A foal born to a neurologically impaired dam is unlikely to mimic his mother's unusual behavior. Photo © EQUUS

Q: If a mare with neurological problems gives birth, will the foal mimic her odd behavior? This is an ongoing debate at our barn. Some people are theorizing that as mom walks, baby walks, and as mom eats, baby eats. I understand that some foals, however, can be born with neurological diseases. Can you help us settle this?

A: Although it is true that foals sometimes mimic the behavioral patterns of their mothers, those born to mares with neurological issues generally do not imitate those deficits. At our neonatal intensive care unit, we have delivered many foals from mares who were afflicted with equine0 protozoal myeloencephalitis (EPM), one of the more common infectious neurological diseases seen in horses. These foals do not display any of the neurological signs their mothers do.

However, foals can be born infected with organisms that cause neurological disease that are passed down from the mother. For example, studies show that one of the organisms that can cause EPM, Neospora hughesi, can be transmitted via the placenta to the fetus carried by some naturally infected mares; however, the foals who were found to be infected with the protozoa did not necessarily demonstrate neurological signs for up to three months after birth. Likewise, transmission of the highly contagious equine herpesvirus type-1 (EHV-1) can also occur from the dam to the fetus via the placenta, but while these foals are born with EHV-1 in their bloodstream and various organs (lungs, liver, thymus), the majority of them do not show any neurological signs.

The most common cause of neurological disease seen in the newborn foal is neonatal encephalopathy. This can occur when the fetus is deprived of oxygen in the womb because the placenta is not functioning properly, usually because of a bacterial infection (placentitis). In cases like these, the foals are born with neurological abnormalities, such as incoordination and lack of the suckle reflex. Neonatal encephalopathy may also develop in foals who are deprived of oxygen for too long during the birthing process, as we often see with difficult deliveries (dystocias); these foals generally do not develop neurological signs for up to 18 to 24 hours. In both scenarios, the lack of oxygen leads to fluid accumulation in the brain tissue (cerebral edema), and damage may also occur to other organ systems, such as the kidneys and gastrointestinal tract. The prognosis for these foals is generally very good if they are treated early and appropriately.

Rodney L. Belgrave, DVM, DACVIM
Director of Internal Medicine
Mid-Atlantic Equine Medical Center
Ringoes, New Jersey

An additional horse (Wellington area and no identified direct or indirect connection to the Ocala show grounds) has been tested and found to be EHV-1 (wild strain) positive. There

have been no neurologic symptoms associated with this animal.

All horses on the HITS Showgrounds, Ocala are under quarantine. Additionally, horses believed to have

had increased opportunity of exposure or other risk have been traced to 11 different farms/training facilities. Quarantines have been put in place and the animals are being monitored for evidence of illness.

The Florida Department of Agriculture has posted a detailed report regarding this situation and is updating the report regularly. These updates include links to additional resources and are available at: www.freshfromflorida.com/ai/pdf/EHVWebsiteUpdate.pdf

Please check this source regularly for the most current and reliable information regarding the status of the disease.

The equestrian community is being advised of the importance of horsemen implementing good biosecurity protocols that should be routine when attending competitions or visiting other venues where horses of different origin and disease status are congregating. If planning to travel to such venues, make certain you contact the venue prior to travel to understand what biosecurity measures have been imposed. Additionally, it is advised that you consult with your veterinarian in evaluating your horse's current vaccination and immunity status and to review or develop an individual biosecurity plan. The California Department of Food & Agriculture has published a bio-security tool kit at this link: http://www.cdfa.ca.gov/ahfss/animal_health/equine_biosecurity.html. Dr. Stephen Schumacher, Chief Administrator for the USEF Drugs & Medication Program describes this as a "good comprehensive resource compiled from a number of sources."

Confining sick horses in a quarantine stall protects the health of his barnmates.

EHV Outbreak.
Horses Euthanatized.
Farms Quarantined.
Travel Restricted.
Shows Cancelled.

Headlines like these will catch any horse owner’s attention---usually, we all hope, with a sigh of relief that the outbreak is somewhere far away.

