

While some restrictions were lifted among the boarders, continuation of a modified biosecurity protocol was left in place. Spray bottles were left in strategic places and owners encouraged to continue spraying down communal items within the barn after use.

Throughout the outbreak, several other barns in the area announced similar problems. While it remains unclear where the outbreak started, it is theorized that with the warming temperatures and increase activity of the barn, residual contamination from the previous year was allowed to expose and, therefore, infect horses that did not have sufficient titers.

During the post-outbreak phase, several horses were slotted to start showing, and the owners were given a brief educational talk in proper show health protocols to limit any potential exposure to other diseases while at the shows. A review of the current barn’s health management plan, along with titer test, vaccinating as needed, and an increase in horse owner education, the chances of another recurrent outbreak should be diminished in the following years.

MeV

About the Author

Natalie grew up with an innate passion for animals, and frequently participated in livestock and horse shows as a member of the 4-H club. She received a degree in veterinary technology from Colby Community College, in Kansas, and launched her veterinary career at a mixed-animal practice in Hutchinson, then became the Animal Hospital Manager at a feedlot operation. Next, Natalie moved to Wichita and worked in small-animal medicine for 7 years before joining the Hodes Veterinary Health Center team in 2012.

Equine care is a particular passion of Natalie’s, and she loves the way that every case is unique. Equine sport medicine is a favorite, and she is currently working toward her kinesiology taping masterclass certification.

Natalie’s love of horses extends outside of her job—she competes in western dressage her Quarterhorse, Faded Hotrodder. The pair received Reserve World Champion at AQHA World in 2021 in Level 1 Western Dressage Amateur. At home, she and her fiancé have 3 horses, including a 6-year-old Thoroughbred racehorse, and their 2 dogs.

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Issue 1/2022 | ModernEquineVet.com

NEW NOTES

An Optimal Approach for Oxygenating Horses During Abdominal Surgery

By Adam Marcus A combination of drugs and mechanical ventilation appears to be the optimal approach for managing oxygenation in horses undergoing certain abdominal surgeries, new research showed.

Veterinary anesthetists in Belgium found that use of continuous positive airway pressure (CPAP) or inhaled salbutamol—a short-acting β2 adrenergic receptor agonist that relaxes the muscles in the airway and improves oxygenation—led to significant increases in lung function during laparotomy. The researchers reported their findings in a recent issue of Veterinary Anesthesia & Analgesia.

For the study, Charlotte Sandersen, of the Department of Clinical Sciences, Anesthesiology and Equine Surgery at the University of Liège, and her colleagues assessed the 2 approaches in 62 horses undergoing laparotomy with general anesthesia using midazolam, ketamine and isoflurane. Twenty-eight horses received salbutamol as the first intervention,

which was considered effective in 22 animals. The CPAP maneuver, at 50 cmH2O for 45 seconds, was tried first in 34 animals, and was effective in 26, according to Sandersen’s group.

Among the 6 horses for which salbutamol was ineffective, subsequent use of CPAP succeeded in 4 cases; whereas salbutamol was effective in 1 of the 8 horses for which initial CPAP failed.

Both approaches led to significant increases in dynamic compliance (Cdyn), a measure of the ability of the lungs to take in oxygen. However, only salbutamol was associated with a reduction in F-shunt, which inhibits proper oxygenation of blood, the researchers reported.

Salbutamol and CPAP-M were comparably effective in improving oxygenation and Cdyn in anaesthetized horses with PaO2 <100 mmHg (13.3 kPa).

Whether combining both treatments might be beneficial needs to be confirmed on a larger number of horses, they added.

MeV

For more information: Dupont J, Gougnard A, Salciccia A, et al. Comparison of single-breath continuous positive airway pressure manoeuvre with inhaled salbutamol to improve oxygenation in horses anaesthetized for laparotomy. Vet Anesthes Anal. 2021 Oct. 20; DOI:https://doi.org/10.1016/j.vaa.2021.06.018 https://www.vaajournal.org/article/S1467-2987(21)00291-9/fulltext#%20

Hagyard Offers Rotavirus B Testing Hagyard Equine Medical Institute now offers polymerase chain reaction (PCR) testing for rotavirus B as a single test or as part of Hagyard’s Neonatal Panel or Foal Diarrhea Panel.

Rotavirus B was a novel strain discovered in central Kentucky during the 2021 foaling season and was responsible for a wave of neonatal foals that presented with severe diarrhea between 1 and 4 days of age. Some farms even felt the effects of a 100% morbidity rate.

“This new strain caused considerable concern for our industry in the 2021 foaling season. To be able to offer testing moving into the 2022 foaling season is a great relief for our clients,” said Nathan Slovis, DVM, DACVIM, CHT of Hagyard Equine Medical Institute, a world leader in equine infectious disease response.

