A research-based look at how changes in the equine influenza virus (EIV) have created a need for a change in EIV vaccines.
Sequencing technology has broadened infectious disease monitoring. Genetic sequencing is a powerful tool for understanding the significance of antigenic drift in the equine influenza virus (EIV) and subsequently determining how well an equine influenza vaccine might protect against a particular influenza virus.
To help shed some light on this subject, Kyuyoung Lee, DVM, MPVM, PhD, discusses his recently published article, “Genome-informed characterization of antigenic drift in the hemagglutinin gene of equine influenza strains circulating in the United States from 2012-2017.” Dr. Lee is a research professor of the department of microbiology in the college of medicine at Korea University, and he led epidemiological research in veterinary medicine for master’s and PhD degrees at the University of California, Davis.
An evolutionary foot race Antigenic drift of EIV is evolutionary biology at its best—for survival, a species must constantly adapt, evolve and rapidly reproduce in the face of competing species. This “Red Queen hypothesis,” as it’s been termed, helps explain that in order to keep one strain of EIV spreading in a horse population, the strain should compete with many other novel variants each season. In this process, transmissibility or survival against the host’s immunity are key factors in determining the compatibility of each strain. If one strain dominantly spreads in one season, the dominant strain will reproduce many novel variants rooted on its own genetic characteristic. These novel descendants will compete again in the next season.
As EIV continuously repeats this process, the EIV strains accumulate mutations in key antigenic sites, such as the hemagglutinin (HA) or neuraminidase gene, which can possibly affect their transmissibility or survival against the host's immunity. We call this antigenic drift: the continuous accumulation of genetic mutations over time in key antigenic sites through the natural selection.
Many studies of influenza virus revealed multiple key antigenic sites in the HA gene. One significant study is Woodward et al (2015),1 which mapped key antigenic sites in the HA protein structure of EIV H3N8. The study found that even though EIV vaccines were widely used in the global horse population, EIV epidemics occurred seasonally, and the epidemic EIV strains had unique genetic differences in key antigenic sites in the HA gene compared with vaccine strains. Considering that antigenic drift selects novel EIV strains that are able to avoid hosts’ immune response (either naturally infected or vaccine induced), we can infer that EIV strains with genetic changes in specific key antigenic sites in the HA gene would have higher compatibility than other strains.
Conventionally, antigenic modifications of EIV strains were evaluated by serological tests, such as the Haemagglutination test comparing vaccine and wild type strains. Current sequencing technology allows us to collect nucleotide sequences of pathogens much faster and easier. Thanks to this development, our study collected nucleotide sequences of the HA gene of EIV strains in samples provided by equine veterinary practitioners from EIVinfected U.S. horses from 2012-2017. We concluded that
antigenic drift of EIV was the most probable cause of the increased incidence of influenza vaccine failure in the U.S., as opposed to the introduction of foreign EIV strains.
Continued monitoring through genetic sequencing of dominant wild EIV strains is an essential practice for not only understanding what’s circulating but, as important, developing vaccine strains to combat these novel EIV variants infecting horses.
This video shows how evolving EIV reduces vaccine antibody binding at key immunodominant sites of the hemagglutinin glycoprotein.2,3
Through the Equine Respiratory Biosurveillance Program, only Merck Animal Health continues to sequence influenza isolates to evaluate whether commercially available vaccine strains— including our own Florida ´13—provide adequate protection against today’s circulating field strains of influenza.
Only Florida ´13 aligns with the EIV circulating today in horses. Only PRESTIGE® vaccines from Merck Animal Health contain Florida ´13.
With some infectious diseases peaking in the fall and winter months, now is the time to ensure your clients remain vigilant. These talking points will help you communicate the importance of vaccinations and biosecurity.
Infectious diseases including equine flu and equine herpesvirus-4 (EHV-4) ramp up in the fall and winter months. Keep these key facts in mind to help ensure your horse is protected with up-to-date vaccinations and thorough biosecurity measures around your farm and on the road.
• EHV-4 is the most common culprit of contagious equine disease outbreaks.3
• Equine flu season extends from December through April.3,4
• Equine flu evolves like human flu but much slower. That’s why using an updated vaccine that accounts for the most recent flu strains is important.
• Infectious diseases spread with or without travel. Even horses who don’t leave the barn are at risk of equine flu and EHV-4, particularly if other horses coming and going.
• Vaccinate all horses in the barn whether traveling or not.
• Monitor your horse's temperature twice daily while traveling to catch early signs of infectious disease.
• Segregate different populations, such as traveling and resident horses, to manage introduction of disease.
• Quarantine new horses for a minimum of two weeks before introducing them to the resident herd.
• Practice good hygiene, such as regularly cleaning and disinfecting tack, equipment and stalls, and washing your hands after handling each horse.
• Minimize nose-to-nose contact and avoid use of communal equipment and water sources.
