The threat of communicable disease in horses is very real. To name just a few examples, it’s not uncommon to use public water troughs on trail rides or to share one rag to wipe the nose of every horse from one barn before they walk into the show ring.

Though “routine,” each of these practices—and many others—invite the spread of disease, potentially between hundreds of horses.

Though horses are often in the company of others and don’t become ill, what happens when a horse comes down with an infectious disease? How are horse owners alerted, especially if their horse may have been in contact with the sick horse? How do they know what information is real and what has been blown out of proportion? Most importantly, how do owners learn how to keep their horses safe?

These questions and others were the impetus behind the creation of the Equine Disease Communication Center (EDCC). Similar to how the Weather Channel broadcasts weather alerts, the EDCC alerts horse owners to infectious diseases that are reported in North America.

The Cutting Show in Utah

In 2011, a cutting horse show in Ogden, Utah, experienced a significant equine herpesvirus (EHV-1) outbreak. With no means of organized information dissemination, rumors about the situation escalated rapidly, causing a state of near panic in some owners.

In total, over 2,000 horses were potentially exposed to the disease on 242 premises in 19 states. At the outbreak’s conclusion, 90 horses tested positive for the EHV-1 or equine herpesvirus myeloencephalopathy (EHM), another name for the neurologic disease associated with an EHV infection. Fifty-four of the 90 had been at the Ogden event. Thirteen horses died or were euthanized.

During the outbreak, Facebook and X (then called Twitter) lit up with rumors, causing heightened anxiety over horse health and spurring the cancellation of equine events across the country, even though most events had no connection with any horses that attended the Ogden event.

Seventeen of the confirmed EHV-1 and EHM cases were in California; show organizers opted to cancel 142 of the 530 sanctioned shows that were to be held in the state that year. The economic impact of those cancellations was significant and would be felt for years.

Creating the Equine Disease Communications Center

It became clear that a unified industry response plan to disease outbreaks was needed—one that not only allowed for the dissemination of legitimate data, but that also provided vetted information on how to prevent disease transmission and how to handle disease outbreaks.

The American Horse Council, the American Association of Equine Practitioners (AAEP), and the United States Equestrian Federation (USEF) all collaborated to fundraise and launch the Equine Disease Communications Center, which went live in 2015.

Nathaniel “Nat” White, DVM, DACVS, professor emeritus of equine surgery at the Marion duPont Scott Equine Medical Center in Leesburg, Va., and director of the EDCC, organized the working model and gave the EDCC its moniker. In 2023, White won the Equine Industry Vision Award for this work at the American Horse Publications Equine Media Conference in Tempe, Ariz.

According to White, it was anything but a one-man show. State veterinarians, veterinary practices, horse-owner organizations (like breed and discipline associations), and individual donors helped—and continue to do so.

“Similar to the CDC [Centers for Disease Control and Prevention], the EDCC seeks information about disease outbreaks, posts messages, and informs the equine industry about confirmed diseases, their location, and if there are potential risks to other horses,” White explains.

How It Works

Unlike a phone number or website where anyone can submit leads on suspected illness, the EDCC allows only specific people to report disease: an attending veterinarian or a state or federal official.

The veterinarian or official submits a confirmed or suspected disease through the EDCC website, which records the information in the database. The database then generates an alert, which is posted to the EDCC website and Facebook page.

Anyone who has become an alert subscriber via the EDCC website is also emailed. The reported disease is linked to an EDCC disease page, which has information describing the disease, the diagnosis and the treatment, says White. Downloadable disease fact sheets are also available.

All information regarding disease outbreak mitigation and how to handle an affected horse is reviewed for accuracy by the AAEP Infectious Disease Committee, which is populated by subject matter experts.

Reportable Diseases

Though the veterinarian or official can report a confirmed case of any equine disease to the EDCC, reporting of infectious diseases is of the most importance, says Katie Flynn, BVMS, the U.S. Equestrian Federation’s senior staff veterinarian. A confirmed “reportable” disease is submitted to the EDCC by the state veterinarian, who is made aware of a confirmed diagnosis by the testing laboratory.

A reportable disease is one that is deemed to have a potential for significant impact on the equine industry, both on the health of the United States equine population and economically. When a reportable disease is diagnosed, the veterinarian or laboratory employee is required to report the disease to state or national veterinary health officials.

The list of reportable disease varies by state and may include:

◆ Equine Herpesvirus-1 neurologic (Equine Herpesvirus Myeloencephalopathy)

◆ Equine Herpesvirus -1 abortion

◆ Equine influenza, Streptococcus equi (strangles)

◆ Western Equine Encephalitis (WEE) and Eastern Equine Encephalitis (EEE)

◆ West Nile virus (WNV)

◆ Equine infectious anemia (EIA)

◆ Equine piroplasmosis (EP)

◆ Equine viral arteritis (EVA)

◆ Rabies

◆ Vesicular stomatitis (VS)

Many veterinarians, state horse councils and other horse-health organizations rely on the EDCC to inform horse owners of disease outbreaks. The alerts are posted in real time—the same day they are reported.

However, this doesn’t mean that the alert comes out the day the horse becomes ill; the alert is posted the day the veterinarian receives positive confirmation that the horse is ill with a specific disease.

The alert system can provide information about disease risk to horses at a specific location or at the location where the horses intend to travel, like to a horse show or trail ride.

“As the Equine Health and Biosecurity Veterinarian for the USEF, I encourage all horse show managers to visit this site frequently to keep informed of disease occurrences in the area,” says Flynn. “[This way] they can be prepared to implement stricter biosecurity measures, such as requiring shorter-dated health certificates or mandating temperature-taking for horses at their event.”

The EDCC alert system isn’t just for equine event managers or those who travel with their horses.

“This is also a beneficial tool for boarding facility managers,” says Flynn. “If a disease is detected in the geographic area of their facility, they can implement enhanced biosecurity measures, such as requiring every horse to have its temperature taken twice daily to quickly identify and isolate any potential sick horses to protect the rest of the herd.”

But Is It Working?

Though the EDCC is working as intended (as a warning system that can help prevent the spread of infectious equine diseases), more reporting of diseases is necessary. Submission of any disease to the EDCC is voluntary—whether it’s considered reportable or not.

“Reporting to the EDCC is voluntary, but strongly encouraged as a means for increasing awareness of equine infection diseases in the U.S.,” says Flynn. “Horse owners want to know if there is disease in the area that could put their horse at risk, so it’s important for horse owners to support and encourage reporting of equine infectious diseases cases by their veterinarian to the EDCC.”

The EDCC is a unique resource that serves to protect horses and the horse industry. All horse owners should sign up for EDCC alerts so they can be informed and aware of possible infectious disease in their area.

“Vigilance is necessary to ensure we’re adequately prepared for the storm—horse health, weather, or otherwise,” says White.

You can do your part by promoting the EDCC “as the trusted, accurate and verified disease alerts and biosecurity information,” says Flynn.

There is no fee associated with the use of the EDCC. However, donations to keep the service going are welcomed—and necessary.

Learn more at equinediseasecc.org.

This article about the Equine Disease Communications Center appeared in the September 2024 issue of Horse Illustrated magazine. Click here to subscribe!

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Here’s what to watch for to catch this cancer early and what to do if your horse has it.

What is Squamous Cell Carcinoma?

The name itself—squamous cell carcinoma—can sound confusing and even intimidating, so let’s start with the basics.

What is a squamous cell, anyway? These are normal cells in the body. They are primarily found in the skin, particularly at mucocutaneous borders. These borders are where dry skin intersects with a mucous membrane, such as the line between skin and the lips, nostrils, anus, genitals, and eyelids.