But that’s not always the case. Outbreaks of EHV-1, which may involve a potentially fatal strain of the equine herpesvirus that can produce neurological impairment, are not uncommon. The virus might crop up on one farm or a small cluster of farms somewhere in the country every year. Under the right circumstances, however, the outbreak can become widespread. When the disease appeared at the National Cutting Horse Association’s Western National Championships in Ogden, Utah, in the spring of 2011, each one of the 400 horses in attendance had some risk of exposure---and the threat wasn’t identified until all had returned to farms and ranches across 19 Western states.

For weeks that May, a number of shows and events were cancelled, and several barns and state veterinary hospitals were put under quarantine as new outbreaks cropped up in state after state from Washington to New Mexico. By the time the USDA-APHIS (United States Department of Agriculture’s Animal and Plant Health Inspection Service) declared the virus “contained” in late June, 33 cases of myeloencephalopathy caused by EHV infection had been confirmed in 10 states; 26 of those horses had attended the event in Ogden, Utah, and 13 died or were put down.

Yet officials say the 2011 EHV outbreak could have been far worse. Prompt action on the part of state and local animal health officials, veterinarians, event organizers and---most important---horse owners helped halt the spread of the virus.

If EHV or another contagious equine disease broke out near your property, would you know what to do? By establishing a plan now, and having a few basic materials and supplies on hand, you could not only protect the lives of your own horses, you could help prevent the next outbreak from growing into an epidemic.  A good biosecurity program need not be difficult or complex. In fact, your normal management practices are probably already covering most of the bases. Still, it’s a good idea to review your routines periodically just to make sure you’re not leaving any gaps, and to make plans for what you’d do in the event of a real emergency. Your veterinarian will help you tailor a program to your individual needs. Here’s where you can start.

Keep vaccinations up to date
Vaccination is an inexpensive but effective way to prevent your horse from contracting several serious diseases. The American Association of Equine Practitioners (AAEP) recommends that all horses receive vaccines against a “core” group of diseases: tetanus, eastern/western equine encephalomyelitis, West Nile virus and rabies. An additional eight vaccines are available for horses at risk of encountering diseases such as Potomac horse fever, strangles or EHV.

Which of these risk-based vaccinations a horse needs depends on several factors, including his geographic location, age and activities. Those who are frequently transported to horse shows, for example, require more protection than most “homebodies,” and the needs of a pregnant mare are different from those of a retired gelding.

Your veterinarian is your best resource for creating a vaccination protocol tailored to your horse. Especially if you’ve made any significant management or lifestyle changes in recent years, ask her to review your routine to make sure you’re still providing the appropriate protection for your horse.

Practice good daily hygiene
A number of diseases---including rhinopneumonitis, strangles and equine influenza---can be passed from horse to horse on human hands and with shared tack and equipment. Here are several tips for reducing the chances that you’ll inadvertently spread an illness around your barn:

• Wash your hands after handling each horse. Cleansing your hands is one of the simplest yet most effective ways to avoid spreading infections. Develop the habit of washing with soap regularly, and consider installing wall-mounted dispensers of hand sanitizer between stalls or in other strategic locations. If your barn receives visitors, post signs to discourage the practice of going from stall to stall to pet each horse in turn.

• Scrub water buckets and automatic waterers regularly. Keep one dedicated brush for each bucket. Also, never let the end of the hose touch the surface of the water as you fill the bucket.

• Keep equipment separate. Ideally, each horse will have his own dedicated grooming brushes, blankets and sheets, bits and other items. Colored duct tape is a good way to mark each item to help avoid mix-ups---assign each horse his own color and use it to “tag” all of his equipment. Also, avoid sharing items with strange horses at shows or other events.

• Disinfect equipment periodically. Practically everything that touches your horse picks up bacteria and other pathogens as well as dirt and grime. Machine washables, such as towels, blankets and saddle pads, can be disinfected in regular laundry cycles, but some higher end washers now feature sanitization cycles, which use steam or extra high heat to kill even more bacteria. Buckets, hoof picks and other impermeable objects can be disinfected with soapy water, bleach or other commercial cleaners (see “How To: Disinfect Buckets, Brushes and Other Tools,” opposite). Sponges are difficult to disinfect. Discard and replace them whenever they get dirty.