• Immediately isolate horses with nasal discharge, cough, fever or diarrhea from other horses and have them examined.
that because he was smaller, he decided he’d show them from the very beginning that he wasn’t to be trifled with.
This horse that did everything I ever asked of him, helped raise two of my kids and gave countless others a safe experience. I haven’t had a horse with a bigger heart. I had to put him down a few years back at the age of 18. I buried him here on the place in a little grove of trees. We were lucky to have him, he was a good one!
This installment of Ron’s Campfire is an original piece written by Ron McDaniel, National Equine Sales Director for Merck Animal Health.
I’ve been fortunate to have had a few good horses. I’m no horse trainer, but through the years I’ve used horses for various jobs and competitions. If I was to narrow it down to one of my favorite horses, it would have to be an unregistered Paint horse named Jazz. He was kind of a scrawny 2-year-old that my preacher owned, when I traded a two-horse trailer for him. We started him under saddle, and in no time he became my daughter Nikki’s main mount. She and her sister Michelle were not teenagers yet but were competing with the big kids in local horse shows. Jazz soon became Nikki’s barrel and pole horse, and the two of them made it to the State Finals in Arkansas.
In those days, I was team roping quite a bit so every horse we had was used in the practice pen to rope steers. Jazz was not a big horse. He might have been 14.2 hands on a good day, but he was stout and had lots of heart. We started heeling on him and before long, he was the “A” string heeling horse for a neighbor boy that went to ropings with us.
Jazz also was a using horse when we worked cattle for neighbors or went to brandings. That little horse did it all… brandings, gathering cattle, barrels, poles, overnight trail rides, and heeling. He was even the mount Nikki rode to the runnerup Siloam Springs Rodeo Queen title. Once Nikki went to college, he became the mount for our son Chay, who was 10 years younger than Nikki. He was a great first horse for Chay and was the horse we’d put inexperienced adults or kids on.
He was great around people, but one of his few vices was how he went about establishing the pecking order around new horses. He’d eat them up. I believe
There are no greater stories to be told than those of the practicing equine veterinarian. Pull a chair up to Ron’s Campfire to read some of the best from equine veterinarians who not only have scientifically gifted minds, but also are talented writers and storytellers.
If you have a story or blog you’d like to share, we’d love to feature it. Please email Ron McDaniel to learn more or to submit contributions.
A veterinarian’s best healthcare recommendations are only as good as the horse owner’s inclination to follow them. And sometimes horse owners listen to their trainers as much as their veterinarians. Follow these steps—based on Merck Animal Health Senior Equine Professional Services Veterinarian Dr. Philip van Harreveld’s experience working with trainers over the years—to encourage horse owners and trainers alike to carry out care that nets the best outcomes for your patients.
1.Engage in simultaneous communication. Involving both owner and trainer in all communications avoids misunderstandings and potential shortcuts to care.
2. Focus on the horse. Centering all conversations and considerations on what’s best for the horse’s health helps keep everyone directed toward the same goal. If trainers are tempted to look for shortcuts to keep the horse competing, help them set realistic expectations with the owners by emphasizing the importance of addressing health concerns to stay focused on what’s in the horse’s best interest.
3. Announce a follow up. After you make a strategy for the horse’s care, let the owner and the trainer know you will check in with them both in the near future to see how the horse is progressing. Trainers are more likely to follow the plan when they know there are upcoming checks and balances.
When Addie Reinhard, DVM, MS, graduated from the University of Tennessee College of Veterinary Medicine in 2015, she barreled enthusiastically into full-time practice in Lexington, Kentucky. But, like many of her early-career veterinary peers, she encountered discouragement and disillusionment within her first few years.
“I can pinpoint two specific times of severe burnout in my early career,” Dr. Reinhard says. “Fortunately, I had some phenomenal mentors, both in and out of the practice, who helped me through.”
That experience prompted Dr. Reinhard to go back to school at the University of Kentucky to study veterinary wellbeing. She spent two years researching early-career wellbeing and piloted a professional development program for veterinarians that yielded promising evidence of its effectiveness (see chart).
Using what she’d learned, Dr. Reinhard created MentorVet in 2021, with the aim of transforming veterinary medicine into a healthy profession for individuals and communities.
Markers of wellbeing rose for veterinarians who went through Dr. Addie Reinhard's program compared with those who did not, while stress, cynicism and exhaustion decreased.
MentorVet is a program designed to help early- career veterinarians navigate the up and downs of their chosen profession assisted by evidence-based research. Participants take a five-module online course designed to help them develop wellbeing strategies for their entire career. In addition, they gain access to:
• A virtual small peer group that meets monthly
• A private social media app
• A financial coaching session
• Mentorship from a veterinarian trained in suicide prevention and emotional support
• An optional session with a mental health coach.
Participation in MentorVet has doubled since its launch, from 75 veterinarians to 150. Dr. Reinhard expects that number to double again, with an anticipated 300 to 500 veterinarians enrolling in the next cohort.
