Salmonella in Horses

Salmonellosis affects humans, horses, most mammals, and birds. It can cause debilitating--and even deadly--diarrhea. Salmonella bacteria can affect both foals and adults, and they spread easily by horse-to-horse contact and by fomites (shared tools, water buckets, hands, etc., on which bacteria can "hitch a ride" to the next victim). Seemingly well horses can harbor the bacteria, and when stressed, they can shed it or become ill. "The environment can be contaminated by birds, rodents, or other wild animals shedding the organism in feces, including contaminating feed for horses," says Simon Peek, DVM, MRCVS, PhD, Dipl. ACVIM, clinical assistant professor of large animal internal medicine, theriogenology, and infectious disease in the department of large animal internal medicine at the University of Wisconsin. Salmonella has received attention lately due to several outbreaks of nosocomial disease (infections picked up at a hospital by an animal that did not have that infection upon entrance) in various teaching hospitals.

Peek says there are more than 2,000 types of Salmonella, including several that affect horses. Most common is S. typhimurium, a type that also infects cattle and people. All types are zoonotic (affect animals and humans) except for one type that only infects humans.

"These Gram-negative bacteria cause a variety of problems--most commonly gastrointestinal disease and diarrhea," says Peek. "Salmonella can also cause abortion, but not as often in horses as cattle. The infection can cause septicemia; in foals it can cause generalized sepsis--bacteria in the blood spreading to multiple organs. In adult horses, bacteria are more likely to be confined to the GI tract, particularly the colon. It is much rarer in mature horses for bacteria to get out of the GI tract and into the bloodstream."

A foal with septicemia is dull and depressed, with high fever, and can die within 24 to 48 hours. Acute enteritis is the most common sign in adults, with fever and severe diarrhea. The watery diarrhea has a rotten smell and often contains mucus, and sometimes blood. Severe dehydration and toxemia occur; the animal can become very weak. Salmonella can also cause localized infections.

Shedders

"Some horses shed the organism without showing signs of disease; this is why it can become a problem at an equine hospital or referral institution," notes Peek. "A horse brought in for some other problem may be shedding bacteria in feces, perhaps intermittently."

Horses do not exhibit true carrier status, which occurs in cattle and some other animals, says Peek. He notes that certain types of Salmonella that affect species like cattle can cause an animal to be infected for life. "This does not happen in horses with the Salmonella types encountered in the U.S.," says Peek.

Most horses infected with Salmonella clear the organism from the body within days or weeks, or perhaps a few months, he notes. Yet some "silent but deadly" horses that shed the organism, but don't show any clinical signs. "They won't do that, however, for the rest of their lives," he notes.

"The sicker a horse becomes (with clinical illness), the more likely he'll be shedding the organism in large numbers," advises Peek. "If a horse is fairly healthy, he'll probably be shedding low numbers that might not be enough to cause clinical disease in another healthy horse. The problem in hospitals is that we are not dealing with healthy horses. In horses being treated with antibiotics, or that have an upset in the digestive system, or that had colic surgery, the dose of Salmonella bacteria necessary to cause clinical disease is a lot less."

The short version: If a horse's immune system is compromised when he is exposed to Salmonella, he is at higher risk.

"These horses may acquire the infection while in the hospital," says Peek. "There are also situations in which horses come down with clinical salmonellosis while in a hospital; they may have had the organism before they came in, but their immune system was strong enough to keep it at bay. Then they had colic surgery, or some other stressful procedure that allowed it to become a more rampant infection. Some hospitals and referral institutions take fecal samples for culture when a horse first comes in to identify horses with Salmonella organisms, and to protect themselves."

Hospitals sample incoming horses to find the ones shedding that could be a source of infection for other animals, and horses that are likely to get sick because they are harboring the organism in the intestines.

"Studies at teaching hospitals in the last decade show that the proportion of horses coming to equine hospitals that are shedding Salmonella in feces may be as high as one in 20," notes Peek. "In a busy hospital, that's a lot of horses; 5% of hospitalized horses appear normal, but may be shedding organisms even though they are there for a lameness, a throat surgery, or some other elective process."

This makes the problem much more complicated, and is one reason some hospitals culture horses as soon as they walk in the door, and intermittently during their stay.

Antibiotic Resistance

Peek says one concern that has recently surfaced in veterinary and human medicine is the number of Salmonella isolates that have developed multiple antibiotic resistance patterns, making them hard to treat with antibiotics. "This has raised considerable public health concerns about antibiotic use in livestock," he says.

"This has become quite controversial," Peek continues. "Our human medicine colleagues would prefer us to be extremely judicious about use of antibiotics for treating salmonella and other bacterial infections. The fear is that broad and indiscriminate use of antibiotics in animals will further promote resistance, making it more difficult to effectively treat human patients."