• Control rodents. Rats can carry several diseases that affect both horses and people. Keep grain bins sealed, and promptly clean up any feed spills to deter vermin. Barn owls, cats and other predators will help keep populations down.

• Manage manure responsibly. Some pathogens may be passed via contact with manure. Pick up wastes daily, and avoid tracking it around with your boots or wheelbarrow wheels. If you are caring for a sick horse, place a disinfectant footbath at your barn entrance. To make one, place AstroTurf or a textured welcome mat in a shallow basin and cover it with a 10 percent chlorine bleach solution. Then, step into it to scrub the organic material off the bottom of your boots as you enter and exit the barn, changing the footbath water as it becomes dirty.

Quarantine new or sick horses
A number of contagious diseases can be spread directly from horse to horse. “Modes of transmission include direct contact, inhalation, oral [ingestion], via open wounds or bites and venereal contact,” says Roberta M. Dwyer, DVM, professor at Maxwell H. Gluck Equine Research Center.

If you have a stable herd---a group of horses who live together and travel infrequently---chances are you’ll need to implement quarantine measures under only two circumstances: when you actually have a sick horse, and when you introduce a new horse.

Horses exposed to a number of common equine diseases may show no signs for a week or more, yet they are capable of passing the pathogens on to others. For example, a horse can easily be exposed to strangles or rhinopneumonitis at an auction, then carry the disease to the herd at his new home.

“New horses should be quarantined for at least two weeks prior to joining the herd,” says Dwyer. “Two weeks covers the incubation period for many equine infectious diseases, like influenza.” If the horse has a vague history or you’re unsure about his vaccination status, it’s wise to extend the isolation period to at least 21 days.

“New horses should have their temperatures taken twice daily for early detection of disease,” says Dwyer. Call your veterinarian at the first sign of fever. It’s also a good idea to monitor the temperatures of your resident horses during this time.

Another risk occurs when you have some horses who always stay at home but share space with others who do go to shows. The traveler could easily pick up an illness and spread it to the rest of the herd before you know he’s sick.

Have an action plan ready
To avoid wasting time in the event of a disease outbreak, establish an action plan. Keep on hand equipment and products that are necessary to clean and disinfect stalls, including plastic booties, gloves and protective coveralls. Consider how you would manage the practical aspects of isolating one or more members of your herd, and make sure you have ready access to your horse’s veterinary records, particularly his vaccination history.

Once you’ve developed a plan for dealing with sick horses, make sure everyone else who has access to your farm or works in your barn knows the procedures, too. Either meet with individuals informally or schedule a training session so that everyone knows how to recognize the first signs of illness and what to do if they spot something.

If an outbreak occurs in your area, get your information from reliable sources. Be wary of social media: When people panic, rumors run rife. Instead, rely on your veterinarian, your state veterinarian’s office or your state’s department of agriculture for updates. Sources like these will have websites with pages dedicated to news releases and alerts. Find the sites likely to cover your area, and bookmark them in a dedicated folder so you’ll be able to find them quickly in an emergency. Don’t forget to include the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) at www.aphis.usda.gov.

Keep in mind that, even if a disease outbreak in your region does not affect your farm directly, equine transport may be restricted. You’ll find updates and bulletins on the state or federal websites.

Last year’s EHV-1 outbreak is behind us. It was contained in part due to the efforts of the National Cutting Horse Association’s quick response in spreading the word and voluntarily canceling events. But the countless individual owners, who heeded the warnings and kept their horses home, helped prevent a handful of cases from growing into a widespread epidemic.

Given the nature of this virus as well as other contagious diseases, similar outbreaks are certain to happen again. While you can’t guarantee your horse will never get sick, you can take steps to minimize his risks and the threat of the illness spreading. And that will benefit not just the residents of your own barn, but also the welfare of horses all around your state.

At Rancho Sierra Vista Equestrian Center in San Juan Capistrano, California, bad news came on the heels of the new year. “A little cough had been making the rounds of the barn, and we were on alert for that,” recalls trainer Cathy Hanson, who stables 30 horses at the 350-horse multidiscipline facility. “But in early January one horse developed neurological signs, and that prompted testing.”