This growth, she says, wouldn’t have been possible without Merck Animal Health. “They found out what I was doing and wanted to support me,” she says. “So they became a founding sponsor and have been helping me grow so we can reach the veterinarians who need it most.”
Besides helping her make industry connections, Merck Animal Health has provided funding, marketing support, mentorship and scholarships. MentorVet is also closely tied to the Merck Animal Health Veterinary Wellbeing Study series, with Dr. Reinhard acting as a collaborating researcher.
Equine participation in the MentorVet community has been increasing. Dr. Reinhard is excited excited, particularly since early-career equine veterinarians face unique challenges.
“Equine veterinarians may work in smaller practices, work longer hours, and are on call more often,” she says. “They’re going from a giant support network of students, faculty members and other veterinarians to maybe just one or two people, so it can become isolating.”
Dr. Reinhard hopes the support network equine veterinarians develop through MentorVet will help them navigate those challenges and stay connected. Members of the Merck Animal Health team are excited about what MentorVet is doing for equine veterinarians.
“I am currently a mentor with MentorVet, and it’s been a great experience,” says Chrissie Schneider, DVM, MS, DABVP (Equine Practice), Senior Equine Professional Services Veterinarian. “It’s crucial that we equip equine practitioners with the tools they need to have a healthy and long career in equine practice, and I’m excited that Merck Animal Health is part of it.”
Her colleague Duane E. Chappell, DVM, Associate Director for Equine Pharmacovigilance & Veterinary Professional Services, also a MentorVet mentor, concurs. “Continuing to make these kinds of resources available to newer members of our equine veterinary community is incredibly important to the future of our profession,” he says.
As Dr. Reinhard broadens the MentorVet program to reach veterinarians who are further in their career along with other members of the veterinary team, she’ll continue to gather evidence of effectiveness and use her research results to maximize its impact.
“I am grateful for Merck Animal Health’s support and for all the people who have helped me and MentorVet along the way,” she says. “Something like this doesn’t happen alone.”
To learn more or get involved in MentorVet, visit www.mentorvet.net.
Raleigh, North Carolina
philip.van.harreveld@merck.com
Tell us a little bit about your horse background.
I grew up in Brazil and, after following an initial career in engineering based on my airplane and flying background, I transitioned over to veterinary school after losing a beloved mare to colic on my parent’s horse farm. The desire to focus on equine surgery was rooted in wanting to be able to save horses from terminal colic illness.
If you were a horse, what type of horse would you be?
A reliable, easygoing jumper. I like sports, but I tend to stay calm under pressure.
Best horse advice you’ve ever received?
Horses are not four-wheelers. They have feelings and emotions just like we do. Be gentle with them and give them time when things are not going well.
Outside of the equestrian/veterinary world, what is your favorite hobby?
Fishing, volleyball or pickleball.
How long have you been working for Merck Animal Health?
Since May 2022.
What is your favorite part of being on the equine veterinary professional services team?
The people: I get to work with a very caring group of colleagues who are always looking out for what is ultimately the best for the horse.
If there were one thing you would want customers to know about you, what would it be?
Every time I treated a very sick horse as a veterinarian, I gave it my all despite difficult situations.
Lafayette, California
cara.wright@merck.com
Tell us a little bit about your horse background.
I grew up outside of Washington, D.C., and started taking riding lessons when I was 5 years old. My first lesson was on a little Appaloosa pony named Cupcake and I remember being so scared that my parents had to force me to go back to horse camp because they had already paid for it. I dabbled in eventing and small local shows and always knew I wanted to be an equine vet.
If you were a horse, what type of horse would you be?
I would be an OTTB: Relatively athletic and game to try anything. It might not always be pretty, but I will get it done well and with a lot of heart.
Best horse advice you’ve ever received?
Take time to greet them when you meet them. If they are not doing what you want, step back and ask again in a different way, because they are likely just not understanding the way you are asking.
Outside of the equestrian/veterinary world, what is your favorite hobby?
Triathlon! I love training and challenging myself. Racing has given me the chance to travel to some beautiful places that I
may not have visited otherwise, like Italy, Croatia and Coeur D’Alene, Idaho. Triathlon has taught me how to use process goals to measure success, as opposed to just always marking success as getting a certain time or making it onto the podium. The best race prize I ever received was a potato from a race in Idaho called the Spudman.
How long have you been working for Merck Animal Health?
I started just a few months ago, in June to be specific. The team and our clients have been so welcoming.
What is your favorite part of being on the equine veterinary professional services team?
I am so excited to be a part of a team that is dedicated to serving others in our profession. The team has a broad scope of experience that we can all pull from to learn from each other and help our profession grow.
If there were one thing you would want customers to know about you, what would it be?
I love meeting people and hearing their stories, so please reach out and say hi.