Understanding the normal location of this cell type then provides context for where SCC is commonly found: in or around the eye, the genitalia and anus, and lips/nose.

The term “carcinoma” refers to a type of cancer that starts within skin cells or the lining of internal organs. In addition to SCC, there are a few other types of carcinomas, such as basal cell carcinoma, which is rare in horses but common in humans.

SCC development is related to sun and subsequent UV exposure. It’s no surprise, then, that SCC is common in horses who can spend most of their life outside, accumulating UV skin damage.

However, horses with lots of non-pigmented (pink) skin on their faces, such as horses with wide blazes or bald faces where eyes and muzzles have pink skin, have a higher rate of SCC.

Breeds that tend to have extended white on their faces such as Clydesdales, Belgians, Appaloosas, and some Paints have a higher risk of developing SCC than other breeds. Lighter-colored horses, such as palominos and cremellos, are also at higher risk for SCC.

What To Look For

So what does SCC look like in a horse? Typically, this tumor initially appears as a small, raised lump or nodule under the skin. SCC within the eye may give the cornea a flat or roughened opaque appearance.

Early SCC can be easily missed due to its small size and sometimes hidden location. As the tumor grows, it can erupt, become ulcerated, and start to impinge on neighboring tissues. SCC of the eyelid can be particularly problematic. As the tumor enlarges, it may start to pull at the lid. This can either rub the cornea or pull outward, resulting in the inability of the horse to fully close his eye.

Because it is easier to remove when it is small, the best course of action with SCC is early detection. When you groom your horse, keep an eye out for odd bumps or lesions. Owners of white-faced horses should be especially observant of their horse’s facial features on a regular basis, including a close look at the eye itself.

SCC on the eyelid typically starts off looking like a small scab, while SCC at the corner of the eye or within the third eyelid is typically a raised, pink mass. Horses with ocular SCC may also have eye discharge.

Regular checks should also include the genitals and underneath your horse’s tail. For male horses, make the most of sheath cleaning: this is the perfect time for an inspection.

SCC Treatment Options for Horses

What should you do if you find something suspicious on your horse? The first step is to have your vet out. Although you may have a very high suspicion of SCC based on the lump’s location or your horse’s history or pigment pattern, you can’t diagnose SCC based on visual examination alone.

Sometimes SCC can be confused with scar tissue, other types of tumors (such as papillomas or sarcoids), or even a skin allergy. A biopsy, or tissue sample, is the best way to definitively diagnose this tumor.

Once your vet confirms the diagnosis, it’s time to talk treatment options. As with most tumors, its location, size, and involvement of neighboring tissues heavily influence treatment options and prognosis.

Surgical removal is a common choice, but location of the tumor dictates treatment success rate. For example, SCC at the corner of the eyelid can be very challenging to reconstruct after removal of the diseased tissue. Other times, SCC may grow into deeper structures around the eye. In these circumstances, total enucleation may be the best option for the horse’s future.

Adjunct treatments along with surgical removal are the most common choices of treatment and management of SCC. These adjunct therapies occur at the time of surgery and may need to be repeated.

Cryotherapy (freezing) is a common adjunct therapy that can be done on site at your barn. Your vet will apply liquid nitrogen, which is -320° Fahrenheit, to the edges where the tumor was removed. This helps destroy any leftover cancer cells.

Some radiation and chemotherapy options are also available. Depending on the regimen, they may require a visit or two to a referral hospital for application.

Photodynamic dye therapy (PDT) is a relatively newer option for SCC treatment. This therapy involves injecting a dye containing photosensitive compounds into the affected area.

This dye is taken up selectively by the cancer cells. Next, a focused beam of light using a specific wavelength is directed at the diseased tissue. The light reacts with the dye, creating a skin reaction that kills the tissue.

Because only the cancer cells take up the dye, other nearby healthy tissue is relatively unaffected, providing a much more focused treatment compared to radiation and chemotherapy.

Prognosis after surgery and adjunct therapy for SCC depends heavily on the size and location of the tumor and how locally invasive it is. Horse owners should note, too, that once a horse has had SCC, he is at higher risk of developing it again.

Prevention Tips

Along with regular close monitoring of your horse’s skin, reducing your horse’s exposure to UV radiation is another tool for SCC prevention. Regularly applying sunblock to your horse’s non-pigmented facial features can help, as can putting a fly mask on your horse in the summer months to shade his eyes.

Interestingly, researchers at the University of California-Davis School of Veterinary Medicine have identified an equine gene variant that is a risk factor for ocular SCC in certain breeds, including Haflingers, Belgians, Rocky Mountain Horses, Connemaras, Holsteiners, and Belgian Warmbloods.

Horse owners can send plucked hairs from the mane that include the roots to the UC Davis Veterinary Genetics Laboratory to identify whether their horses are at higher genetic risk of developing ocular SCC.

Treatment options continue to develop for this equine cancer, and horse owners have more options than they did just a decade ago. While this is encouraging, the best course of action is still vigilance to catch this tumor early for a full recovery.

Key Takeaway

As with any cancer, squamous cell carcinoma is intimidating. But remember—prevention and early detection are your best weapons.

This article about squamous cell carcinoma in horses appeared in the June 2024 issue of Horse Illustrated magazine. Click here to subscribe!

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What is Botulism in Horses?

A disease caused by a neurotoxin released from Clostridium botulinum bacteria, botulism neurotoxin is one of the most lethal natural substances. Botulism attacks the nervous system of infected mammals, binding to nerves and impairing their function. In extreme cases, the cardiac and respiratory systems can be affected, rending the animal unable to breathe or maintain a regular cardiac rhythm.

Though there are seven types of botulism—A, B, Ca, Cb, D, E, F and G—the one of most concern to horse health is type B, which causes more than 80 percent of equine botulism cases.

Botulism is a naturally occurring toxin found in the environment that is harmful to mammals.

“Horses are exquisitely sensitive to botulism,” says Rachel Blakey, VMD, of Maryland Equine Center in Reisterstown, Md. “The amount of botulism that can kill a horse may not impair a mouse; horses are simply that susceptible.”

Botulism bacteria are very hardy and live without oxygen and sunlight. They can be found in the soil, in the sediment of lakes and streams, and in the intestinal tracts of mammals.

How Botulism is Transmitted in Horses

A horse can get botulism in three ways, though ingestion of the preformed bacteria is the most common.

1. By eating hay or feed that has botulism toxin already in it (ingestion of preformed bacteria). This is the means most often associated with feed-based poisonings, like the contaminated alfalfa cubes that killed 45 horses in late 2022.

Animals that are accidentally baled into hay can release the toxin from their intestinal tract when they begin to decay, contaminating the hay that surrounds them. Large round bales are particularly susceptible to botulism contamination because their mass allows for more room for contamination than small square bales.

2. By ingesting feed, hay or other organic matter that contain botulism bacteria, which then multiply in the intestinal tract and release neurotoxins (transmission in this manner is most common in foals).

Botulism bacteria favors dark, moist environments, like piles of wet feed or tree roots that aren’t exposed to sunlight. In these environmental conditions, botulism is not accessible. However, when a tree falls over and a horse chews on the roots or when the pile of feed is discovered and ingested, the bacteria can become harmful as it multiplies in the intestinal tract and releases the neurotoxin.

Botulism in foals is also called “shaker foal syndrome” or “barker foal syndrome,” as the foal’s vocal cords are paralyzed, making them sound as if they’re barking when they vocalize.

3. By the introduction of bacteria through wounds. Wounds that encapsulate bacteria while healing provide an anaerobic environment where the bacteria flourish.