The blood test came back positive for a form of equine herpesvirus-1 that can cause potentially fatal neurological disease in horses. “EHV is everywhere, and it’s super-contagious,” Cathy says. State animal health officials were called in, and on January 10 the facility was quarantined.

An outbreak of contagious disease is a nightmare at any barn, let alone a facility home to so many horses. This was the first such incident for Rancho Sierra Vista, but it was just one of several outbreaks that have put riders on edge around the United States in recent months. The list of disease-causing organisms that spread horse to horse includes viruses like EHV and equine influenza as well as bacteria like Streptococcus equi, which causes strangles. How can you protect your horse?

“We won’t be able to prevent all cases of these diseases,” says Josie Traub-Dargatz, DVM, MS, DACVIM, an equine disease expert at Colorado State University. But that doesn’t mean you’re helpless. In this article, Dr. Traub-Dargatz explains how you can ­assess—and reduce—the risks your horse faces. Those risks are greater if he lives at a big commercial boarding stable or is a regular on the show circuit than if he lives in your backyard and just makes a circuit of the pasture. But he faces some danger of infectious disease anytime he comes in contact with other horses.

Get the Facts First
Word of disease outbreak travels fast these days, via Facebook, Twitter, online forums, text messages, and email. “Social media can get information out extremely quickly,” Dr. Traub-Dargatz says, “but the accuracy of the information may be open to question.” To assess risk, you need to separate facts from rumors and exaggerations.

Some contagious equine diseases are reported to state animal health officials, and that makes it fairly easy to get reliable information about an outbreak. For example, in California, neurological cases caused by EHV-1 must be reported to the state Department of Food and Agriculture. During the San Juan Capistrano outbreak this allowed everyone to get frequent and accurate updates on the CDFA website, where outbreaks are categorized by county instead of by naming specific facilities. Reporting requirements for equine diseases vary state to state, so check with your state’s animal health officials to find out which diseases are reportable where you live.

Reporting requirements helped check a multistate outbreak in 2011, when more than 400 horses were exposed at a cutting-horse event in Utah and went home to barns in 19 states and Canada before the first case was recognized. State and federal officials worked closely to track the horses and get accurate, timely information to the public.

When the disease isn’t reportable to state animal health officials, getting information is much more complicated. For instance, California doesn’t require reporting for equine flu or common forms of EHV that cause respiratory disease in horses and abortion in pregnant mares. Where should you turn? Your veterinarian is the most likely source of reliable advice, but with no central clearinghouse for information it can be a challenge to get the facts.

The American Association of Equine Practitioners has formed a task force to develop a communications plan for disease outbreaks. (This is part of an effort by the American Horse Council to create a national equine health plan.) “The goal is to make sure owners and managers of events and horse facilities, industry associations, extension agents, horse councils and veterinary practitioners all have accurate information quickly, acknowledging that the source of that information may vary,” Dr. Traub-Dargatz says.

The task force will develop a draft plan and send it to the American Horse Council for industry input, so there’s an opportunity for horse owners and event organizers to get involved, she adds. “Think about what diseases you need to know about and what your concerns are. You can voice those concerns to breed or discipline associations or to your state horse council, which all communicate with the AHC.”

In January, California authorities reported new cases of equine herpes virus myeloencephalopathy (EHM), the neuropathic for of equine herpes virus (EHV-1, commonly known as "rhino"). After the outbreak in mid-May 2011, H&R reported on biosecurity measures in the Emergency! section. Review those tips from contributing veterinarian Dr. Barb Crabbehere.

If there were an outbreak of an infectious equine disease in your locality, would you know how to keep your horses safe? Or what to do if they were exposed—or became ill?

We asked H&R’s contributing veterinarian, Dr. Barb Crabbe, for a step-by-step checklist to cover the various scenarios. Here’s what she told us.

Get Informed
First, don’t panic. Turn to a reliable source, such as your veterinarian, your local veterinary teaching hospital, or appropriate state/federal officials for accurate information that applies to your area.

Avoid Exposure
You needn’t automatically enact a stay-at-home policy unless your vet recommends it. But don’t take your horse anywhere there’s a known risk for the outbreak—such as a facility where horses are known to be sick.