Spread of the Disease

Salmonella is feco-orally spread between animals by manure that contaminates feed or water. A foal might pick it up when nursing a mare or nuzzling her flank if she has lain on dirty bedding or her tail has flicked feces onto her body (if she's a shedder). A foal will also eat manure and can pick it up that way.

"Normal adult horses in a field rarely eat manure, but mares and foals often eat one another's feces," says Peek. "Thus, salmonella can be a bigger problem to control on a breeding farm. Breeders fear this disease because it can be a potentially lethal infection in foals, due to their naïve immune systems. It can get into the bloodstream and cause multiple organ failure."

Roberta Dwyer, DVM, MS, Dipl. ACVPM (epidemiology specialty) of the Gluck Equine Research Center at the University of Kentucky, says that when a farm has a salmonella outbreak, it's often little things that derail a good plan for containment. "One of the first things I ask at a farm is whether they have a rodent problem or if they feed on the ground. Mice droppings in hay or grain can be a significant source of Salmonella. Barn cats, bait, and traps are helpful, but if there's a serious mouse problem, you should contact professional rodent control people," she says.

Prevention

The best way a farm can protect against salmonella is to pay strict attention to cleanliness, prevent overcrowding, and limit possible exposure. "Getting rid of feces is important, along with isolation of animals that have diarrhea or are recovering from it," says Peek.

Dwyer says that if a horse develops diarrhea, isolate that animal immediately. "This means putting it in a stall or pen away from other horses until a diagnosis can be made or the diarrhea clears up," she says. "The exception is foal heat diarrhea, if you are sure that's what it is. Buy a box of latex gloves and wear a new pair every time you handle an animal or take its temperature."

Take care to not touch something another person might touch. "If you've been touching the sick horse and then go answer the phone, the phone is contaminated," Dwyer states. "Another person can get bacteria off the phone and go check capillary refill time on another horse, and salmonella is transmitted to that horse."

If you aren't careful about your feet, you may track bacteria (from watery feces on the ground or floor where you might not see it) to a clean area, potentially contaminating feed put on the ground or the hair coat of a horse that lies there. If that horse licks himself or a foal nuzzles a dam with a dirty flank, the disease is transmitted.

"People often move horses that were in contact with the sick one, taking them to different pens or pastures, but this is usually a big mistake," Dwyer advises. "They can be incubating the disease. There is an incubation time in which the organism is multiplying in the body, but the animal is still normal. If you move that exposed animal, you may put other horses at risk."

The ideal situation is to move the sick horse to a separate quarantine barn; only sick animals with the same disease go there, notes Dwyer. "Some big farms have a barn on the back 40 that is not used except for the occasional sick, contagious animal--and whoever takes care of the animal doesn't handle other horses," says Dwyer. After the animal is moved to the sick barn, the stall or pen it was in should be thoroughly cleaned and disinfected.

If a horse gets salmonellosis, other horses should be closely monitored. "If the one that came up positive is in a stall, get the other horses out of stalls, if possible," says Dwyer. "Even in some cases of undiagnosed foal diarrhea in Kentucky when we couldn't pinpoint the cause, we finally recommended all the mares foal outside."

If a farm has a high concentration of animals (and a lot of foot traffic, muck wagons, and hay/straw wagons going through the barn), this is a highly contaminated area in an outbreak. If other horses are currently healthy and have lived in the same pasture together, the safest place for them is on pasture, not in the barn, says Dwyer.

Keep groups together; don't mix horses that have not lived together. For a big group, put temporary fencing in the pasture they lived in, segregating them into smaller groups. If you've divided them and a horse is incubating the disease, he might potentially infect only three or four others instead of the whole herd, she explains.

"Horses should be grouped (in pasture or barn) according to age and use. All horses that go out for trail rides every weekend should be together, for instance, and not mixed with other horses," says Dwyer. "They should be in a separate pasture, away from the broodmares."

Peek is often asked how long an animal should be isolated or its feces disposed of uniquely. "Horses don't get infected with a species of Salmonella that stays there for life, but they may shed for several months," he says. "We can err on the side of caution and say six months, but most horses stop shedding within six to eight weeks."

Testing for Salmonella

You can culture and re-culture a horse to see when he stops shedding, but it won't be conclusive. You can't take a random fecal sample for culture, thinking you can give a horse a clean bill of health because that one is negative. Remember, shedding can be intermittent.

"In a hospital situation or when we're trying to prove a horse has salmonella, we take a sample every day for several days and may get one positive out of four or five attempts," says Peek. "This gets expensive and isn't always practical. It often doesn't get done on the farm, or after a horse goes home from the hospital. The client isn't going to culture every horse with diarrhea every day for several months--or wait a month and then do it every day."

Peek says PCR tests have been used to identify Salmonella DNA, but a PCR positive test does not mean the organism is alive, explains Peek. The test can identify DNA from dead organisms, which might mislead you into thinking the horse is still infective. "You might end up getting positives for a very long time."