It’s important to note that botulism is not a disease that spreads between horses. If one horse on the property gets botulism, he is not “contagious”; in other words, he cannot give botulism to other horses via nasal secretions, shared tack, or in any of the other ways equine viral diseases spread.

Clinical Signs of Botulism

The extent to which a horse is affected by the botulism toxin depends on how much they have ingested, says Blakey. No matter if the illness comes on rapidly or more gradually, the initial symptom is always the same: muscle weakness.

The first muscles in horses that lose tone (meaning they are not able to hold themselves as needed to function properly) include the eyelids, tongue, tail and anus. This means that a horse with botulism will have problems eating, chewing and swallowing, and his muscles will fatigue quickly; he may drool or have upper eyelids that droop.

A horse with botulism will also experience muscle tremors. Progressive paralysis occurs in more severe cases, often affecting the horse’s ability to stand; it can also affect a horse’s respiratory and cardiac systems, causing death.

The biggest predictor of whether a horse will survive a bout of botulism is if he can stand.

“If a horse can stay up, they often survive,” says Blakey. “Sixty percent of horses that go down, but can rise, survive.” A horse that is recumbent and unable to rise without assistance has a poorer prognosis.

So how does a vet determine if a horse has botulism and not another issue with similar clinical signs, such as equine protozoal myeloencephalitis (EPM)?

“The very first thing I ask when I see any signs like this is, ‘Is your horse vaccinated against botulism?’” says Blakey. Knowing if a horse has been vaccinated against botulism allows her to immediately rule out botulism as the cause of illness, saving time (and money!) while drilling down to a diagnosis.

Time is of the essence in botulism treatment, but treatment can be delayed as horse owners and veterinarians work to determine exactly what is happening with the horse’s health. Some horses may lie down more as their muscles fatigue, which can be misdiagnosed as colic, says Blakey.

One telltale sign that the horse has botulism and not another disease is that the muscle weakness the horse is experiencing is symmetrical, says Blakey. Horses with botulism have flaccid, floppy muscles, while horses with tetanus have hard, rigid muscles.

Additionally, one of the biggest things to rule out is trauma, says Blakey.

Treatment and Prevention

Early recognition and prompt treatment is imperative in giving a horse the best chance at a full recovery. If botulism toxicity is suspected, the horse can be treated with plasma containing an antitoxin, which binds to free toxin molecules in the blood, preventing them from attaching to nerve cells. This treatment is not cheap (often running between $1,500 and $3,000), and the antitoxin cannot reverse the effects of the toxin that has already bound to nerve cells.

Eventually the toxin degrades, however. If the horse survives, all muscular deficits he experienced while the disease was active will fade; botulism has no lasting effects on a horse. However, muscling and physical aptitude may take weeks or months to return to normal as new nerve endings grow.

The best preventative measure for ensuring a horse doesn’t contract botulism? Vaccination.

“The botulism vaccine is very effective,” says Blakey. “I insist all my broodmares be vaccinated, so I haven’t seen a shaker [foal] in years,” says Blakey. “And I encourage everyone to vaccinate for botulism. The cost of the vaccine is a pittance compared to the cost of antitoxin treatment for affected horses. I also push hard for those who feed round bales to vaccinate their horses again.”

There is no downside to botulism vaccination and there is not a population of horses that could not benefit from the protection. While there is a chance that the horse may become sore around the injection site (as with any vaccination), the minor soreness is a minimal price to pay for the safeguard from the toxin the vaccination provides.

Are Vaccinations Effective for Everything? There are multiple types of botulism that can affect horses, including types A, B and C, though type A is uncommon. Equine botulism vaccines are effective against type B, but don’t provide protection against the other types. Though a botulism vaccine is not considered a “core vaccine” by the American Association of Equine Practitioners (meaning these vaccines should be given to every horse, no matter where they reside), there are specific populations of horses that should be vaccinated against the disease: ◆ Broodmares ◆ Horses that live in areas of the United States where botulism is endemic: The disease is most prevalent in California, Kentucky, Maryland, Ohio, Pennsylvania and Tennessee, though it can occur in any state. ◆ Horses that eat from round bales Botulism vaccination begins with three doses given at four-week intervals, with boosters given annually. After the initial series, pregnant mares should be vaccinated yearly (two to four weeks before foaling). Foals in high-risk situations can start the series of botulism vaccines as early as two weeks old. Foals born to unvaccinated mares or those that have not ingested enough quality colostrum from the mare (failure of passive transfer) can have botulism vaccination initiated early in life. Botulism protection provided by the mare’s colostrum generally wanes by about 5 months of age, and vaccination should be considered at this time.

Key Takeaway

“Botulism is a normal part of our environment,” says Blakey. “It’s not some weird threat, and it doesn’t happen because a horse owner isn’t ‘clean.’”

However, like many other equine-related health concerns, good husbandry can minimize the incidence of disease. This includes not feeding moldy hay or grain or hay that has been baled with a high moisture content, plus keeping pastures and barns free from dead rodents and animals.

If horses live in an area where botulism occurs or if they’re fed round bales, vaccination is the most-recommended route of prevention.

This article about botulism in horses appeared in the March 2024 issue of Horse Illustrated magazine. Click here to subscribe!

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What is Vesicular Stomatitis?

Vesicular stomatitis (VS) is a viral disease that primarily affects horses and cattle, though it can also affect pigs, sheep, goats, llamas and alpacas. It’s not a new disease; it’s been referenced in texts as far back as the mid-1800s.

VS is found only in the Western Hemisphere; it’s considered an endemic disease of the Americas, occurring in the warmer regions of North, Central and South America. Even though it’s old, there is no vaccination that can protect horses from contracting the disease.

Horses affected by VS may have a fever or salivate excessively and go off their feed. However, the most tell-tale sign of the disease is blister-like lesions (vesicles) on areas of the horse’s body that have minimal hair, like around the mouth, nostrils, coronary bands, sheath or teats.

Blisters can also form in the mouth and on the tongue. When these blisters break, they leave behind raw, exposed, painful skin. Horses with VS will often be reluctant to eat or move.

Age or Underlying Conditions

While often quite painful, most horses heal in a few weeks with nothing more than supportive care, which can include the administration of non-steroidal anti-inflammatories to treat pain.

However, older horses or those with an underlying condition may have a more difficult time recovering from a VS infection; these are the horses Pelzel-McCluskey is particularly concerned about.

For these horses, she recommends conferring with the horse’s treating veterinarian about the possibility of feeding a beet pulp instead of hay or grain, or considering the administration of intravenous fluids. Oral lesions can cause enough pain to stop a horse from eating or drinking enough to keep him healthy, putting him at risk of dehydration or colic.

Even horses that become significantly lame from lesions on their coronet bands often heal with no complications other than a defect demarcation in the hoof wall when it grows out.

Why Is Vesicular Stomatitis Concerning?

It’s been established that VS isn’t particularly deadly, and it’s only found in a small geographic area relative to the size of the world.

Why then, is it a disease horse owners need to worry about? Because the impact on the economy—both within the United States and abroad—can be substantial. VS is an international trade issue, explains Pelzel-McCluskey.

The lesions common in VS infections look disturbingly similar to the lesions caused by foot-and-mouth disease (FMD), which can affect sheep, goats, pigs and cows (FMD does not affect horses, cats or dogs). FMD spreads rapidly, and just one case can shut down international trade completely and have massive economic consequences. FMD is one of the most-feared livestock diseases: In some countries, a FMD diagnosis carries a slaughter mandate.