Consult your vet about potential vaccination protocols (though there won’t always be one, depending on the disease).

Monitor/Isolate Exposed Horses
If your horse does inadvertently become exposed to a contagious disease, isolate him for at least two weeks (30 days is the ideal) in a stall or pen at least 30 to 40 feet away from other horses. Monitor his temperature every day, notifying your vet if it rises.

Contain Contagion
If your horse becomes ill, work with your vet to provide appropriate care while keeping the sick animal isolated from other horses. A separate barn is ideal, or else designate a quarantine area at the far end of your barn, away from other horses and the main traffic area.

Use duct tape on the barn floor so everyone knows where the quarantine area is. Wash your hands thoroughly before and after tending the sick horse, and keep hand sanitizer available for additional cleanings and for visitors to use. Follow disinfection techniques with all equipment that comes into contact with the sick animal (see “Disinfection” below). Always tend to sick or exposed horses last in your daily routine.

Establish a dedicated wheelbarrow and fork for cleaning the quarantined stalls; burn or otherwise safely dispose of the bedding. Designate one pair of rubber boots and rubber gloves, plus perhaps coveralls to use whenever you’re in the quarantine area; then remove them and leave them for use there only.

If need be, set up a shallow basin full of properly mixed disinfectant so other individuals can wash off their footwear before leaving the quarantine area.

Routine Biosecurity
As May’s equine herpes virus outbreak reminded us, a program of good, ongoing protective measures (popularly known as “biosecurity”) is your first, best line of defense against infectious diseases. Follow these recommendations:

At Home

• Work with your vet to set up a vaccination plan for all horses in your care.
• Be sure all horses entering your facility (or the one where your horse is boarded) are appropriately vaccinated and free of all communicable diseases; ideally, isolate all incoming horses for up to 30 days.
• Don’t share water or feed buckets, grooming equipment, or any piece of gear that may come into contact with a horse’s eyes, nose, or mouth.
• When cleaning or filling water containers, don’t allow the hose nozzle to touch the container.
• Remove all manure/waste products to a location away from the barn.
• Limit horses’ exposure to disease-spreading pests such as flies and mosquitoes.

When Traveling

• Monitor temperatures prior to traveling, and don’t ship a horse that’s had a fever within five days of a haul.
• Keep a disinfectant-filled spray bottle handy to disinfect stalls and stable areas before moving your horse into a show grounds or other new facility. (Spray liberally.)
• Don’t use common water buckets or feed areas at shows or event grounds.
• Don’t borrow/share halters, twitches, lip chains, or other items that may touch a horse’s eyes, nose, or mouth.

Disinfection
Items that can be disinfected when necessary include nylon halters, bits, lip chains, grooming equipment, stalls, buckets, shovels, pitchforks, and even shoes and car/truck tires.

Remove all excess dirt/debris from items to be disinfected, including stall floors and walls.

Wash the item or area first with laundry detergent or dish soap.

Immerse or thoroughly wet the item/area with an appropriate disinfectant. Products that are phenolic-based (Lysol) or quaternary ammonium-based (Roccal D) are most effective. (Although bleach is effective against most viruses and bacteria, it’s inactivated by organic material, making it less-than-ideal in a barn situation.)

Rinse the disinfectant off thoroughly with plain water.

Your horse hesitates and steps awkwardly when he walks downhill. He’s dragging his toes, too, and a few times he has even stumbled while trotting in the ring. He doesn’t seem sore, and your trainer and farrier don’t see anything wrong with his feet—but you know he’s not right. Could he have one of several equine neurological disorders, like equine herpesvirus type 1 (EHV-1) equine protozoal myeloencephalitis (EPM) or West Nile virus?

Owners dread equine neurological disorders, such as equine herpesvirus type 1, equine protozoal myeloencephalitis or West Nile virus, and no wonder. Many of these problems are hard to diagnose and hard to treat, and they can damage a horse’s nervous system in ways that leave him unsafe to ride. But every neurologic case doesn’t end badly, and quick action—recognizing signs, getting a diagnosis and starting appropriate treatment—can give your horse the best chance.

