One of the best places for a disease to spread is to be in an active, stressful location. So, when equine herpesvirus (EHV) is detected at a racetrack, it can spread faster than a turf sprinter if the right precautions aren't taken.
In the days building up to the start of Fonner Park's 2022 racing season, a horse presented clinical signs of EHV-1. This wasn't the first time that the Nebraska racetrack had experienced the potentially deadly disease, so officials were quick to set up a quarantine around Barn R.
“We had an outbreak six or seven years ago, and Dr. [David] Radechel and the health department did a great job of shutting this episode down quickly,” said Tom Sage, executive director of the Nebraska Racing and Gaming Commission.
Radechel is a state veterinarian for the Nebraska commission, which put him at the helm of the state's response to the 2022 outbreak.
“In our favor, (Barn R) is already set away from the others here at Fonner, so we had that advantage [for better quarantine practices],” said Radechel. “We hoped that the isolation in a far barn would help in the containment.”
Two horses had already been euthanized from advanced clinical signs of equine herpesvirus myeloencephalopathy (EHM), the neurologic form of EHV-1. Radechel and Fonner Park officials were hoping to prevent any further losses.
They didn't know that help would be coming to them from a Kentucky veterinarian's previous work with raccoons.
Dr. Rob Holland, a well-known veterinary immunologist based in Lexington, had used AniCell products to combat resistant wound infections and was familiar with the inherent antimicrobial properties of amnion.
EquusCell is a product of AniCell, which is derived from all-natural amnion tissue-based products for horses. All living things were grown from amnion tissue and science has shown that a fetus doesn't just grow from the inside out, but also grows from the outside in, utilizing the amniotic material to aid in the single greatest growth spurt any animal will see. AniCell uses this technology to address tissue-based injuries in horses and dogs.
Holland was curious to explore the impact of amnion products on infectious disease in racoons at the Kentucky Wildlife Center, since the amnion unit protects the developing fetus from infectious disease during pregnancy and can heal the fetus from untoward effects of infections. Holland wanted to see what the all-natural regenerative product would do for parvovirus in raccoons, both in terms of controlling the infection and intestinal damage caused by the virus. The findings were exciting — the product kept the raccoons from succumbing to the usually deadly disease and repaired the intestinal damage, helping them to recover.
It was happenstance that Brandon Ames, founder and president of AniCell Biotech, and Dr. Tammi Epp reached out to Dr. Angela Pelzel-McCluskey of the USDA.
“We talked with Dr. Angela Pelzel-McCluskey with regards to what we should be screening for in the onboarding process of donor mares into our foaling facility in Arizona to ensure product safety,” recalls Ames. “It was a side conversation regarding the capabilities of amnion and what the product was used for that brought forth the antimicrobial properties of amnion, Dr. Holland's work and the possibility of helping with the company's amnion technology being able to help curb EHV-1 outbreaks that currently had no medical solution.”
Pelzel-McCluskey is an epidemiologist for the USDA-APHIS and her role requires her to track infectious diseases in horses. She had long wished for a product that could be sprayed up the horse's nose to stop the shedding of EHV-1 when there's an outbreak to block the spread. In her discussion with Ames, she wondered whether AniCell could protect a horse's respiratory tract from viral illness the same way it could protect and heal a raccoon's gastrointestinal tract. Based on nasal administration science that AniCell had done in 2018 for use on racehorses that bleed through their nose during racing, Ames did not believe this was the best route of administration for the product. Instead, he recommended the product be given subcutaneously to try to combat EHV.
“I've tried other types of treatments for EHV-1 in the past, but Brandon had told me about a horse in California who had been exposed to an EHV-1 outbreak and was just starting to show clinical signs,” said Pelzel-McCluskey. “A few days after the first injection of AniCell's product, the horse was clinically normal.”
The best way to test this product was to find an outbreak. Then, Pelzel-McCluskey got a phone call from Nebraska alerting her to an EHV-1 outbreak at the racetrack. Pelzel-McCluskey reached out to Nebraska's State Veterinarian, Dr. Roger Dudley, who had just placed the racetrack under quarantine with a plan.
“Dr. Tammi Epp, our Senior Scientist and Technical Veterinarian for AniCell, designed a protocol to test 60 head, and follow their response with virus detection diagnostics and other testing to determine the success in minimizing the outbreak, but when we arrived, our treatment pool had expanded to 112 horses,” said Ames. “When we arrived, there were two dead, two that were neurologic, and the rest had been exposed.”
Radechel, Epp and Pelzel-McCluskey, along with Ames, worked together along with the Fonner Park horsemen and others to tackle the outbreak. Radechel collected blood samples from horses in the quarantined barn prior to AniCell's arrival and helped with testing. Nebraska's Department of Agriculture and the Nebraska Racing and Gaming Commission set the boundaries for the quarantined barn, added isolation barn, and held meetings with the horsemen.
