A Texas peek into a complex topic
By Jade Currid
Photos by Bud Force
Regular vaccinations are an essential part of preventative care for our equine partners to remain healthy, active, and performing at their best whether they are at home on the ranch or away at an event.
Dr. Leslie Easterwood, who serves as a Clinical Assistant Professor of the Equine Community Practice Department of Large Animal Clinical Sciences at Texas A&M University, discusses the basics of core and risk-based equine vaccinations.
“There are several basic vaccines that all horses should get – Rabies, West Nile, Eastern, and Western Encephalomyelitis, and typical Tetanus is included with that,” Dr. Easterwood said. “And, then there are some risk-based vaccines, that we still consider core, but we take into account the possibility for exposure, and those are for the Influenza/Rhinopneumonitis (Flu/Rhino) and Strangles.
Horse owners in most states should administer the EWT vaccine twice a year to prevent Eastern and Western Encephalomyelitis, Tetanus, and West Nile, according to Dr. Easterwood.
However, horse owners in states with a true winter are more than fine to administer the EWT vaccine only once a year.
“Down here in the South, where we have mosquitoes year-round, the EWT equine vaccine should be administered every six months to prevent insect-borne diseases,” said Dr. Easterwood.
Horse owners should administer the Rabies vaccine once a year and the Flu/Rhino and Strangles vaccines two to four times a year depending on their horse’s exposure.
“If you think about the category of say, a three-year-old racehorse in training that’s moving across the country that’s traveling a lot and is highly stressed – that horse is probably going to be exposed to lots of different horses,” Dr. Easterwood said. “That horse is probably going to receive a Flu/Rhino vaccine four times a year as opposed to the ranch horse that lives on the ranch, doesn’t travel very much, and might be exposed to some day-working cowboys who bring horses over or something like that. Those ranch horses may get by with receiving the Flu/Rhino vaccine twice a year.”
Continued Vaccination is Key in Staving off Equine Disease
According to Dr. Eastwood, improved vaccines that last longer are available on the market. However, no new types of equine vaccines currently exist.
“Now, there are a lot of mRNA vaccines that are kind of in the works, similar to the Covid vaccines, that may over the next couple of years give us some better vaccine technology,” Dr. Easterwood said. “But, at this point, we really haven’t changed vaccine technology.”
A top priority for horse owners is ensuring their horses are vaccinated, according to Dr. Easterwood.
“Think about the West Nile Virus,” Dr. Easterwood said. “We know that the West Nile Virus is relatively rare in horses these days. We see one or two horses per year affected with West Nile as opposed to those years spanning from 1999 to 2001 when we first had West Nile in the U.S. We were losing horses to the West Nile Virus, and it was a big outbreak. We know that now we rarely treat the West Nile Virus, and it’s typically in an unvaccinated horse.”
The severity of the effect of the West Nile Virus on the equine population has decreased significantly due to continued vaccination.
“And, we know that the West Nile Virus is still here,” Dr. Easterwood said. “It’s not a change in the disease because we don’t have a vaccine for the West Nile Virus in people. And, we know that we still have the same number of people coming down with the disease as we did back then. So, just getting vaccinated and ensuring that happens is so important.”
Refer to the American Association Equine Practitioners Vaccination Guidelines and Form a Plan with Your Veterinarian
Four Sixes Ranch Associate Veterinarian Dr. Nathan Canaday emphasizes that all horse owners should refer to the American Association of Equine Practitioners (AAEP) guidelines for imperative information on core and risk-based vaccines.
“That’s kind of the gold standard,” Dr. Canaday said. “I agree with the recommendations for the core vaccines, which are for the Eastern and Western Encephalomyelitis, Rabies, Tetanus, and West Nile. I think all horses are at potential risk for those particular diseases. Then they have risk-based vaccines, and there’s a long list of those. They have them on their website, and you don’t even have to be a member to look at them. You can google American Association of Equine Practitioners vaccination guidelines.”