Treatment

Antibiotics are controversial in treating salmonella, but are given to foals with documented or suspected infection because the organism more often will get beyond the GI tract and into the bloodstream.

"What's more controversial and a matter of clinician preference is whether adult horses with salmonellosis should receive antibiotics," says Peek. "If you ask 10 clinicians, there might be five who use antibiotics and five who do not. There are two things to consider. In an adult it's much less likely there will be whole bacteria in the blood (needing high levels of antibiotics to kill them, which is needed in foals). The other issue is the difficulty in giving a horse enough antibiotics systemically that the body will excrete enough of the drug into the colon to kill Salmonella organisms. You might think that by giving a drug orally (directly into the GI tract), you'd have a better chance of eradicating a Salmonella infection. But oral antibiotics may kill 'good' bacteria that ferment and digest feed. Sterilizing the gut is a bad thing in a horse."

He says on the plus side for giving antibiotics is the occasional case where whole bacteria get out of the bowel and into the blood of the adult horse. This is sometimes used as a justification for giving an antibiotic (and to kill actively replicating Salmonella within the GI tract, to lessen the damage to the gut), says Peek.

Primary treatment for a Salmonella infection is good supportive care and fluid therapy. "These horses get very dehydrated, with electrolyte and acid/base disturbances," Peek explains. "Fluid and electrolytes are crucial, along with colloids or plasma, if they need it. They lose a lot of protein through the inflamed colon. We also give strategic anti-inflammatory treatments."

Fluid is usually given intravenously to foals, and even to adult horses because the gut is often too compromised to absorb fluids given orally. "But high-volume fluid therapy in an adult horse becomes an economic issue; in any one day some of our worst cases might be given 100 liters of fluid or more," he says. "In a foal, it might be only five to 10 liters per day.

"With any cause of diarrhea, we are always fearful that the horse might develop laminitis," continues Peek. "It isn't as common in horses with salmonella as it is with Potomac horse fever, but any horse with acute diarrhea and colitis could founder," he explains. "We try to prevent this (with supportive footing and anti-inflammatory drugs such as Banamine) rather than having to treat this after the event," he explains. This type of gut infection produces endotoxemia, which always carries some risk for laminitis.

Take-Home Message

Salmonella bacteria can cause illness and even death in foals and adults. The disease is easily spread, and difficult to control and eradicate. However, good general hygiene and management techniques can help prevent problems in your horses.

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REAL-WORLD RECOMMENDATIONS:
Lessons from New Bolton Center

Biosecurity refers to all practices that reduce the chance that infectious diseases will be carried onto your farm by animals, people, or objects (such as vehicles, equipment, or feed). Biosecurity also includes practices that limit the spread of any infectious disease once it is present. Practitioners at the University of Pennsylvania's New Bolton Center in Kennett Square, Pa., have outlined several strategies to prevent infectious disease in your horse(s). Their knowledge comes not only from research and literature, but also from first-hand experience in confronting and eradicating a costly salmonellosis infection in the hospital last summer.

The cornerstone of any disease-prevention strategy is a good vaccination program. Careful management of your horse's housing and nutrition is also important, but you must consider the biosecurity of your facility. When considering how well you are protecting your animals from the risk of infectious disease, you must act on all of the following:

• Optimize housing; consider ventilation, cleanability of surfaces, and animal and human traffic patterns.
• Provide good nutrition to maintain health.
• Use antimicrobials judiciously and appropriately.
• Follow good basic hygiene and management practices. In addition to stalls and equipment, pay particular attention to the hand and foot hygiene of all personnel. Provide a place to wash hands.
• Ensure proper feed, manure, and water management; delivery of feed, water, and clean bedding; and removal of dirty bedding and manure. These procedures should be done in a manner that limits possible cross-contamination.
• Effectively choose and use cleaners and disinfectants.
• Identify animal and human traffic that represent the greatest risk to your farm and take steps to control it.
• Segregate high-risk groups such as broodmares and foals from:
  • High-traffic areas;
  • Sick animals;
  • Newly introduced animals; and
  • Animals that transiently visit your farm.
• Always use new sterile needles and syringes for all medications.
• Isolate and/or apply barrier precautions to sick animals.
• Know the source and medical history of any animals you purchase.
• Quarantine new arrivals.

If you take these steps and work with your veterinarian, you will minimize your risk of problems with salmonellosis.

Editor's Note: Information provided by New Bolton Center.

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FOAL IMMUNITY

Foals don't get much protection from salmonella via colostrum, says Simon Peek, DVM, MRCVS, PhD, Dipl. ACVIM, clinical assistant professor of large animal internal medicine, theriogenology, and infectious disease in the department of large animal internal medicine at the University of Wisconsin. "The mare creates antibodies, but protection against salmonella is complicated--a combination of what's called humoral and cell mediated--and is not as straightforward as just antibodies that may be present in colostrum," he explained. "Salmonella is an organism that, when in a host, is within the cells. Antibody alone does not do a comprehensive job of getting rid of it. You need white blood cells to do their job, too. So, it's a bit different than some other infectious diseases where protection may be conferred more completely by antibodies contained in colostrum. The organism is similar to Rhodococcus equi in this respect. It tends to hide within the tissues of the intestinal tract, where it's very difficult for antibody to get to it."

