Equine Vaccines Do Best When In Vets’ Hands

Veterinarians must convince equine owners that excising vaccines from their budgets can hurt.


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Tom Judd, DVM, owner of Equine Veterinary Service in Freeport, Maine, says a small but growing portion of his client base insists on buying equine vaccines over the Internet.

“Typically, we tell our clients that vaccinations not purchased though veterinarians can’t be assured of the quality and proper handling of the vaccine before the client gets it in his hand,” Dr. Judd says. “There are too many variables for quality and proper handling.”

Judd continues to promote his “spring visits” as not only a farm call to vaccinate horses but also to build the valued relationship of veterinarian, client and patient.

Veterinarians must convince equine owners that excising vaccines from their budgets can hurt, says Hoyt Cheramie, DVM, MS, Dipl. ACVS. Environmental pathogens—borne by mosquitoes, flies, rodents, air and feed sources—as well as infectious agents transmitted horse to horse can cause potentially fatal consequences.

“Vaccinations are simple, cheap insurance relative to the potential consequences of having a horse get infected with the disease,” says Dr. Cheramie, a large animal veterinarian with Merial Ltd. of Duluth, Ga. “Discuss with owners and clients that it is possible to be financially prudent and still protect the horse.”

Horses that travel will always be more susceptible to disease than those who stay in the backyard. Cheramie reminds veterinarians to educate owners not only about what vaccinations they need at home, but also to research what outbreaks have occurred around their travel destination.

“Help owners understand that you are just as concerned that they don’t spend money on unnecessary vaccines,” he says. “Letting them know that you want them to get more value for their money is good for building client relationships.”

Vaccines by Region

Regional vaccinations make sense to many veterinarians.

For instance, practitioners along the Mexico border will vaccinate for VEE, while equine veterinarians in New Hampshire may opt not to because of so little risk in that area.

Cheramie says a new website—Outbreak-Alert.com—educates veterinarians and their clients as to outbreaks in their regions, right down to their neighborhoods. Reported cases are tracked for horses, cattle, dogs and cats, raccoons and humans as well as mosquitoes and avian sentinels.

Veterinarians may register to stay up to date on reported cases of rabies, WNV, EEE, WEE, influenza, EHV and PHF. Alerts may be emailed or texted to notify practitioners and clients about the equine diseases circulating in the environment.

The website tells owners why their horses should be vaccinated, so veterinarians can use it for educational purposes and for marketing, Cheramie says.

Cutting Costs Can Cost

Today, it is not so much that exposure to these diseases is increasing, he says, but rather that the number of horses being vaccinated for those diseases is decreasing because of purse-tightening among owners.

Some diseases have few outbreaks, but the fact that horses usually don’t recover easily from the diseases should prompt owners not to want to take the risk. He said a horse owner in Indiana recently lost five unvaccinated horses to a suspected botulism-contaminated feed source.

“That’s not just a monetary loss, it’s an emotional one,” Cheramie notes. “Vaccination could have likely prevented that outcome.”

Judd sometimes can get insistent do-it-themselves owners to purchase the vaccines from his practice rather than online.

“We want them to both have better quality vaccines and support local business,” he says.

“From what I understand, vaccines end up in the hands of the catalog companies via veterinarians who, working in tandem with the companies, facilitate the purchase of the vaccines in large quantities,” Judd adds.

“We have to police our own” to stop this sales method, says  Wendy Vaala, VMD, Dipl. ACVIM, a senior equine technical service veterinarian at Merck Animal Health.

Cheramie cautions that, as a rule, animal health companies usually will stand behind any vaccine administered by a licensed veterinarian but typically will not provide support for any treatment required for adverse reactions or lack of efficacy when an owner administers the vaccine.

In Maine, rabies vaccines must be purchased and administered by a licensed veterinarian.

“While we are giving the rabies vaccine,” Judd says, “most of our owners have us vaccinate for everything else while we are there.”

Other Diseases

Rabies is a considerable problem in Maine and in many other areas of the United States because of a large wild animal population living in proximity to domestic animals.