This means that livestock owners in countries where animals can contract FMD (which doesn’t include the United States; FMD was eradicated here in 1929) will do anything it takes to not have animals present with something that even looks like the dreaded disease—which includes VS.

Mandatory Reporting

Like most things in life, open lines of communication are key. All VS cases are “reportable,” meaning that a veterinarian is required to report suspected cases to state and federal animal health officials, who then have to notify trade partners if cases are confirmed.

To ensure that international trade of livestock continues (even if there is a VS outbreak), the U.S. agrees to quarantine all horses affected by VS and report all VS situations to countries with which they trade. If these pieces are in place, equine trade can continue even in the face of an outbreak.

If these things are not adhered to, however, international trade can come to an immediate halt. This causes huge economic impacts, as horses cannot be imported or exported for showing, racing or sales. Shipping of frozen or cooled semen can continue, though some countries may require a stallion test negative before the semen will be accepted for importation.

While there are no exact figures available, it’s estimated that 30,000 horse are shipped by air each year, the majority internationally. So, while you personally might not be sending your horse to an overseas competition, you may have contact with someone who will be around horses that plan to travel abroad—and they may unintentionally spread the disease.

How Vesicular Stomatitis is Transmitted

There are three main VS insect vectors: black flies, sand flies and biting midges, explains Pelzel-McCluskey.

“Both the black flies and the Culicoides [midges] drive most of the VS outbreaks in the United States, though there may be some other insects that can spread the disease as well,” she says.

Interestingly, if a VS-carrying insect bites a horse where he has hair, the horse will not develop the outward lesions associated with VS, but he will create antibodies to the virus. The lesions develop only if an infected insect bites a horse where he has little hair cover.

While this seems like the stars must align for the disease to spread, it can also be transmitted from horse to horse via direct contact or on items that have had contact with the ruptured lesions of an infected animal, like buckets, shared troughs and feed bins; even eating out of the same round bale or sharing communal salt blocks can spread the disease, says Pelzel-McCluskey.

Stopping the Spread

VS can spread rapidly, so quarantining affected horses is imperative. The virus can remain active for seven to 10 days once lesions appear on the horse; quarantine lasts for “14 days from the onset of lesions in the last infected animal on the premise.”

Local geography affects how VS vectors move and lay their eggs: black flies like flowing water, while Culicoides prefer damp, muddy areas like those around water troughs and riverbanks.

Black flies’ preference for moving water explains how infected insects can often end up miles from original outbreaks. VS most often enters the United States from Mexico.

“We have a series of historically expected cases because of the way water moves,” explains Pelzel-McCluskey. “It’s often seen in the Southwestern United States and the Rocky Mountain area.”

While it would be expected for VS to appear only in the late spring and summer when biting insects are at their peak, it’s not unusual to have VS outbreaks in the dead of winter in Colorado or Wyoming, according to Pelzel-McCluskey.

These outbreaks are almost always the result of Culicoides, which can withstand cooler weather than black flies. These insects become inactive in cold weather, but one warm day—even in the dead of winter—can reinvigorate them. Culicoides lay their eggs in wet areas, like around water troughs and on riverbanks, the very places livestock go when the weather warms.

Additional Prevention Tips Keep bedding dry Feed horses in individual feeders Clean and disinfect horse trailers, equipment, waterers and other equine equipment regularly Eliminate muddy areas in fields and on ground Keep manure piles as far as possible from fields and stables Investigate the use of parasitic wasps or guinea hens to keep insect populations in check

How to Handle an Outbreak

Controlling a VS outbreak must be a multi-pronged approach, says Pelzel-McCluskey.

• First, the owner must isolate a VS-infected animal to minimize disease spread in the horse’s home herd. Additionally, the farm itself must be quarantined to limit the movement of possibly infected animals.
• Second, an aggressive vector control program to reduce the fly population must begin.
  “Owners need to remove manure and standing water,” says Pelzel-McCluskey. “They also need to get rid of tall weeds where insects tend to hide.”
• Third, fly-control measures need to be implemented or ramped up. This includes daily application of fly spray to horses (including all particularly vulnerable areas like under the belly, sheath or teats and on the face) and the implementation of tools like parasitic wasps that feed on fly larvae, fans (to keep air flowing), or equine fly gear.If you choose to use things like fly sheets, fly masks or fly boots, it’s critical that they cover areas that are most at risk, including muzzles (think fly masks with nose coverings), bellies (fly sheets with bellybands may help) or ears (fly masks with ear coverings).

“Think hard about biosecurity and vector mitigation for disease reasons,” says Pelzel-McCluskey. Both play a part in halting the spread of VS. “The horse doesn’t need to be living in a screened stall,” she clarifies. “We have so many infectious diseases that can be prevented by good biosecurity practices and vector control. No one can do it all, but you do want to have a [fly-control] program in place.”

Additionally, owners who implement new fly-control measures should keep a close eye on whether those measures are working. If they are not working at all or don’t seem to be working well, consider trying another, says Pelzel-McCluskey.

Key Takeaway

Pelzel-McCluskey advises horse owners and caretakers to take vesicular stomatitis seriously.

“It’s not just your individual horse that is affected by the disease,” she says. “Good care means you’re improving the lives of all horses on the property,” which has a ripple effect into the entire population of horses worldwide.

This article about vesicular stomatitis appeared in the January/February 2024 issue of Horse Illustrated magazine. Click here to subscribe!

The post An Overview of Vesicular Stomatitis appeared first on Horse Illustrated Magazine.

Discover the transmission, progression, treatment and possible complications of one of the oldest equine diseases in the world.

An Age-Old Disease

“Strangles was one of the first equine diseases to be described in 1251,” says Katie Flynn, BVMS, Senior Staff Veterinarian-Equine Health & Biosecurity for the United States Equestrian Federation and former Kentucky State Veterinarian.

Though nearly 775 years have passed, it still affects equines globally and remains one of the most diagnosed equine diseases in the world.

“In the United States, strangles is considered endemic, meaning it’s detected regularly in the horse population,” says Flynn.

If you’ve ever had strep throat, you can commiserate with a horse that has strangles; both infections cause enlarged lymph nodes in the head and neck. Strangles can affect horses of any breed or age, but older horses typically show more mild signs.

How Strangles Is Transmitted Among Horses

The Streptococcus equi bacteria that cause strangles are primarily transmitted through nose-to-nose contact with another horse, but the bacteria can also be transferred through feed, water, buckets, stall walls, veterinary instruments, clothes, grooming and barn tools, tack, and trailers.

Nearly any surface can harbor S. equi for a time, which is why strict biosecurity protocols for ill horses are imperative.

“Whatever you touch has the potential to be contaminated, and if not cleaned and disinfected, can transfer the bacteria to a new horse directly or via someone else’s hand to a new horse,” says Flynn.

Before panic ensues, it’s important to understand that S. equi can stay active in water buckets and moist areas for four to six weeks, but the bacteria can only survive for about one to three days in drier areas such as on fencing or in soil, says Flynn.

“Because the organism typically dies quickly in a sunny, dry environment, the usual source of infection is an infected horse,” she explains.

Similar to tracing the transmission of Covid-19, determining when exactly a horse got sick—and from whom—can be nearly impossible. The time between a horse’s exposure to the bacteria and the onset of clinical signs can be anywhere from three to 14 days, says Flynn.

Progression of Strangles in Horses

Though most horse owners associate a snotty nose as the first indication that a horse may have strangles (or another bacterial or viral disease), the first sign that something is amiss can actually occur 24 to 48 hours before in the form of a raised temperature.

If the fever is caught before a horse develops a snotty nose, a strangles outbreak can be minimized if that horse is immediately isolated from all other horses. It’s important to remember that an elevated temperature is when it goes up from that particular horse’s baseline, and not solely when the temp rises above the standard 101 degrees Fahrenheit.