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PREVENTING FURTHER INFECTION:
Disinfecting After a Sick Horse

When a horse is diagnosed with salmonellosis, the first thing is to treat him, of course. But following very closely on the heels of that is preventing infection of other horses (and people) on the property. To the fullest extent possible, stalls, trailers, and equipment should be disinfected.

Stalls/Equipment--Roberta Dwyer, DVM, MS, Dipl. ACVPM (epidemiology specialty) of the Gluck Equine Research Center at the University of Kentucky says the worst cases are dirt floors and raw wood stalls.

"This is a challenging situation, because disinfectants safe to use around horses don't work on dirt," she says. "My recommendation, if it's not feasible to dig up the first eight to 12 inches of dirt, sand, or clay (to replace with new material after the outbreak) is to completely muck out the stall and let it dry completely. You can use fans on very low settings to help dry the floor. You don't want strong air movement or the bacteria may aerosolize (become airborne). Gentle air movement will hasten drying, as well as sprinkling barn lime on damp spots."

As far as walls and other surfaces go, cleaning before disinfecting is paramount; disinfectants don't work well in the presence of organic matter like dirt and feces. But pressure washing could be dangerous as any bacteria present could aerosolize; stick to hard scrubbing.

If a barn has raw wood stalls, Dwyer recommends cleaning with a disinfectant, then painting them with two coats of polyurethane or marine-quality varnish to seal the wood. "This is best to do in the summer when the stalls can be really dry," Dwyer advises. "You might have to do some caulking on knots and holes, but this will make a much easier surface to clean if you ever have to do it again.

"Any buckets or hay feeders in stalls also need to be cleaned with disinfectant, rinsed, then soaked in a disinfectant solution for 10 minutes," she adds. "Always rinse anything the horse eats or drinks out of with clean water several times and allow it to dry."

Trailer--A trailer might be the weak link in your defense plan, says Dwyer. If you haul a sick horse to a hospital, the trailer should be thoroughly cleaned and disinfected before hauling another horse. "Most people muck it out, but just cleaning out the manure is not enough. The inside should be scrubbed with detergent and rinsed. Then apply disinfectant and let it dry."

The shovel and fork used to clean out a trailer are also contaminated. These must be cleaned with a detergent, rinsed, and soaked in disinfectant for 10 minutes.

Pasture--It's almost impossible to "disinfect" a pasture where sick horses contaminate forage and ground. "That would adversely affect soil and grass, and raise environmental issues," says Dwyer. "Anything you could put in a pasture that would kill Salmonella in the soil would kill everything--all the beneficial micro-organisms." In one contamination situation, she recommended giving the pasture time to dry out, then chain harrowing the dry pasture to break up manure and expose more of it to sunlight and drying. She also recommended not putting horses on the pasture for two months.

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HYGIENE PROTECTS HORSES AND PEOPLE

If you are in the midst of an outbreak or dealing with any potentially contagious disease, there is great benefit in having hot and cold water available in the barn or tack room, and liquid soap in a pump dispenser for cleaning hands after caring for a horse. "Don't use bar soap; it becomes quite dirty after use," says Roberta Dwyer, DVM, MS, Dipl. ACVPM (epidemiology specialty) of the Gluck Equine Research Center at the University of Kentucky. "No one wants to touch it. Liquid pump soap is safer and need not be antibacterial. Regular soap is very effective for cleaning dirt off your hands. Use disposable paper towels for drying hands, so no one ever has to touch a towel someone else has used.

"Any of the hand disinfectant products are useful if they are 62-65% ethyl alcohol," continues Dwyer. "I also like the foams. These have been shown to work in human hospitals. You can use the gel or foam on clean hands (already washed), not these covered with manure or dirt. This not only protects the next horse you touch, but also yourself and other people you may contact.

"In most of the salmonella outbreaks in veterinary hospitals, people usually don't get sick because they are highly aware of the dangers and take precautions," notes Dwyer. "Do not allow children in a barn where there is a known salmonella case, and make sure your hands are clean before you go home to take care of children."

A sick horse in isolation should have limited contact with people. "The only people that should have access to that animal are the farm manager, horse owner, and essential workers," states Dwyer. "These people should be aware that salmonellosis can be transmitted to humans. Any individuals who are pregnant or immuno-compromised due to cancer, immune diseases, or other issues are at risk of infection with a zoonotic disease."

~~ BACK TO TOP ~~

One day you notice something amiss in your horse--a little clumsiness in his gaits, a subtle lack of coordination. He's not lame, but something's not right. You suspect equine protozoal myeloencephalitis (EPM), the leading diagnosed cause of neurologic problems in North American horses. Should you get a veterinarian out? Absolutely! But be prepared. You could be facing a case of Wobbler Syndrome rather than EPM.