Veterinarians practicing in the Northeast and Midwest—areas in which deer ticks carrying B. Burgdorferi infection are common—are occasionally vaccinating against Lyme disease. Because no licensed equine vaccination is available, practitioners are using dog vaccines against Lyme disease in New York, the Eastern Seaboard, Pennsylvania, Minnesota and Wisconsin, among other states. 

“I almost never see a negative test (when symptoms are present),” Judd says. “Maybe one out of 100 will be negative.”

“The call for a Lyme disease vaccine in the Northeast, and now in the Midwest, is huge,” Judd adds. “But we’ve heard for years that the vaccine companies won’t manufacture a vaccine unless there is enough national need. Vaccines have to be safe, effective and saleable. Is the market there for them yet? I haven’t heard of anything on the horizon.”

Lyme disease is difficult to diagnose in horses.

Thomas J. Divers, DVM, Dipl. ACVIM, Dipl. ACVECC, reminds practitioners that horses infected with Borrelia burgdorferi may show a variety of clinical signs, including stiffness in all limbs, hyperesthesia, behavioral changes, muscle wasting over the back, ataxia, skin nodules (pseudolymphoma) or uveitis. More commonly, they may show no obvious clinical signs.

Dr. Divers, a professor of large animal medicine and section chief at Cornell University, says canine vaccines likely will continue to be used on horses because the market may be insufficient for animal health companies to develop and manufacture an equine-labeled vaccine profitably.

Cornell researchers developed an equine vaccine that they used successfully on ponies in 2000 (Vaccine. 1999 Oct 14;18(5-6):540-8), he reports. Some or all of the currently available canine vaccines are likely to be protective in horses because most cause an appropriate antibody response.

A comparison of the antibody response in horses vaccinated with the different canine-approved vaccines has not been published. Although the canine-approved vaccines appear to be safe, based upon veterinarians’ verbal reports, the amount to be injected and the frequency are unproven.

Lastly, many questions remain unanswered regarding Borrelia infection in the horse, including the prevalence and the incidence of clinical disease, and any decision to vaccinate is one to be made by the attending veterinarian and the owner.

“Lyme disease in horses can be an enigma,” Dr. Vaala says. “There are some good tests available that will tell you if the horse has been exposed to Lyme disease and if the antibody titers have changed.”

Vaala notes a growing need for an equine vaccine for the highly contagious pigeon fever, caused by the bacteria Corynebacterium pseudotuberculosis, which is usually found in the soil in warm, arid climates. Also known as dryland distemper, the disease is spread by stable and house flies. Cases have been reported in up to 15 states, from Arkansas to Washington, she says.

Merck has a Coyrnebacterium pseudotuberculosis vaccine for sheep and is looking at adapting its technology for use in equines. Among experts helping with the study is Sharon Spier, DVM, of the University of California, Davis. 

What’s Needed

Vaala also suggests that some vaccines could be improved. She says no vaccine by any manufacturer is labeled to protect against the neurological effects of EHV-1 (equine herpesvirus). She also cites strangles vaccines as not providing long-lasting immunity.

All companies, she says, are working on the next generation of vaccines and, as veterinarians learn more about disease, manufacturers are working to “build a better mouse trap.”

The equine herpesvirus vaccines are hard to develop, Vaala says.

“They have a latent state, viral recrudesence, that makes it tough to protect horses,” she says.

The virus can be reactivated from any stress—showing, shipping, illness.

“A lot of companies’ researchers are looking for ways to improve EHV 1 and 4 vaccines,” Vaala adds.

Don Hoenig, VMD, state veterinarian for Maine’s Department of Agriculture, reinforces that core vaccines are vital. For instance, in his state in 2009, 15 horses, one llama and three pheasant flocks died or were euthanized during an EEE outbreak.

“A vast majority of the horses were not up to date, not vaccinated or had an uncertain history of vaccination,” he says.

Look It Up

A helpful website for equine practitioners, as well as to share with horse owners: www.Outbreak-Alert.com

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