“We felt it was important that veterinarians both within and outside of the Hagyard practice have access to a lab like ours,” added Luke Fallon, DVM,

who is the medical director of Hagyard Equine Medical Institute.

As with all rotaviruses, biosecurity precautionary measures should be taken to reduce the risk of infection to other horses. Bleach is ineffective against rotavirus, so products such as Tek-Trol, Biophene, Environ, Accelerated Hydrogen Peroxide (Rescue) and Stroke-1 are examples of disinfectants that can be used.

Research is being conducted to better understand the virus and to develop a vaccine for young, susceptible horses. Current vaccines for rotavirus A do not protect against the new B strain. To that end, Hagyard’s testing and Laboratory can differentiate rotavirus B from rotavirus A strains.

MeV Find more information: https://www.hagyard.com/ services-and-facilities/hagyard-laboratory ModernEquineVet.com | Issue 1/2022

17

ORTHOPEDICS

Jaw-Dropping Recovery: 3D Printer Saves Dairy Calf

Image courtesy of Jesse Jones/University of Florida

By Sarah Carey 3D printing technology enabled a newborn calf with a broken lower jaw to fully recover.

“We were at the farm soon after she was born, and the staff asked us to look at her because she was standing with her mouth hanging open,” said Fiona Maunsell, BVSc, PhD, a clinical assistant professor with the UF College of Veterinary Medicine’s food animal reproduction and medicine service. Veterinarians from the service regularly visit the farm, run by UF’s Institute of Food and Agricultural Sciences and located in Hague, Fla., to provide care for its dairy cows and calves.

Trying to first stand after birth she nose-dived forward, hitting the ground right on the end of her chin, Dr. Maunsell said. Although the farm staff initially thought the injury was minor, when the UF team examined the calf more closely, they found she had a broken lower jaw.

Thousands of calves take their first steps every day, and almost all of them fall multiple times, but this was a first for Dr. Maunsell.

“This is the first time I’ve ever had a calf do this,” she said. “She was very feisty, though, running around her pen. And if you helped hold her mouth closed, she was able to nurse fine from a bottle.”

Although veterinarians can often repair breaks in the lower jaw in the field when they are at the front of the jaw,

Planning Potato’s cast.

adjacent to or between the front teeth, this calf’s break appeared to be on both sides at the back of the jaw.

“That’s not something we could repair with field anesthesia and surgery,” Dr. Maunsell said. The calf arrived at UF’s Large Animal Hospital as an emergency case on Jan. 7. When radiographs did not shed much light on her injury, the surgical team recommended a computed tomography (CT) scan, which showed the bilateral breaks.

“The options for treating a calf with this type of fracture are orthopedic surgery, which was not economically feasible, conservative management with stabilization of the jaw, or euthanasia,” Dr. Maunsell said. “Given that she has had such a great attitude, we thought we’d try conservative management.”

Working with Hongjia He, a graduate student in the Surgical Translation and 3D Printing Research Laboratory run by Adam Biedrzycki, DVM, an assistant professor of large animal surgery, and large animal surgery resident Heather Roe, DVM, sat down and built a jaw “cast” the printed on the 3D printer for the calf, which the veterinary technicians had named “Potato.”

Dr. Roe knew Potato would grow rapidly, so she assumed that they could adjust the initial 3D model to make it larger as she grew out of each cast, which is what the team wound up doing.

“The 3D print is made of a hard plastic, so we cushioned the print with cotton,” she said, adding that the final product came about through trial and error.

“The goal was to have something that stabilized her jaw so that the bone ends could heal together, allowed the calf to drink milk and was also taken on and off to clean as needed,” Roe said. “She was very wiggly, so having a cast that was easily applicable was important.”

After a few days, the calf was sent home, and follow-up imaging at 1- and 2-month intervals revealed that Potato’s fractures were healing well.

A second CT at the 2-month recheck showed that the fracture lines were almost fully healed and her jaw was stable on palpation, so the cast was removed.

“Because her ordeal in early life meant a delay in moving from milk to solid food, she is about a month behind her herd mates in development, but we now fully expect her to go on to become a valued—and much loved—member of the adult herd,” Dr. Maunsell said.

MeV

The article originally appeared on the University of Florida, College of Veterinary Medicine website: https:// www.vetmed.ufl.edu/2021/12/20/jaw-dropping-recovery-uf-veterinarians-save-injured-dairy-calf-usingcreative-3d-solution/. It was edited for style and used with permission.