DR. ROBIN PETERSON ILLUSTRATION

Compression of the spinal cord, whether because of misaligned or malformed vertebrae or some other problem, causes the distinctive "wobble" of Wobbler Syndrome. This compression injures or kills the nerves that are responsible for sensing the position of the limbs. This, of course, leads to the lack of awareness that causes clumsiness and incoordination.

Many diseases and disorders display signs similar to EPM, and, says Bill Bernard, DVM, Dipl. ACVIM, of Rood and Riddle Equine Hospital in Lexington, Ky., "There are probably more horses out there with Wobbler than EPM."  In fact, according to some statistics, EPM is present in only 1% of the country's equine population.

To help you understand the differences between wobbler and EPM, we turned to Bernard, as well as Stephen Reed, DVM, Dipl. ACVIM, of The Ohio State University Veterinary Teaching Hospital, and Martin Furr, DVM, PhD, Dipl. ACVIM, associate professor at Virginia Tech University's Marion duPont Scott Equine Medical Center. They detail in this article the causes, treatments, and likely outcomes of wobbler syndrome.

Mixed Signals

Wobbler, also known as wobbles, takes its name from its primary sign--a wobbling or uncoordinated gait. In technical terms, the horse has a "proprioceptiveness deficit," or a lack of physical awareness of his limbs and their placement. More simply put, says Reed, "Wobbler horses don't know where their feet are." This leads to clumsiness and general incoordination (ataxia) of the limbs.

The disease can become so severe that the horse crashes into things or can't stand up. However, Reed says, that's not common. "We score neurological signs on a scale of zero to five, where five is recumbent (laying down)," he explains. "A lot of horses that we see start at a grade two--everyone can see they're clumsy--then progress to a three or four."

The signs can develop gradually or, as Bernard notes, "The horse can be normal one day and severely abnormal the next day." In addition, the signs might be seen only in the hind limbs, or could affect all four limbs. As a general rule, though, the unsteadiness is symmetrical, affecting right and left sides to an equal degree.

This is a distinction from EPM, in which Furr says, "There is usually a degree of asymmetry, although EPM can be symmetrical sometimes." In addition, EPM-afflicted horses might exhibit muscle wasting (atrophy), cranial nerve signs (such as facial nerve paralysis), and behavioral changes. None of these are signs of wobblers.

However, the vets emphasize, not every EPM horse exhibits all of these signs. As Reed explains, "If the horse does show atrophy and asymmetry, there's a much higher chance of EPM. When those things are absent, however, a lot of wobbler horses can look an awful lot like an EPM horse."

A definitive distinction between the two requires pursuing diagnostic avenues beyond a thorough neurological exam, as we'll discuss later.

Why Do They Wobble?

Compression of the spinal cord causes the distinctive "wobble" of Wobbler Syndrome. Furr explains, "Compression injures or kills the nerves that are responsible for sensing the position of the limbs." This, of course, leads to the lack of awareness that causes clumsiness and incoordination.

A number of factors can cause compression, says Furr. In general, all of them relate to stenosis (narrowing) of the vertebral canal, which reduces the space around the spinal cord and thus creates pressure. Sometimes this occurs when bone surrounding the spinal cord grows incorrectly due to instability or arthritis. In other cases, instability or weakness of the joints can cause hypertrophy, or excessive growth, of the ligaments inside the canal. Malformed or misaligned vertebrae, soft tissue inflammation around the vertebrae, or an "outpouching" of the joint capsule into the canal can also squeeze the spinal cord. Or the spinal cord itself can become inflamed.

Horses at Risk

For reasons that research has not yet uncovered, certain horses seem predisposed to wobbler syndrome, or are at least statistically at greater risk of developing the disorder. Male horses, for instance, are twice as likely as females to suffer from wobbler. Larger, faster-growing individuals and breeds (notably Thoroughbreds, warmbloods, and Quarter Horses) also seem to be affected more often.

Furr notes that signs can often crop up around age two, when the horse begins training. However, the syndrome can be seen in all ages, and Barrie Grant, DVM, Dipl. ACVS, of San Luis Rey Equine Hospital in California, says he operates on twice as many horses older than five years of age than younger horses. When the problem affects older horses, it is usually because of arthritis, says Bernard.

In addition, notes Furr, diet, activity, and conformation are "all potential contributors, but not much research has been done to evaluate them." Micronutrient nutrition--known to impact degenerative joint disease--might play a part, as might high-energy (a.k.a., high-carbohydrate) diets and copper deficiency.

All three vets agree that there also seems to be a strong genetic component to wobbler syndrome. "The horse doesn't necessarily inherit the disease," Furr explains, "but he may inherit traits that increase the likelihood of getting it, if other risk factors are encountered."