“If there’s a jump, even if it’s still within the ‘normal’ range, the horse should be moved to an isolation area,” says Ashley Boyle, DVM, DACVIM, associate professor at the University of Pennsylvania’s School of Veterinary Medicine New Bolton Center.

As the disease progresses, so too will the horse’s clinical signs; his temperature will rise, often alarmingly. Thick, yellow nasal discharge is often seen, and the horse may have swollen lymph nodes under his jaw and around his throat latch.

“When the infection involves lymph nodes above the airway, horses adopt an extended neck posture and may cough,” says Flynn. Other signs of illness can include poor appetite, foul-smelling breath, lethargy and loss of condition.

A vet caring for a horse that is suspected of having strangles will perform a nasopharyngeal swab or a nasopharyngeal wash on the horse. The nasopharyngeal swab is extremely similar to a Covid test: A piece of cotton is passed up the nose, rubbed around the nasal passages, and sent for testing. A nasal wash is like a neti pot for horses; the vet will run a thin tube up the horse’s nose, flush sterile saline into the tube and catch what runs out the other nostril. This fluid is then tested. 

A polymerase chain reaction (PCR) test is the test most used to detect strangles; it detects S. equi bacterial DNA. Culturing the secretions is also a possibility, though this is not as rapid or as sensitive a form of testing.

Some vets will perform a blood test to measure serum antibody levels, but this test is not useful in detecting current infection.

“However, paired serum samples taken two weeks apart can be useful in recognizing recent exposure,” says Flynn.

Treatment of Strangles

There is not much that can be done for a horse with strangles except supportive care while the infection runs its course.

This may involve administering anti-inflammatories to lower body temperature or feeding the horse wet feed or hay from the ground. Feeding in this manner will make the food easier for the horse to swallow, as well as encourage abscesses to drain. A hot compress placed on abscesses can encourage them to burst.

Some vets administer antibiotics to strangles-exposed horses as soon as they have an elevated temperature to prevent abscess formation. This practice is controversial, as the antibiotics may allow the horse to be re-infected with strangles the next time he is exposed.

Strangles bacteria can hide in a horse’s guttural pouches, which are sacs of air located on either side of the horse’s head. These pouches are designed to cool the brain, ensuring that the blood near the brain is below the horse’s core body temperature, especially during exercise.

A horse with strangles will need to have his guttural pouches scoped before he is considered free from the disease. Scoping involves threading a long, flexible rod with a camera up through the horse’s nose and examining the pouches. This flexible rod can also be used to administer antibiotics into the pouches if strangles bacteria is discovered.

A small basket can also be placed on the end of the rod to remove chondroids (dried pus) that may be found in the guttural pouches. A horse must be free of bacteria and chondroids, as well as have multiple negative nasal washes or nasal swabs, to be considered “clear” from the disease.

Strangles Vaccine There are two types of strangles vaccines available: intramuscular (IM) injection, which is given like a traditional vaccine, and intranasal, which is misted up the nasal passage and provides mucosal protection, as well. It’s important to remember that vaccine administration does not mean the horse will not get sick; it simply means that the horse will have less-severe disease presentation. “I do not recommend that every horse get the strangles vaccine,” said Boyle. The vaccine is really only needed by competition or trail horses that are regularly exposed to unfamiliar horses or for horses that live with horses that regularly travel, she notes. Horses that have been exposed to a strangles outbreak should wait at least one year before they’re vaccinated with either the intranasal or intramuscular vaccine. Some horse’s immune systems can be overstimulated by the vaccine and the animal might develop purpura, says Boyle. Purpura hemorrhagica is swelling of the blood vessels in the head, neck and abdomen. Most cases are mild and are treated with antibiotics and corticosteroids. It’s important that horse owners understand that vaccination alone is not effective, says Katie Flynn, BVMS, Senior Staff Veterinarian-Equine Health & Biosecurity for the U.S. Equestrian Federation. “Vaccination may be an effective method of disease control in individual [horses] and herds when used in conjunction with a biosecurity plan.”

Complications

“Equine strangles is a disease with a high morbidity rate, meaning many horses on a premises may become ill with the disease,” explains Flynn. “But approximately 98 percent of horses recover after several weeks in the acute phase of disease. Death due to strangles is not common.

“Inflammation associated with lymph node abscess formation and rupture may cause obstruction of the upper respiratory tract, hence the name strangles,” she adds. Damage to the nerves near the abscess may result in the horse having difficulty breathing; further damage can make it difficult for the horse to eat.

One of the scariest complications of strangles is its bastardization, where abscesses may occur in multiple sites, including the brain, abdomen and mammary glands. Additionally, cases of S. equi pneumonia have been known to occur.

Should Anyone Be Notified If Your Horse Has Strangles?

Strangles is considered a “reportable” disease in most states, meaning that the state veterinarian must be made aware of a positive test result (this is the responsibility of the testing laboratory or the veterinarian, not the horse owner).

From there, the disease is classified as either “reportable actionable” or “reportable monitored,” according to Flynn.

“In the majority of states, strangles is ‘reportable monitored,’ meaning no regulatory action is taken by state officials, but they do monitor the detections to determine if there is an increase or decrease in prevalence or a change in geographic distribution,” she says. “Very few states take regulatory action such as quarantine, testing and required biosecurity measures.”

There are multiple reasons why strangles may not be “reportable actionable” in a state. This can range from lack of state regulatory resources to do things like implement quarantine, the challenges associated with releasing a quarantine (and the testing that must take place to do so) or the state’s equine industry may not have requested or does not support enforceable action for the disease, says Flynn.

The fact that the disease is not deemed “actionable” in many states should not in any way indicate that the disease is not serious, says Flynn.

“Strangles can pose significant risk to the individual equine, the herd, and the national equine population if proper biosecurity protocols are not followed.”

Containing an Outbreak

There are three keys to containing a strangles outbreak, says Boyle. These are taking temperatures, isolating and separating.

The ability to detect a sick horse by any deviation from his “normal” temperature will give farm owners 24- to 48-hour advance notice that the horse may have strangles. Once the horse is identified, if he’s immediately moved (isolated) and separated from not only his neighbors, but also from staff who may interact with multiple horses, the likelihood of minimal farm impact increases.

The isolation area need not be fancy, Boyle stresses—it just needs to be effective.

“Even if it’s a shed that’s got a gate to separate them, it’s better than nothing,” she says. “Even better would be to have a paddock as a barrier in between affected and unaffected horses.

“I deal with farms all the time that say, ‘Well, everyone is exposed because I had one horse test positive,’” says Boyle. “This truly isn’t the case. Every horse may be minimally exposed, but I have successfully minimized outbreaks by immediately isolating the horse. The ‘everyone is exposed’ mentality is not the way to go—you’ll deal with a much longer outbreak and have more horses with complications that may also turn into potential carriers afterward. What you do up front [to isolate and separate] can really limit the outbreak.”

In addition to being proactive about isolating horses that are sick or that may become sick, all other traditional biosecurity measures should be in place: not sharing buckets, tack or equipment; handling the ill horse last (and preferably by just one staff member), and paying scrupulous attention to details like ensuring hose ends aren’t dipped from bucket to bucket.

Key Takeaway

Though not often deadly, strangles presents a unique set of issues related to the ease with which it’s transmitted and the delay in symptom onset. Keen attention should be paid to all horses that travel off the farm and daily temperature-taking should be incorporated into every horse’s daily health check.