Not every horse needs all of the risk-based vaccines, according to Dr. Canaday.
“Yes, I’m pro-vaccine and a big fan of them, but also you can go overkill, and/or you don’t have exposure to them,” Dr. Canaday said. “So, my second big point I want to emphasize is having a good relationship with a veterinarian in your area. That way you can work through a protocol for your horses and what they’re exposed to.”
Dr. Canaday said he understands the business decisions that ranchers have to make concerning their cattle and horses. The rattlesnake vaccine is a risk-based vaccine that might not be economical for a rancher to administer to their horses depending on the size of their herd. Few out of a herd of 500-800 horses incur a rattlesnake bite at the Four Sixes Ranch per year. If a horse on the Four Sixes Ranch receives a rattlesnake bite, Dr. Canaday and his colleagues treat the affected horse with an extremely effective rattlesnake antivenom plasma, which he refers to as the gold standard treatment.
Since all horses are vaccinated differently according to age, sex, and risk to a certain disease, it is especially important for a horse owner to partner with their veterinarian to determine what type of vaccination their horse needs.
A lot of horse owners are starting to travel again to a variety of events and venues after their horses may have been sequestered or have not traveled for a year or two due to circumstances resulting from Covid. These owners should also discuss vaccines with their veterinarians.
“Have that discussion with your vet on risk-based vaccines, especially for the highly contagious diseases like the Equine Herpesvirus, the Influenza, the Strangles, and so on,” Dr. Canaday said. “You want to make sure your horses are well-vaccinated, so you don’t start traveling and going to these different events, and then come back to your working ranch and accidentally get your entire herd exposed.”
Horse owners, who plan on traveling across the country, should vaccinate their horses three to four weeks before embarking on a trip.
“Some horses’ immune systems are knocked down for a week or two after being vaccinated,” Dr. Canaday said. “And, the vaccine doesn’t protect you for the first week or two anyways.”
Dr. Canaday says he has received the impression that unfavorable sentiments toward the Strangles vaccine exist.
“We administer the Strangles vaccine because we are a large breeding farm, a large ranch, and a lot of horses come through,” Dr. Canaday said. “And, since we’ve been using it, we have seen a huge decrease in the incidence of Strangles and severity of Strangles, and I highly recommend it.”
It took a couple of years of horses receiving the Strangles vaccination at the Four Sixes Ranch before Dr. Canaday noticed a notable decrease in the disease.
“By the time they’re three years old, they’ve had three rounds or more of that vaccine,” Dr. Canaday said. That made a huge difference in the number of sick horses by building that immunity in those younger populations.”
The Four Sixes Ranch ceases vaccinating horses for Strangles when they reach eight years of age. Legendary Four Sixes Ranch Horse Division Manager and head veterinarian Dr. Glenn Blodgett formulated the cut-off age for vaccinating a horse for Strangles at eight years old, according to Dr. Canaday.
Ranchers should factor all angles when it comes to vaccinating their horses and maintaining optimal herd health.
“We live in a big ranching country right here,” Dr. Canaday said. “There’s a lot of day workers that come around. And, so you may have a closed herd, and you might not go to ropings and different events, but as soon as you start having those day workers come in, your herd is potentially exposed to the disease. With just the nature of their job, their horses are everywhere and usually are carrying some sort of bug, mostly Strangles-related. So, to me, it’s highly worth starting. Even if you think you’re just a little closed herd ranch, I’d highly recommend vaccinating for those infectious diseases, such as Equine Herpesvirus, Rhino, and Strangles.”
Dr. Canaday Talks Four Sixes Ranch Equine Vaccination Protocol
Dr. Canaday says the key to a top-notch vaccination regime is being organized. The Four Sixes Ranch uses a computer program to assist in coordinating vaccines.
“We put reminders in for every horse, and we vaccinate them when they are in the right age groups,” Dr. Canaday said. It’s quite the undertaking, but we have the infrastructure set up for it.”