These might include how big a horse grows, how wide his vertebral canal is, and how big his vertebrae are. So, for example, a horse born with a narrow vertebral canal might develop wobbler from a case of arthritis that wouldn't trigger the syndrome in a horse with a wider canal, says Reed.

In short, says Furr, "This is probably a multifactorial disease, meaning that many different things have to happen in one individual to result in the condition."

Identifying the Disorder

If you suspect your horse has wobbler, the first thing you'll do is call your veterinarian to conduct a thorough physical and neurological exam. This, says Reed, should achieve "anatomical localization" or help the vet find where the problem is centered. For instance, he continues, "If there is no evidence from the exam of problems in the brain, the brain stem, or the cranial nerve, but there is evidence of gait ataxia or proprioceptiveness deficit, then we know the problem is in the spinal cord, and we know it's in the neck."

The next step is to take simple radiographs of the neck bones. These images can be extremely valuable in helping the vet pinpoint the location and cause of signs.

Reed notes that at The Ohio State University they take measurements off of the radiograph to assist in diagnosis. "We find that if the width of the vertebral canal is less than half the width of the vertebral body, we have an 80% probability that the horse is a true wobbler," he explains.

If radiographic evidence isn't strong enough, the veterinarian will follow up with a myelogram. This procedure--in which dye is injected into the spinal canal and another set of radiographs is taken--is the only way to definitively identify wobbler syndrome. But it requires general anesthesia for the horse, so it involves a certain amount of risk and expense.

In some cases--especially with horses under two years of age--veterinarians might recommend holding off on this pricy step. Horses of this age, says Bernard, "are still growing, they're clumsy, but they're not necessarily neurological. If signs are mild, we may decide that the myelogram isn't necessary. We may suggest just watching the horse for three or four months because sometimes, if a young horse is a grade one or two, he may grow out of it in time."

On the other hand, if you're considering surgery (which we'll discuss later), you will want a myelogram done since it clearly shows the compression site.

One point to note, says Bernard, is that a myelogram can't rule out all other disorders that might occur simultaneously with wobbler. For instance, a positive wobbler diagnosis does not mean the horse is free of EPM, since a horse can have both disorders (although that's rare). So, Bernard encourages owners to ask veterinarians to check for both conditions.

Non-Surgical Treatments

Don't despair if your horse is diagnosed with wobbler syndrome. As Reed says, "Neurological is not a euphemism for necropsy (postmortem exam). There are many things you can do to treat the horse and allow him to have a long, successful life."

Some options are non-surgical. If you see the problem in a fast-growing weanling, for instance, correction could just mean modifying the youngster's diet to slow his growth rate, says Reed. "That can allow for remodeling of the vertebrae to increase the size of the canal. Then, with corticosteroids, rest, and turnout in a small paddock, some will stabilize," he adds.

Reed believes in the benefits of vitamin E supplements and recommends them for "every horse with neurological signs." He says trauma can cause substantial oxidative damage to the nerve tracts, which vitamin E, an antioxidant, can help repair.

"Vitamin E will help equine degenerative myelopathy and equine motor neuron disease, and I think it will help with EPM and wobbler, too," he says.

Non-surgical treatments come with their share of controversy, though. Bernard cautions that some "wobbler" horses which have recovered over time without operations might not actually have had the syndrome, but simply might have been experiencing a clumsy growth stage. If a myelogram was never done, he says, you can't know for sure that the horse truly had wobbler syndrome.

Reed notes that in a study he and some colleagues performed, only 10% of horses with wobbler syndrome became normal given nothing but time and rest. On the other hand, when surgery was performed, about 70% of the patients improved.

Surgical Options

If you do opt for surgery--which Furr calls "the only specific treatment" for wobbler--you probably will have two choices. The first, a dorsal laminectomy, involves actually removing portions of bone from the spine. Reed notes that this procedure is generally an option only if the lesion (the compression site) is static. In other words, "The cord remains pinched no matter what position the neck is in." (The vet can generally determine this from the myelogram.)

The good thing about laminectomy is that it provides instant relief from pressure. However, Reed adds, "We have found that, in our hands, this procedure is so traumatic, many horses don't come out of it well. Some are not able to get up." So his practice performs only the other, most common, type of surgery called cervical stabilization.

In this procedure, explains Furr, "The affected joint is fused with a metal insert. This minimizes the mobility and instability of the joint, and the bone and ligaments which are compressing the cord will remodel, decrease in size, and relieve the compression." Reed explains that the theory behind this is that bone grows due to movement. "If you stop the motion, the bone will atrophy, and that leads to decompression," he says.

Stabilization can take weeks or months to show an impact, with total recuperation and rehabilitation taking up to a year. However, Reed notes that follow-up myelograms have shown significant improvement as soon as eight weeks after the surgery. And, he continues, "As long as the horse is stabilized, and he can get up and down, we believe that vertebral stabilization success rate is higher and the complications--especially those associated with death--are pretty low."