This article about strangles appeared in the November/December 2023 issue of Horse Illustrated magazine. Click here to subscribe!

The post An Overview of Strangles in Horses appeared first on Horse Illustrated Magazine.

A: Horses do very well in cold temperatures, provided they are used to them and have a good winter coat, good teeth, enough body fat, and enough hay to eat. A horse that has poor teeth, is body clipped, older, thin, or has recently moved from a warmer climate will probably need to be blanketed and given extra grain and concentrates. If your horse is shivering or losing weight in the winter, he’s too cold!

In cold temperatures, it’s very important that your horse has an adequate supply of good-quality hay. A healthy, average-sized horse will need about 20 pounds of hay a day in spring and summer. In the winter, he might need up to 40 pounds a day.

If you blanket your horse, make a habit of running your hands over his body to check his weight. It can be hard to tell if your horse might be losing weight without touching him every day. Remember that horses generate body heat by fermenting their feed in their large intestine. Empty bellies equal cold horses. There’s a reason they’re called “hay burners!”

This article originally appeared in the January/February 2017 issue of Young Rider magazine. Click here to subscribe!

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Breathe in, breathe out. Simple enough, right? Hardly, as anyone with a cold, allergies or asthma knows. Now think about our horses. Weathering winter in stuffy barns, working in dusty indoor arenas … a horse’s respiratory system, particularly during the colder months, can be easily stressed. Here’s what to watch for when it comes to your horse’s breathing and how to stay on top of his respiratory health.

RAO by Any Other Name

One of the most common respiratory ailments diagnosed in horses is recurrent airway obstruction, often abbreviated RAO, or referred to by its common name: heaves.

A much older, colloquial term you may have heard for this condition is “broken wind.” In decades past, when the physiology of this equine disease wasn’t fully understood, it was known as equine COPD, or chronic obstructive pulmonary disorder.

However, as researchers learned more about the cause, they discovered the equine condition was very different from the human respiratory disease with the same name. In order to avoid confusion (and more accurately describe the equine disease), the name was changed to RAO.

Causes and Effects

In the broadest sense, RAO is an allergic reaction to inhaled allergens, most commonly airborne microscopic molds and pollens. Some veterinarians refer to this condition as “equine asthma.” With no age, gender, or breed predilection, RAO can occur seemingly at random—it all depends on your horse’s individual response to allergens in the air.

In an affected horse, his immune system will occasionally overreact to an inhaled allergen. This overreaction occurs deep in the airways where special immune cells panic, releasing chemicals that cause a range of clinical signs, starting with airway constriction.

As airways become smaller, the horse has to breathe harder to get the same amount of air. This results in the classic “heavey” horse: flared nostrils, elbows sometimes out, and abdomen heavily moving with every breath.

With severe and unmanaged heaves, this intensified breathing results in stronger than usual abdominal muscles. These overdeveloped abs look like a line running slightly above the ventral aspect of the horse’ s abdomen from flank to chest. This is called a “heave line.”

Diagnosis

Most veterinarians will be able to diagnose heaves based on a horse’s history and clinical signs alone. If there is any ambiguity, however, fluid samples from your horse’s airways can be collected, cultured for bacterial growth, and examined under a microscope. Depending on the types of cells collected, a diagnosis can be made regarding your horse’s respiratory health.

Horses with heaves will typically have an increased respiratory rate and effort while at rest—this is a direct result of the airway constriction occurring within the airways. They also have a dry, hacking, chronic cough and may have nasal discharge.

RAO horses do not have a fever and they are not contagious, although they are at risk of developing other respiratory illnesses such as pneumonia, which will result in fever, lethargy and reduced appetite, and will require antibiotics.

Treatment

Once a horse develops RAO, it can’t be treated, only managed—again, similar to asthma in humans. However, with today’s advances in veterinary medicine, horses with RAO are living better than ever, and many can still continue their athletic careers.

The primary goal of RAO management is to prevent aggravation of the horse’s allergies. This is most effectively done by managing the horse’s immediate environment. Ultimately, fresh air really is the best prescription.

Horses with RAO are best managed when they are kept on pasture full time, even in winter. Being stalled keeps a horse in close contact with dust, mold, and pollen—all of which can trigger a flare of heaves.

Instead, keeping an RAO horse outside helps dilute any contaminants he is inhaling. While some horse owners might be hesitant about keeping an RAO horse outside during the cold winter months, rest assured that the fresh air is more beneficial to the horse’s lungs than a snug stall; however, blanketing and run-in shelter recommendations still apply.

If an RAO horse must be kept in a barn, there are some specific things you can do to help make the immediate environment as low-dust as possible. The first step is to not sweep or distribute hay while the horse is in the barn; these activities merely stir up dust and other particles.

Secondly, do not use straw as bedding. Shavings are preferable, as are other low-dust options including chopped paper or cardboard.

Feeding

Feeding is another aspect to consider for RAO management. Many heaves horses will exhibit clinical signs in winter when it is typical to feed large quantities of dry, dusty hay. Soaking hay in water using a hay net before feeding is helpful in reducing the amount of dust and spores the horse is exposed to, and will help with mild cases of RAO.

However, severe cases may require avoidance of hay altogether. These horses should be slowly transitioned to a pelleted complete feed diet. Avoiding round bales when horses are on pasture also helps, as these types of bales can have high levels of certain types of dust that are particularly irritating to RAO horses.

Medication

Although environmental changes are the best way to manage RAO in the long term, short-term medical solutions are frequently needed when a horse has a flare-up.

If your horse experiences periods of labored breathing due to RAO, your veterinarian will typically prescribe a round of corticosteroids. This medication effectively decreases the amount of inflammation inside your horse’s airways, making it far easier to breathe.

In severe cases of heaves, oral steroids are not strong enough to combat clinical signs. In these cases, the horse requires a more direct method of getting a strong steroid directly into the lungs.

Luckily, there are equine inhalers on the market made specifically for this need. All steroids, whether inhaled or given orally, should be prescribed by your veterinarian.

These medications can have side effects and will have specific dosing instructions that need to be followed exactly. Never give your horse a steroid without your veterinarian’s guidance.

Barn Ventilation

Even if your horse doesn’t have heaves, being mindful of the air quality where he lives is still important, especially in the winter. Barn air can quickly become stuffy when all doors and windows are closed, harming your horse’s respiratory health.

Even if dust doesn’t seem to bother your horse, ammonia from urine is extremely irritating to the sensitive lining of his respiratory tract. Ammonia fumes are mild irritants at best, and at worst can put your horse at risk for respiratory infections.

Even in the coldest of temperatures, air quality will improve if there are some windows open in a barn, even overnight. Air circulation is the key. If air isn’t moving, it’s stagnant and loaded with particles that have the potential to irritate your horse’s airways.

Respiratory wellness is important in all horses, not just those with heaves. Understanding how your horse’s immediate environment interacts with his airways is vital when choosing what’s best for your horse.

ANNA O’BRIEN, DVM, is a large-animal ambulatory veterinarian in central Maryland. Her practice tackles anything equine in nature, from Miniature Horses to zebras at the local zoo, with a few cows, goats, sheep, pigs, llamas, and alpacas thrown in for good measure.

This article originally appeared in the December 2017 issue of Horse Illustrated magazine. Click here to subscribe!

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Q: The vet was just out to look at my 20-year-old horse, who’s become difficult to bridle, picks at his food, and won’t even take carrots from my hand anymore. I kinda figured it was a mouth problem, but my vet said regular floating wouldn’t fix this, that my horse has some kind of new disease (with a bunch of letters) that might mean some teeth have to get pulled. Do you have any idea what she was talking about?