If you think your horse might have a neurologic problem, it’s time to call your veterinarian. What exactly will your vet do, and what disorders might she find? In this article, we’ll walk you through a standard neurologic exam, tell you what else may be needed to make a definitive diagnosis and give you an overview of the most common problems.

Sorting Out the Signs
Signs of neurologic problems in horses run the gamut—seizures, abnormal behavior, abnormal gait, facial paralysis and more, says Debra Sellon, DVM, professor of equine medicine at the Washington State University College of Veterinary Medicine. “The most common neurologic problem equine veterinarians see in the United States is an abnormal gait,” Dr. Sellon says. “Affected horses are usually ataxic and weak, meaning that they walk with a staggering or drunken type of gait. They may drag their toes, stumble frequently or sway back and forth when they walk.”

Disruptions in a horse’s command and control system create these problems. For normal movement, nerve signals must flow from his brain along his spinal cord to the nerves that govern his muscles—and nerves must signal back to his brain, reporting where his limbs are. If the signals don’t get through, your horse may become uncoordinated or develop abnormal gaits.

Many neurologic disorders can disrupt the signals. In most parts of North America, Dr. Sellon says, the most common are equine protozoal myeloencephalitis and cervical vertebral malformation (“wobbler syndrome”). But there are plenty of others, including injuries, several viral diseases and degenerative conditions, such as equine degenerative myeloencephalopathy, which has been linked to vitamin E deficiencies in young horses.

“Veterinarians use a fairly standard ­approach to determine a diagnosis for horses with neurologic disease,” Dr. Sellon says. The process begins with gathering information on your horse’s history. When did he begin to stumble or show other signs? Has he fallen? Information on your horse’s age, breed and use is important ­because some neurologic problems are more common in certain groups of horses.

Step two is a thorough physical ­examination. This exam may reveal soreness or other non-neurologic causes for your horse’s signs, or it may turn up signs of an injury or a disease that produces neurologic problems. As she examines your horse, your vet compares the right and left sides of your horse’s body, looking for asymmetry and loss of muscle mass (atrophy) that may develop when muscles go unused, as happens in some neurologic conditions. She may check the range of motion in his neck by encouraging him to bend to each side, using a carrot or another treat as a lure. Limited range of motion may mean an injury or even fractured vertebrae in his neck (the cervical spine).

Neurologic Exam
The third step is a detailed neurologic examination. “The goal is to determine, to the best extent possible, the site in the nervous system that is affected,” says Dr. Sellon. By finding out which functions are impaired, your veterinarian can figure out which nerves are involved. The process, called lesion localization, typically ­includes these steps:

General assessment: Your veterinarian observes your horse’s mental status and behavior. Is he alert or ­lethargic? Standing or down? Wandering aimlessly, circling or showing other odd behaviors or postures?

Basic reflexes: This part of the exam starts at the head with tests of the cranial nerves, which are involved in functions like hearing, vision, swallowing and facial sensation and muscle control. To test ­vision, for example, the vet quickly moves a hand toward your horse’s eye to trigger the menace reflex; your horse should blink and perhaps jerk away.

Along your horse’s neck and back on each side of his spine, your vet uses a ballpoint pen or similar object to touch your horse’s skin. A light but firm touch should trigger the panniculus reflex, the skin twitch you see when your horse is pestered by a fly. Lack of a reaction in any area suggests a problem with the nerves that supply that region. At the hind end, the vet checks muscle tone by lifting the tail; a limp tail may be a sign of a spinal cord problem. When his anus is gently stimulated, it should pucker and your horse should clamp his tail.

Maneuvers in hand: These tests show if your horse has control of his limbs and knows where his feet are. The vet watches as your horse is backed and turned in very tight circles in both directions to see how he places his feet. A normal horse keeps his rhythm and steps under his body, while a horse with a neurologic problem may interfere, take confused steps, swing a hind leg wide or pivot on one leg.

On a slope: Your vet may ask to see your horse led up and down a slope, to see if he stumbles, drags his toes or shows other gait abnormalities. Repeating this test with your horse’s head raised sometimes makes the signs more obvious.