In fact, Reed says that after performing about 160 cervical stabilization surgeries, about 75% of patients showed significant improvement. "We may even get near 80%," Reed says. "And 62% are becoming athletic, whereas it used to be only 50%."

What's deemed athletic? Reed mentions two Thoroughbreds treated for wobbler by himself and a colleague. "They went off as first and second favorites in a race at Santa Anita, and later finished 1-2 in a race," he recalls. And, he adds, the treatment is long-lasting. A horse treated in 1973 went on to careers in racing and jumping, "And now, 15 years after the surgery, he's still being ridden," Reed states.

But even Reed doesn't believe that surgery is always the answer. For instance, he says, "If there are three sites of compression, we find a low probability of the horses coming back and doing well. One horse we operated on is strictly at pet status." The owners, he says, have to ask if they are in a financial position to do the surgery and be able to accept the horse as a pasture pet if it cannot regain athletic ability.

Bernard feels even more strongly about the potential negatives of surgery. "Surgery is not a panacea. It may not be the answer," he cautions. "Surgeons who do a lot of this surgery tend to say that it may improve the horse by one to two grades. So, if a horse is grade three, and you get it to a one, which is mild, maybe then it's worth it. However, the horse may not improve at all or only a little bit."

And since the cost of surgery and recuperation can run from $3,000 to $8,000, owners must weigh statistics and probable outcomes against personal finances and emotional attachment.

Doing Your Part

The good news is that you do have some control over the operation's success and your horse's recovery. First, you can help by having the surgery done soon--ideally within 30 days of diagnosis, recommends Reed. After the operation, he continues, patience and persistence pay off. "We find that horses do best when they have owners who don't give up," he states.

For example, don't fret if your horse looks the same 60 days post-surgery as he did before the operation. That's normal. In fact, says Reed, owners should expect only glimmers of change in patients over the next six months or so, starting with small improvements after 90 days, then moderate improvements after 180 days. Continued improvements occur as the horse develops fitness and continues to heal.

Reed believes that active rehabilitation once the horse has stabilized is a vital part of recovery. "I push ground work," he says. "Walking over ground poles and cavaletti, trotting up and down hills and, eventually, putting weight on the horse's back again. Then, over time, putting the horse back to work."

Obviously, Reed believes that many wobbler patients can return to normal use. But he cautions that some veterinary neurologists disagree, advising against riding any horse that's been diagnosed with neurological signs, even if he's been treated. They fear that the wobbler disorder might have caused permanent damage to the spinal cord. And, he admits, "At necropsy, we do see some nerve tracts drop out. But I think you'd probably see that on me, too. The key is safety. There is not a horse made that's worth getting a person hurt over."

Bernard notes that often a veterinarian can't recommend riding a horse with neurological signs for liability reasons. And a horse showing grade three neurological signs, he adds, probably is not safe to ride. But he continues, "people should use their own discretion" when determining risks--to themselves and the horse--of riding their own wobbler or recovered wobbler.

If you do opt to ride, use common sense. Evaluate the horse's abilities before you get on. If he seems only mildly affected, you might consider riding him at a walk on solid, level ground. As time passes, continue to evaluate his way of going and his balance, gradually progressing to more challenging work such as trotting, walking over ground poles, etc., if it seems safe.

The fact is, there's no guarantee that a former wobbler will recover enough to make a reliable mount again. But there's no question that, with treatment, time, and a dedicated and patient owner, many horses do make that turnaround.

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SAVING SEATTLE SLEW

One of the pioneers in the spine stabilization technique is Barrie Grant, DVM, Dipl. ACVS, of San Luis Rey Equine Hospital in California. Along with Pamela Wagner, DVM, MS, MD, and George Bagby, MD, he adapted a procedure from the Cloward technique, used since the 1950s for fusing vertebrae in human patients. They first performed the procedure in a horse in 1977 and developed the "Bagby basket" for fusing equine vertebrae in the early 80s. Although Grant has done this procedure on hundreds of horses over the years, his most famous patient received an implant in April of 2000. Thoroughbred champion Seattle Slew had begun having problems covering mares in the breeding shed that spring because of hind limb incoordination. Conservative treatment yielded only temporary improvement, and a myelogram showed spinal cord compression from arthritic vertebral facets. Grant and Bagby developed a new threaded basket, appropriately named the "Seattle Slew Basket," for the procedure.

Grant and a team of surgeons implanted the basket on April 2, 2000. After an extended recuperation period, Seattle Slew recovered his previous form in the breeding shed, getting more than 50 mares in foal in 2001. The procedure was repeated a second time in 2002, when Grant and colleagues placed a second basket. The surgery was successful; however, Seattle Slew passed away later that year.

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GLOSSARY

Ataxia--Loss of muscular coordination, especially in the limbs.