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Issue 1/2022 | ModernEquineVet.com

IN A WORLD OF ITS OWN

Researched Respiratory Support Researched and Proven as an aid in controlling IAD and RAO Recommended in the ACVIM Consensus Statement on Respiratory Disease (1)

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– Using the Best Matters References: [1] Nogradi N, Couetil LL, Messick J, Stochelski MA, Burgess JA. Evaluation of an Omega-3 Fatty Acid Containing Feed Supplement in the Management of Horses with Chronic Lower Airway Inflammatory Diseases. J Vet Intern Med 2015; 29:299-306.

[2] Couetil LL, Cardwell J.M, Gerber V, Lavoie J.-P, Leguillette R, Richard E.A. Inflammatory Airway Disease of Horses. ACVIM Consensus Statement J of Vet Intern Med 2016; 30:503-515 p. 508-510.

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INFECTIOUS DISEASES

U.S. Infectious Disease Update: (December 21 to January 22) EASTERN EQUINE ENCEPHALITIS VOLUSIA COUNTY, FLORIDA (JANUARY 11) Confirmed

Exposed

Notes

1

2

Paint gelding; private facility, unknown vaccination status, also infected with WNV

LIBERTY COUNTY, FLORIDA (DECEMBER 22) Confirmed

Exposed

1

Notes Private facility; no quarantine

EQUINE INFLUENZA OZAUKEE COUNTY, WISCONSIN (JANUARY 15) Confirmed

Exposed

1

Notes Vaccinated; voluntary quarantine; under veterinary care

EQUINE INFECTIOUS ANEMIA MARICOPA COUNTY, ARIZONA (JANUARY 20) Confirmed

Exposed

Notes

1

46

Private facility; official quarantine

4

Reported Dec. 24;

SAN BERNARDINO COUNTY, CALIFORNIA (JANUARY 19) Confirmed

Exposed

Notes

7

19

Training facility; Quarterhorse; official quarantine. Index case confirmed positive while residing in Arizona; originated in San Bernardino.

ECTOR COUNTY, TEXAS (JANUARY 12) Confirmed

Exposed

2

Notes Quarterhorse; private facility; official quarantine; both horses euthanized

TRAVIS COUNTY, TEXAS (JANUARY 12) Confirmed

Exposed

2

Notes Quarterhorse; private facility; official quarantine. 2 horses euthanized

EQUINE HERPESVIRUS ALAMEDA COUNTY, CALIFORNIA (JANUARY 21) Confirmed

Exposed

Notes

1

27

Myeloencephalopathy; Thoroughbred; racetrack; quarantine

DODGE COUNTY, WISCONSIN (JANUARY 15) Confirmed

Exposed

1

Notes Respiratory; private facility; voluntary quarantine

DODGE COUNTY, WISCONSIN (JANUARY 15) Confirmed

Exposed

1

Notes Respiratory; filly; private facility; voluntary quarantine

LAMB COUNTY, TEXAS (JANUARY 13) Confirmed

Exposed

1

Notes Neurologic; Quarterhorse; first positive detection of EHM in Texas this year; quarantine

SENECA COUNTY, OHIO (DECEMBER 27) Confirmed

Exposed

Notes

1

15

Neurologic; Quarterhorse mare; boarding facility; quarantine; vaccinated; horse is recovering

20

Issue 1/2022 | ModernEquineVet.com

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INFECTIOUS DISEASES

U.S. Infectious Disease Update: (December 21 to January 22) RABIES MCCLAIN COUNTY, OKLAHOMA (JANUARY 18) Confirmed

Exposed

Notes

1

5

Farm; no quarantine; unvaccinated; euthanized

STRANGLES OKANOGAN COUNTY, WASHINGTON (JANUARY 12) Confirmed

Exposed

1

Notes Horse farm; voluntary quarantine

MULTIPLE COUNTIES, WISCONSIN (JANUARY 15) Confirmed

Exposed

Notes

Unknown

Unknown

Since November, multiple counties reporting voluntary quarantine; recovering. Appears related to rescue horses that were moved around.

LOS ANGELES COUNTY, CALIFORNIA Confirmed

Exposed

Notes

1

2

Quarterhorse; voluntary quarantine; unknown vaccination status; affected and alive

MULTIPLE COUNTIES, FLORIDA (JANUARY 13) Confirmed

Exposed

Notes

3

25

First confirmed case among reports. In 1 case, clinical horse imported from Utah.