A: I believe you’re talking about EOTRH, which stands for Equine Odontoclastic Tooth Resorption and Hypercementosis. It’s a newly recognized syndrome in older horses resulting in disease and destruction of incisors and canine teeth, and sometimes cheek teeth.

As the disease progresses, the roots of multiple teeth begin to resorb or dissolve, and the body tries to stabilize these teeth by laying down extra cementum (the bone-like substance covering each tooth). This results in hypercementosis or bulbous swellings around the roots of affected teeth. These teeth become infected, abscess, and may loosen or even fracture. In severe cases there may also be significant extension of disease to the bone around the affected teeth.

EORTH is a slowly progressive disease, and it’s unknown at this time what the trigger is that starts the process. It’s believed that the process actually begins well before owners and veterinarians first start to recognize signs.

EOTRH is a very painful condition for affected horses, and chronically affected horses have weight loss, lack of appetite, attitude changes, hypersalivation (drooling), head shaking, discomfort in the bridle, and other signs. It’s known that both periodontal (gum) disease and dental abscesses are painful, and this syndrome causes a significant degree of both, with usually multiple teeth affected. Because horses are quite stoic and adapt to this chronic pain, it’s typically not until the pain is gone (ie the affected teeth are extracted) that you realize how much the disease was affecting them.

A veterinarian may suspect EOTRH during a routine exam or when asked to look at a horse showing signs like yours. However, radiographs (x-rays) are essential to making a diagnosis, because most of this process occurs below the gumline and cannot be seen. Often there are more severe changes present radiographically than what are expected just by looking at the teeth and gums. Radiographs will show whether the horse has more severe resorption or abscessation, or if there is significant hypercementosis present that could make extractions more difficult. Vets use these images to then make a plan for extractions, deciding whether they should be removed in stages (if only a few teeth are affected) or if all the incisors and canines require extraction due to advanced disease.

Regarding extractions, horses tolerate these very well and usually remain standing under heavy sedation with local nerve blocks so they cannot feel anything happening in the mouth. Afterwards, pain medications and antibiotics are usually prescribed. These horses are typically eating a soft, soaked pelleted mash or chopped or pelleted hay before going home the same day and back to normal feed the following day. They generally start feeling better within 24 hours of having chronically infected and painful teeth removed, and owners frequently report a noticeable difference in their behavior and attitude.

If EOTRH turns out to be the diagnosis in your horse after a follow-up exam and radiographs, follow your vet’s advice and in no time your horse should be back to his old self!

The post Ask the Vet: EOTRH appeared first on Horse Illustrated Magazine.

Managing with Medication

Due to its origins in the brain (see “Cushing’s Cause,” below), the bad news is that PPID cannot be cured. However, the good news is that it can easily be managed, especially when caught early. The drug of choice to manage PPID is called pergolide. The first FDA-approved pergolide for use in horses entered the market in 2011 under the trade name Prascend. Prior to this approval, veterinarians had to use other forms of pergolide obtained from compounding pharmacies.

Pergolide is a dopamine agonist, which means it works like dopamine in the brain to regulate and slow production of a hormone called adenocorticotropic hormone (ACTH). A dysfunctional pituitary produces higher than normal amounts of ACTH. This hormone signals to the adrenal glands to produce another hormone called cortisol. Constantly elevated levels of cortisol in a horse’s body produce the clinical signs associated with PPID, such as increased thirst (polydipsia), increased urination (polyuria), long and wavy hair coat (hirsutism), laminitis, muscle wasting, and poor wound healing.

Prascend is available in tablet form and is given orally. An average 1,000-pound horse typically is prescribed one to two tablets once a day, but your veterinarian will calculate the exact dose for your horse based on body weight and the severity of clinical signs.

The most common side effect of pergolide is decreased appetite. If you notice this in your horse, your veterinarian may advise you to reduce the dose for a few days until your horse is eating better, and once he is, increase the dose to the originally prescribed amount.

Food for Thought

One challenge common to horses with PPID is that they are often underweight but sometimes mistaken for being overweight. This is not only because a long, shaggy hair coat can hide a thin body frame, but also because some PPID horses have a potbellied appearance. Horses with PPID are also prone to laminitis. The key for many PPID horses is to provide a diet that is low in starch and sugar, but high in fiber and moderate in fat.

This type of diet rules out alfalfa and grain, for the most part, leaving you instead with grass-based forage and pelleted feeds. Since many PPID horses are geriatric, carefully read the ingredient label on any senior feed your horse may be eating. Some senior feeds are high in starch to pack on the calories. Instead, consider adding a vegetable oil top dressing or rice bran to increase the calorie count for older PPID horses that are hard keepers.

Keeping geriatric needs in mind, some PPID horses may have dental issues and require easy-to-chew food. High-quality grass hay is key for roughage, and pelleted feeds, if given, may need to be soaked to prevent choke.

Some holistic research recommends the addition of antioxidants such as vitamins E and C to a PPID horse’s diet to combat the oxidative damage to neurons that has been linked as part of the cause of PPID. However, studies have not shown that increasing the levels of these vitamins in a PPID horse’s diet actually helps. Before you decide to add any dietary supplement to your PPID horse’s diet, talk with your veterinarian. She can read the ingredient label with you to determine the amount of vitamins actually in the supplement and be on the lookout for additives that may be detrimental, such as sugary binders.

Preventive Care

A PPID horse, even under pergolide management, still has a depressed immune system. This means the horse is more susceptible to infection and the body will take longer to heal wounds. For this reason, it’s imperative to keep your PPID horse up to date on vaccines and have regular physical exams as well as fecal exams for parasites.

Some PPID horses seem prone to hoof abscesses, so make regular hoof trimming and daily hoof cleaning a priority. Routine dental care is also important to your PPID horse’s overall health for two primary reasons. First, many PPID horses are older and often require regular floating to manage sharp points and uneven tooth wear within the mouth. The second reason is many PPID horses, due to their compromised immune system, are susceptible to mouth ulcers. Oral exams with a mouth speculum and light allow your veterinarian a good view of any potential problems between the gums.

Grooming

When started on pergolide, many fuzzy PPID horses will finally shed their excessively long coats. However, not all will shed, or won’t shed completely. If you live in a warm environment, you’ll need to body clip your horse in the summer months. Conversely, don’t assume a PPID horse can grow a coat thick enough to keep himself warm in the winter. Altered metabolism and old age can make it hard for some of these horses to thermoregulate, so a blanket in the winter may still be a good idea. If you notice an exceptionally fuzzy PPID horse getting sweaty in the winter, consider a moderate partial clip.

Regular grooming allows you to keep an eye out for wounds in your PPID horse. With an impaired immune system, wounds are slower to heal and have greater risk of becoming infected, so a small scratch or kick when coming in from the pasture is better to catch and clean early.

Exercise

Should you ride a horse with PPID? The answer comes down to how healthy the animal is overall. If he is thin and has muscle wasting, then no. But a younger animal whose PPID is well controlled via medication and management and that doesn’t struggle with weight or other health issues could still be ridden, although stressful competition should be avoided.

Cushing’s Cause

Back in the old days, a brain tumor was considered the cause of PPID, and an inoperable one at that. After scaring horse owners half to death, the vet who broke the news had to allay fears by explaining there was no need to panic. These tumors were benign, meaning they wouldn’t spread to other parts of the body and they weren’t aggressive. Instead, these tumors—called pituitary adenomas—resulted in the dysfunction of the pituitary gland, a small part of the brain that releases important hormones that communicate with the rest of the body.