Asymmetry vs. symmetry--Simply put, when something has symmetry, it is the same on both sides; when it is asymmetrical, it is not the same on both sides. For instance, while a wobbler horse might show equal incoordination on left and right sides, an EPM-affected horse might show incoordination only on the left or the right side.

Atrophy--Degeneration or wasting away of part of the body, often from disuse; in some EPM cases, the horse's muscles atrophy.

Bagby basket--A small basket-like device for fusing equine vertebrae, developed by Barrie Grant, DVM, Dipl. ACVS, Pamela Wagner, DVM, MS, MD, and George Bagby, MD, in the early 80s. They first performed a procedure for equine spinal stabilization in 1977, adapting a technique used in human medicine.

Cervical compressive myelopathy--Literally translated, this means a disorder of the spinal cord in the neck due to compression. It's a more technical name for wobbler syndrome.

Cervical stabilization--Also known as vertebral stabilization, this is the most common surgical procedure for wobbler horses. It involves fusing the affected vertebrae with a metal insert.

Cervical vertebral instability--This has been used as a name for wobbler syndrome. However, since instability is not always a factor in wobbler, this is no longer considered a good descriptor.

Cervical vertebral malformation--Literally, this means a malformation of the bones in the neck. Again, it has been used to describe wobbler, but is not an accurate term since it does not mean the spinal cord is compressed. Without compression, there is no wobbler syndrome.

Dorsal laminectomy--A lesser-used surgery for wobbler syndrome, it involves removing part of a vertebra.

Myelogram--A diagnostic tool that involves injecting dye into the spinal canal and taking radiographs. The resulting film shows an outline of the spinal cord, helping the vet pinpoint the location(s) of compression and determine whether the compression is caused by enlargement of the cord or narrowing of the spinal canal.

Proprioceptiveness deficit--Literally, a lack of body position awareness. Proprioceptors are sensory nerve endings that tell you where parts of your body are.

Stenosis--Narrowing of a passageway in the body. When discussing wobbler syndrome, it relates to narrowing of the vertebral canal.

Vertebral canal--Also known as the spinal canal, this is the "tunnel" through the vertebrae in which the spinal cord is located.

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A veterinarian can say several things that will chill every horse owner's heart, including colic, laminitis, navicular disease, and wobbler syndrome. These cause fear because of the unknown--and often unfavorable--outcome for your horse. But as veterinary medicine progresses, these terms cause less anxiety because some of the unknowns are being solved. A case in point is a horse affected with wobbler syndrome.

Clinical Signs

A wobbler is a horse with a damaged spinal cord. The major causes of spinal cord  damage include malformation of the cervical (neck) vertebrae, trauma to the vertebrae, proliferation (excessive growth) of surrounding soft tissue, or damage by viruses, protozoa (as with equine protozoal myeloencephalitis, or EPM) or parasites. The most obvious clinical sign is a horse which presents with an abnormal gait characterized by wobbling (he looks like he has had a fair amount of tranquilizers). Mild cases might only demonstrate an inability to change leads or stop smoothly, or a negative change in behavior that results in poor performance. The mild cases are often confused with subtle problems of the hind legs, especially of the hock and stifle.

The hind limbs are affected because the nerves that supply the area are located on the outside of the spinal cord in the cervical area and therefore are more easily damaged than nerves leading to the front limbs, which are protected deep within the spinal cord.

Diagnosis

Since other conditions can mimic wobbler syndrome, it's important to obtain a complete diagnosis to facilitate treatment and improve the long-term prognosis. Clinical diagnosis usually requires a complete neurological exam, radiographs of the skull and cervical area, a myelogram, and cerebral spinal fluid testing.

A veterinarian experienced in observing neurological deficits should perform the neurological exam. The exam might include procedures to assess back withdrawal, tail and anal tone, panniculus (skin sensation, mobility of the neck, limb placement, tail sway, position of the body and limbs when walked in tight circles and up and down hills, and observation of natural gaits during free exercise.

If the neurological exam suggests that the cervical area might be the source of the problem, a series of radiographs (X rays) are taken with the horse lightly sedated. The radiographs are then examined for fractures, collapsed intervertebral disc space, misalignments, narrowed spinal canal measurements, and arthritic articular (joint surface) facets.

Depending on the examination findings, a myelogram will be used for a more complete diagnosis. The horse is placed under general anesthesia, cerebrospinal fluid is withdrawn for analysis, and an iodine-based fluid is placed in the spinal canal to outline the spinal cord on radiographs. The spinal fluid is examined for increases in white cells that might indicate an infection, for unusual cells that might be seen with a neoplastic (cancer) condition, and for the presence of antibodies for herpesvirus or protozoa (Sarcocystis neurona, the organism that causes EPM).

In summary, if your horse presents with neurological signs of lameness, it will be important to enlist the help of your veterinarian for diagnosis. Recognizing early signs of any disease and seeking veterinary expertise will help increase your horse's chances of successful treatment and recovery.

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