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If you appreciate our work, you can support us by subscribing to our Patreon stream. Learn more.“The horsemen were a little apprehensive for some potential costs and any side effects to the horses,” said Radechel. “It came down to having nothing to lose, other than additional horses and the potential of being trapped at the track a long time. So, we thought it was worth a shot.”
The plan went into action. Pelzel-McCluskey gave parameters for the horses in the other barns and still in training. The racing commission and track took input from the company and Pelzel-McCluskey and made it all work in a beneficial way for the horses and horsemen. The company gave the product injections at a very discounted rates, did pre- and post-treatment testing.
The veterinary team used a two-dose protocol of EquusCell at Day 0 and Day 4, given to horses in the quarantined barn at the start of the outbreak. They hoped the treatment would kick the immune system back to a healthy level with the strength to address the virus.
One of the highlights of the quarantine was when one horse in quarantine went down with neurologic symptoms. Veterinarians feared that the mare might be the third casualty to the disease.
“She was extremely frightened, and we thought we would have to euthanize her because she was in such bad shape,” Pelzel-McCluskey recalled.
Ames was determined to help the mare. On the third day, the mare had improved in all ways, including the neurologic exam. Within five days from her first treatment, she was considered “almost normal” in her exams. Workers created a small pen in the back of the isolation barn for the mare, and she was jumping around and cantering in the pen.
“It was crazy. She was initially Grade 4 (on the neurologic evaluation), and her recovery was impressive,” said Pelzel-McCluskey. “I was wrong on the impact it can have on neuro horses. It really helped her.”
This was another surprise beyond the antiviral properties of the product – veterinarians are hopeful that this mare's improvement means AniCell's regenerative capabilities could help minimize damage, protect neurologic tissue, modulate the inflammation and help revascularize and repair the damaged tissue in the midst of neurologic disease. They noted the pathology of the neurological form of EHV has been likened to ischemic stroke in humans, and amnion has been noted to have positive effects in improving stroke recovery.
A few months after the outbreak, the filly ran in a race at Canterbury Park and won.
In the end, horses were saved and the time for quarantine was cut shorter than if nothing had been done. Fonner Park horsemen practiced high-level biosecurity practices before, but Radechel and the horsemen instituted even stricter polices throughout the quarantine.
“We utilized a second barn as a second-degree quarantine, and as soon as a horse tested positive in the first quarantine barn (Barn R), we moved that horse to the second barn,” said Radechel. “We tested on a regular basis until everything came back negative and the assay levels showed the infection dropping, titers were on the decline in a short period of time.
Additional and unexpected results included the prevention of further spread beyond the horses initially infected, reduction in the virus reaching the bloodstream, which is prerequisite to the development of the neurologic form of the disease and more horses succumbing to the infection, and a possible impact on the ability of the virus to persist within an infected horse. In the Fonner Park outbreak, AniCell veterinarians had found that the virus had been eradicated and the spread had ceased, on average, in 2.3 days.
“The second level quarantine barn helped,” Radechel said.
Authorities at Fonner Park did not allow horses from the infected barns to continuing working through the quarantine.
“It didn't make sense to me that if you have a horse in that barn where the virus has killed two already that you'd want to stress your animal more,” Radechel said. “So, I told [horsemen] they could walk in individual walkers while their stalls were cleaned, but that was it. Then there was disinfection, cleaning and good biosecurity was demanded of everyone involved.”
Radechel and Sage were quick to praise the horsemen for their hard work and flexibility during the outbreak.
“We really had the greatest teamwork with the Nebraska Department of Agriculture, Fonner Park, racing officials and the members of Brandon's team,” said Sage.
Now, a year later, Pelzel-McCluskey and the researchers at AniCell are still looking through data and looking for more outbreaks to test the product.
“We're still looking at data, and we'd like to get more data,” said Pelzel-McCluskey. “(With EHV-1,) it's an all or nothing thing — we need every horse that is exposed to stop shedding. We know that if you can get this in them early in treatment, in the neurologic patients, we have had some great success. So, that's a positive.”
This was the largest and most detailed field study for this product. From here, AniCell will begin testing the validity of findings from this field study in scientifically-controlled experiments conducted by university experts.
“This technology is definitely novel with the antiviral, immunomodulating, and regenerative properties that this upcoming future research will help us better understand,” said Epp.
However, Pelzel-McCluskey knows there's still so much work to be done before EHV-1 can be fully controlled.
“We don't have a way to prevent outbreaks right now — you can't stop the index case because all of the horses have seen this virus by the time they are two years old,” she said. “The horse is carrying herpesvirus for life. If at any given time, when he's stressed, the horse can start shedding the virus. Most of the time the horse is fine and looks clinically normal. The majority aren't causing outbreaks but at any given moment a horse can start shedding. We don't have anything that stops the intermittent shedding in a horse population, like a racetrack.”
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