Not all cases of PPID are due to a tumor. Recent research has shown that aging can cause a decrease in the production of a neurotransmitter in the brain called dopamine. Dopamine helps keep the pituitary gland in check. When there are lower levels of dopamine in the brain, the pituitary gland produces hormones without restraint. Ongoing research continues to find new levels of complexity to this disease.

After a lengthy discussion, Simon’s owner was feeling much better about the PPID diagnosis. After a few months on daily mediation, some diet changes and some management checks, Simon shed his shaggy coat and wasn’t drinking as much water. Simon was clearly feeling better, and so was his owner.

A Brief History

Humans can also suffer from Cushing’s disease, although a different part of the pituitary gland is affected. The American neurosurgeon Harvey Cushing was the first to describe the condition (in humans) in the early 1900s. The equine version wasn’t documented until the 1960’s. Once called “equine Cushing’s syndrome” then “equine pituitary pars intermedia adenoma”, experts currently favor PPID (pituitary pars intermedia dysfunction) or simply equine Cushing’s disease.

This article originally appeared in the August 2015 issue of Horse Illustrated magazine. Click here to subscribe!

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Signs of a Problem

Any irregular limb movement or foot placement should be cause for concern, particularly erratic voluntary movement. Your horse might demonstrate some mild but unusual gait changes, such as dragging a toe, or inconsistent lameness with or without a head bob. Or, he might display something more obvious such as staggering and incoordination (ataxia) and/or muscular weakness (paresis).

Ataxia is quite worrisome as the horse may stumble or lose his balance, and he might actually fall down.

Abnormal posture—the way the horse stands or leans and the way he holds his tail and/or neck—is another sign of a neurologic issue. Cranial nerves may be affected so that there is difficulty chewing, swallowing and seeing, or you may notice a droop in his lip or eyelid.

Neurologic cases can also show a changed disposition or altered reaction to stimuli; a horse may be mentally sluggish, or some individuals may be hyper-reactive to sound.

Neurologic Exam

A thorough physical examination by your veterinarian is key to determining the horse’s problem. Limb placement tests a horse’s understanding of where his legs are in space. This is done by placing one leg in front of the opposite leg and watching if and how long it takes for the horse to replace it to a normal position. (However, some normal horses will stand for a long time with their legs crossed because they are cooperative, not due to a neurological problem.)

Pulling on a horse’s tail or pulling on his halter is a method to assess a horse’s muscular strength. You should not be able to pull a horse off his feet with either of these tests. Pushing hard against the horse’s torso also should not cause him to move or lose balance.

Another test your vet may perform involves holding up a front leg and asking the horse to move forward as he hops on the opposite leg; this also tests strength (or weakness) in the legs as well as coordination.

Walking a horse up and down an incline is another checkpoint for both stability and awareness of leg placement.

The cranial nerves can also be affected by neurologic conditions. These control the ability to take hold of food, swallow, hear, see, smell, taste, salivate and touch, as well as control specific muscles of the eyes, tongue and facial region. Your veterinarian will assess these during the exam.

Other Diagnostics

Other tests help confirm your vet’s diagnosis. Radiographs, MRI and/or CAT scan evaluations examine bone structures for trauma, locate masses or tumors, and check the neck for compression on the spinal cord. Analysis of cerebral spinal fluid is useful for identifying parasitic invasion, viral or bacterial infection. Blood can be tested for antibodies related to specific infections.
There are many possible neurologic conditions; here are some of the more common ones.

Wobbler Syndrome

Cervical vertebral malformation or instability, more commonly known as wobbler syndrome, describes incoordination caused by the narrowing of the spinal canal that impinges on and compresses the spinal cord in the neck region.

It is thought that a combination of factors leads to wobbler syndrome: rapid growth rates in young horses, dietary imbalances of minerals, high energy levels, excess activity, and genetic predisposition. A younger horse identified with narrowing of the spinal canal may be a candidate for surgical correction.

An older horse may also develop wobbler syndrome due to osteoarthritis and/or age-related degenerative changes, particularly if he is predisposed due to a relatively narrow spinal canal.

Mosquito-Borne Viruses

The main viral offenders to the neurologic system in the U.S. are western encephalomyelitis (WEE), eastern encephalomyelitis (EEE) and West Nile virus.

The good news is that all three of these mosquito-borne viruses are preventable through safe and effective annual vaccination prior to insect season. In more southern climates, it may be necessary to immunize twice a year. Mosquito-control strategies are also important. However, a horse infected with any of these viruses is not contagious to other horses or humans.

Rabies

Rabies is particularly scary because it is fatal to the animal and is highly infectious to other horses and humans.

A rabies-infected bat, skunk, fox, or raccoon may bite a horse without an owner being aware that this has occurred. A rabid horse typically doesn’t foam at the mouth or become aggressive. Instead, the horse may appear as if he is slightly off or just doesn’t feel well. People caring for the horse may not recognize a possible rabies case until obvious behavioral changes and neurologic signs become evident. By then, many people may have been exposed.

The best cure in this case is prevention. Every horse should be immunized annually against rabies. There is no excuse not to; the vaccine is safe, effective and inexpensive.

Equine Herpesvirus (EHV-1)

Also called rhinopneumonitis, one strain of equine herpes virus (EHV-1) that more typically causes respiratory infections is also known for its dangerous attack on the blood vessels within the nervous system. Incoordination, poor bladder control, weakness, and recumbency are associated with this disease.

To date, there is no available vaccine against the neurologic form, and it is highly contagious between horses. The best prevention is to implement good biosecurity procedures on your farm; isolate newcomers for several weeks, for example. Also, when participating in events off the farm, don’t permit your horses to comingle with others or to eat or drink from communal sources of food or water.

Equine Protozoal Myeloencephalitis (EPM)

EPM is caused by a protozoan parasite, Sarcocystis neurona, that invades the central nervous system. Clinical signs vary, but usually symptoms are associated with the spinal cord: incoordination, stumbling, weakness. Muscle wasting along the topline and haunches is also common.

Opossums are the most common means of transmission when they contaminate horse feed and/or water with their feces. Blood samples may yield a positive result, but all that tells you is that the horse has been exposed, not that he is necessarily infected. Diagnosis is based on clinical signs and testing of a cerebral spinal fluid tap.

Treatment relies on a course of drugs for three to four months. Sixty to 70 percent of treated horses are able to return to athletic function.

Lyme Disease

A tick-borne disease, Lyme disease (caused by Borrelia burdorferi bacteria) typically causes orthopedic issues related to joint pain and lameness, as well as fever and weight loss, but is also known for various neurologic symptoms: depression, incoordination, head tilt, encephalitis (inflammation of the brain), and skin hypersensitivity. If not diagnosed quickly, this can turn into a chronic condition that is more difficult to treat. Blood testing can identify antibodies that have developed from exposure to B. burdorferi.

A new form of testing was developed at Cornell University several years ago that differentiates between early and late stages of infection.

Equine Motor Neuron Disease (EMND)

EMND is a progressive disease that affects the nerves supplying all muscles. This syndrome is thought to be associated with high copper levels and vitamin E deficiency. There is no treatment for EMND, and the horse will eventually die.

Other Neurologic Syndromes

Other neurologic syndromes exist, including tetanus, botulism, moldy corn poisoning, toxic plant poisoning, middle or inner ear infection, cerebellar abiotrophy in Arabian foals, and various trauma-related problems to spine or brain.

A thorough veterinary exam taking into account the breed and history of the affected horse will help to identify the cause.

NANCY S. LOVING, DVM, is a performance horse veterinarian based in Boulder, Colo., and is the author of All Horse Systems Go.

This article originally appeared in the October 2015 issue of Horse Illustrated magazine. Click here to subscribe!

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