Tail pull: This helps your vet assess your horse’s balance, strength and reaction time. As a handler leads your horse forward, your vet grasps his tail and pulls it firmly to the side. A normal horse will resist the pull; a horse with a neurologic problem may be tipped off balance. The test is repeated on the other side.

Foot placement: These tests help determine your horse’s awareness of his limb position. Your vet takes each foot in turn and places it over its opposite number—left front over right front, right front over left front, and the same behind. A normal horse will immediately put each foot back where it belongs; a horse with a neurologic problem may leave one or more feet out of place for a time.

By the end of the exam your veterinarian should know whether your horse’s problem is neurologic and, if so, what areas of his nervous system are ­involved. She may not have enough information for a clear diagnosis yet because many neurologic disorders have variable signs. “Horses with EPM can show a wide variety of signs, ranging from ataxia and weakness, to individual nerve paralysis, to seizures, to problems with urination or defecation,” Dr. Sellon says. “The vast majority of wobblers present for examination with ataxia and weakness of all four limbs. That means a horse with EPM often looks different from a wobbler but sometimes looks just the same.”

Still, your veterinarian will have enough information to make a list of the diseases or disorders that are most likely the cause and then choose the most appropriate diagnostic tests to confirm or rule out the items on that list. Here’s what you can expect for three common conditions.

Your horse was a star at last week’s show, but now his nose is dripping, he’s coughing persistently and he’s moping in his stall. What’s his problem? When those signs appear suddenly, suspect an upper-respiratory infection—especially if your horse has been to a show or other event where he might have been exposed to infectious viruses or bacteria. Fall and winter are prime times for these ­infections (in horses as well as in people), and a recent nationwide surveillance study shed light on some common causes.

Dr. Nicola Pusterla, ­associate professor in the Department of Medicine and Epidemiology at the University of California, Davis, led the study, which was published earlier this year in the Veterinary Record. He and fellow UC Davis researchers focused on four pathogens (disease-causing agents) that cause upper-respiratory infections in horses—Streptococcus equi subspecies equi, the bacteria that cause strangles; equine influenza virus (EIV); and equine herpesvirus types 1 and 4 (EHV-1 and EHV-4).

From March 2008 to February 2010, they analyzed blood and nasal-swab samples from 761 horses, mules and donkeys with acute clinical signs, such as fever, nasal discharge and coughing. They used real-time polymerase chain reaction analysis, a sensitive testing method that looks for the nucleic acid of infectious agents and can provide answers in as little as 24 hours. The samples were sent in by veterinarians in 23 states, along with information about each case.

Besides helping practicing veterinarians get a quick and accurate diagnosis during outbreaks of these diseases, the researchers hoped the study would provide a picture of the prevalence of major respiratory pathogens in the United States, help match the pathogens with specific clinical signs and evaluate the effectiveness of vaccination programs. Here are some of the findings:

• Samples tested positive for one or more of the four pathogens in 201 cases, about 26 percent of the total. Fifteen of these horses were positive for two pathogens, and one had a triple infection.
• The highest detection rate was for EHV-4, which turned up in 82 cases. Infections with this virus (which can also cause pregnant mares to abort) were most common in fall and winter.
• Next most common was EIV, with 60 cases. It occurred mainly in winter and spring.
• S. equi, also most frequent in winter and spring, showed up in 49 cases. It was common in horses ages 6 to 10, while EHV-4 and EIV infections were more common in 1- to 5-year-olds.
• EHV-1, which can cause neurological disease as well as upper-respiratory infection and abortion, ranked last, with 23 cases. It was generally seen in older horses and, like the other infections, was less common in summer.
• Many affected horses had been vaccinated against these pathogens at some point. For example, half the horses known to have been vaccinated against S. equi tested positive for that pathogen. Ten of 12 horses known to have been vaccinated against EHV-1 were positive for the virus. “Horses were not adequately vaccinated in general, although the vaccine history was sketchy for most,” Dr. Pusterla says. “Vaccine protocols should be tailored to the needs and risk of exposure of each horse.”
• Detection rates for some infections varied among breeds. “I believe this can be explained by differences in management practices,” says Dr. Pusterla. For example, the EIV and strangles groups included high numbers of Quarter Horses. “These horses often enter the show arena at a young age when they are more susceptible to infection,” Dr. Pusterla notes. Moreover, he adds, the study sample may have been skewed because almost half the submissions came from states geared toward the Quarter Horse industry.
• What about the 560 samples that tested negative for all four pathogens? Maybe better tests are needed, or maybe those samples weren’t properly collected. Or maybe ­unknown pathogens were at work—the researchers don’t know.