DELTA COUNTY, MICHIGAN (JANUARY 3; DECEMBER 28) Confirmed

Exposed

1

Notes Quarterhorse gelding; vaccination status unknown; recovering

LENAWEE COUNTY, MICHIGAN (DECEMBER 28) Confirmed

Exposed

Notes

1

4

Miniature gelding; vaccination status unknown; voluntary quarantine; recovering

SNOHOMISH COUNTY, WASHINGTON (DECEMBER 23) Confirmed

Exposed

Notes

1

11

Private facility; voluntary quarantine

LOGAN COUNTY, OHIO (JANUARY 3) Confirmed

Exposed

2

Notes Private facility

DEFIANCE COUNTY, OHIO (DECEMBER 27) Confirmed

Exposed

Notes

1

2

Halflinger gelding; training facility; vaccination status unknown; recovering

WEST NILE VIRUS VOLUSIA COUNTY, FLORIDA (JANUARY 11) Confirmed

Exposed

Notes

1

2

Paint gelding; private facility; vaccination status unknown. Clinical sign onset in December. Also infected with EEV.

Information gathered from the EDC—Equine Disease Communication Center. Reports occurred between 12/21/21 and 1/22/22.

More information on each case available at https://equinediseasecc.org/alerts

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Issue 1/2022 | ModernEquineVet.com

NEW NOTES

Cellular Receptors Identified for Eastern Equine Encephalitis

Gene-editing screen

For the current study, the researchers first used a CRISPR-Cas9 gene-editing screen to identify a receptor for Semliki Forest virus (SFV) on human cells.

SFV is an alphavirus that can cause severe neurologic disease and death in rodents and other animals.

The receptors that the researchers found for SFV

Under a magnification of 83,900X, this digitally colorized transmission electron microscopic (TEM) image depicts a salivary gland tissue section that had been extracted from a mosquito, which was infected by the EEE virus. The viral particles have been colored red.

Image by Fred Murphy; Sylvia Whitfield/CDC

Identifying a receptor for alphaviruses would give the scientists, veterinarians and physicians a running start on developing tools to prevent, control and treat infections. Harvard Medical School researchers identified a set of cellular receptors for at least 3 related alphaviruses shared across mosquitoes, animals and people.

The researchers tested a “decoy” molecule that successfully prevented infection and slowed disease progression in a series of experiments in cells and animal models, an important first step toward developing preventive and curative medicines.

Understanding the basic biology of a virus's life cycle is crucial to finding a way to prevent an illness, according to senior author Jonathan Abraham, MD, MPH, assistant professor of microbiology in the Blavatnik Institute at Harvard and an infectious disease specialist at Brigham and Women's Hospital.

“Understanding how a virus enters and infects a cell is as basic as it gets,” he said, adding that viral entry marks the beginning of infection, making it a good place to look for preventive strategies and treatments.

The alphaviruses the researchers studied, including eastern equine encephalitis (EEE), have a history of causing deadly, if short-lived, outbreaks, but little is known about how the virus attacks host cells. Only a few other receptors related to infection from alphaviruses have been identified.

EEE, western equine encephalitis (WEE) and Venezuelan equine encephalitis (VEE) are all caused by alphaviruses. Birds and rodents are the primary reservoirs, but unvaccinated horses are particularly susceptible and often serve as sentinels. These diseases are zoonotic. EEE, the most common, is found widely in several regions of the United States, especially where there are high mosquito populations, according to the Department of Agriculture.

The survival rate for horses is poor, about 90%.

were also compatible with EEE and another related virus called Sindbis, which can cause fever and severe joint pain in humans and causes neurological disease in animals and rodents “That's why it's important to study these viruses as families,” Dr. Abraham said. “You can end up studying a virus like SFV and discover something really exciting about the biology of related viruses that has the potential to unlock novel ways to treat new categories of viruses that are capable of causing serious disease and outbreaks.”

As a means of verifying that the receptors were important in causing infection, the researchers conducted experiments with a decoy protein, a molecule with a structure that mimics the receptor and can trick the virus into binding to the drug instead of to the host cell it aims to infect. The molecule, in effect, disables the virus and averts entry into the host cell, preventing infection.

The team's experiments demonstrated that blocking the virus from interacting with the host cell receptor prevented infection of human and mouse neurons.

They also found that the decoy molecule protected infected mice from developing rapidly fatal alphavirus encephalitis—a finding that the researchers said suggests this pathway could be targeted by drugs or antibodies to treat alphavirus encephalitis.

MeV This research was supported by the Department of Health & Human Services, the National Institutes of Health, the Burroughs Welcome Fund, the William Randolph Hearst Foundation, the Brigham and Women's Hospital Harvard Milton Fund , the Vallee Scholar Award and the Howard Hughes Medical Institute.

For more information: Clark LE, Clark SA, Lin CY, et al. VLDLR and ApoER2 are receptors for multiple alphaviruses. Nature. 2021 Dec. 20. DOI: 10.1038/s41586-021-04326-0. https://www.nature.com/articles/s41586-021-04326-0

ModernEquineVet.com | Issue 1/2022

23

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