As a part of vaccine protocol, Dr. Canaday and his colleagues perform chest scans on all of the foals at five, seven, and nine weeks of age to check for Rhodococcus Equi Pneumonia. At their nine weeks chest scan, the foals receive their first dewormer and Anthelcide to prevent the transmission of Ascarids (roundworms).
“Then we begin vaccinating at 13, 16, 19, and 32 weeks of age, and we kind of spread out the vaccine,” Dr. Canaday said. So, for example, at 13 weeks, we give them that first Strangles vaccine, because to us that’s extremely important. But, that’s a modified live vaccine, and, so it’s kind of a strong one, so we like to give it by itself. And, then three weeks later, at 16 weeks, we administer the booster for the Strangles vaccine. Since their immune systems are already kind of processing that, we go ahead and then add in the West Nile combination, the Eastern and Western Encephalomyelitis and the Tetanus and the Flu/Rhino vaccines.”
Dr. Canaday administers the West Nile combination vaccination booster to foals at 19 weeks of age. Then, the Four Sixes Ranch foals receive another dewormer followed by more immunostimulants.
“The reason we do that is that is right about the time we brand them and wean them and halter break them,” Dr. Canaday said. “And, since that can be kind of a stressful process, we like to give that little bit of booster then.”
Dr. Canaday and his colleagues administer annual vaccines to colts, fillies, and yearlings, primarily sticking with the core vaccines.
Remuda and broodmares
The saddle horses at the Four Sixes Ranch receive the Flu and Strangles vaccines in early spring and the Core EQ Innovator ™ vaccine manufactured by Zoetis in the summer, which is the first and only equine vaccine to help prevent all potentially fatal equine diseases, including West Nile, Eastern, and Western Encephalomyelitis, Tetanus and Rabies. They receive the Flu/Rhino vaccine as well.
Dr. Canaday and his colleagues follow the AAEP guidelines when it comes to vaccinating pregnant mares on the Four Sixes Ranch. At five, seven, and nine months of pregnancy, Four Sixes mares receive the vaccination for Equine Herpesvirus.
“Just to be safe, we also vaccinate our pregnant mares for Equine Rotavirus, as well as Leptospirosis and Salmonella,” he said.
Dr. Canaday says that when he is visiting with ranchers who own broodmares, he advises them to ensure their broodmares receive their annual vaccinations, including the Flu/Rhino, West Nile, and Rabies vaccines.
“If you’re going to administer any additional vaccines such as the Rotavirus, at the very least, give the annual vaccinations one month before foaling because that helps stimulate the mare’s immune system right at the time that she’s making colostrum for the baby,” Dr. Canaday said. “And so, they’ll get big returns by doing that vaccination at that time. It’ll just pay off in dividends in colostrum – because that stuff is liquid gold.”
In addition to receiving the core vaccinations, Four Sixes Ranch stallions receive vaccinations for Equine Viral Arteritis (EVA).
“There’s not a lot of it around, but it’s one of those sexually transmitted diseases that can affect stallions’ semen,” Dr. Canaday said.
Dr. Canaday noted that stallions need three weeks of rest from breeding after receiving the vaccination for EVA.
Although there are currently no new updates on equine vaccination protocol to report, Dr. Canaday says that various universities and research groups are currently working toward advancements in equine vaccines.
“They are working in particular on a vaccine to prevent Rhodococcus Equi Pneumonia in foals,” Dr. Canaday said. “We’ve helped them do some research here. There are some companies and individuals still trying to find new vaccines to help with some of the pesky pathogens we deal with, such as Rhodococcus Equi Pneumonia.”
Experts in many facets of the equine industry are collaborating on effective methods to maintain herd health collectively. A plethora of technology, resources, and friendly faces willing to share invaluable knowledge are readily available to all types of horse owners. Next time you have a chance to talk to your local veterinarian, discuss forming a vaccination plan that fits the specific needs of your horse or herd.