The research highlights the need to vaccinate and be alert for respiratory infections and to take steps to limit their spread. Call your veterinarian if your horse shows signs—snotty nose, persistent cough, fever, labored breathing, a depressed attitude or loss of appetite. Once diagnostic work pins down the type of infection you’re dealing with, your veterinarian can outline treatment for your horse and measures to keep the infection from jumping to other horses in your barn. Until then, don’t let him mix with others—and if he has already, monitor them for signs of illness and keep them separate. Because handlers and equipment can carry some pathogens from horse to horse, infected horses should also have separate equipment for grooming and stall cleaning and should be dealt with last, after other horses. Wash up thoroughly afterward, and disinfect equipment.

This article originally appeared in the October 2011 issue of Practical Horseman magazine.

EQUUS magazine’s medical editor, Joe Bertone, DVM, MS, DACVIM, fielded questions from participants regarding the latest outbreak of EHV-1 as well as providing expert perspective on the virus. Bertone, a professor of equine medicine at Western University of Health Sciences in Pomona, California and long time contributor to EQUUS, recently became the magazine’s medical editor. He specializes in pharmacology and is currently researching the effect of medications on equine physiology. He received his master of veterinary clinical sciences from Colorado State University and his veterinary degree from Cornell University.

“This was a terrific opportunity not only to provide the facts and a bigger picture view of the EHV-1 outbreak, but also for our new medical editor to connect directly with readers,” said EQUUS Associate Publisher Bob Kliner. “Dr. Bertone’s involvement in the webinar reflects his contributions to our publication. He presents the latest medical research, the practical aspects critical to horse owners and a perspective gleaned from decades in the industry.

For the latest on EHV-1, go to EquiSearch.com, the online home of EQUUS.

What can we learn from this most recent EHV-1 outbreak?
How do we know when it’s safe to travel with our horses?
What can we do to protect our horses from this and similar viruses in the future?

EQUUS Medical Editor Joe Bertone, DVM, MS, DACVIM, is a professor of equine medicine at Western University of Health Sciences in Pomona, California. Bertone specializes in pharmacology and is currently researching the effect of medications on equine physiology. He received his master of veterinary clinical sciences from Colorado State University and his veterinary degree from Cornell University.

While there have only been a few isolated cases of equine herpesvirus-1 (EHV-1) our area (Boulder), it is possible the virus is still in incubatory stages at the moment. I'd recommend that you simply stay home for the next couple weeks and see how this plays out. If everyone sticks tight with their horses on their farm, there is a chance to contain this virus from spreading. It was recently suggested by the CSU extension folks to a tack store owner to not take in any blankets or tack for cleaning or repair, and that customers should leave their barn clothes and shoes outside the door before entering the store. That's how seriously the animal health community is taking this.

So, with all that in mind, the short answer is, it is probably best to pursue some other hobbies for the next couple weeks, ride on your property, and then see how everything is. When I suggested to stay "home," I meant that quite literally. Home at the barn. I've seen two outbreaks of this neurologic viral form over the past 27 years and it is beyond difficult to deal with a down horse that is essentially paralyzed. Hopefully this will turn out to be no more than a short-lived inconvenience while you play safe.

Dr. Nancy Loving, DVM has been both a dressage and event competitor and has been involved in the endurance world as an FEI–sanctioned veterinarian and as team vet for the USEF national endurance squad. She graduated from Colorado State University Veterinary School in 1985, and since then has practiced equine medicine and surgery exclusively.

She is the author of Go the Distance: The Complete Resource for Endurance Horses, Conformation and Performance; Veterinary Manual for the Performance Horse; and All Horse Systems Go. All Horse Systems Go contains a section on the Equine Herpesvirus, and can be found here: Horse Books Etc