Showing posts with label EQUUS Magazine. Show all posts
Showing posts with label EQUUS Magazine. Show all posts

Thursday, November 7, 2019

Encouraging findings about long-distance transport

New research shows that horses transported long distances with a commercial shipping company had low risk of associated health problems.


A large-scale study of horses transported long distances with a commercial shipping company found a low risk of associated health problems.


Previously, much of the data on equine travel risks was gathered using horses bound to slaughter facilities, which the researchers say is not applicable to horses transported for other reasons.

“You cannot transfer the findings from papers on the transport of slaughter horses to the transportation of sport horses because the vehicles are completely different,” explains Barbara Padalino, DVM, who conducted the study as part of her doctoral work under the supervision of Gary Muscatello, BVSc, PhD, at the University of Sydney. “Slaughter-bound horses usually don’t travel in single stalls. They are transported in higher density, and often these horses are not tamed and have no travel experience.”

To gather data more reflective of sport and pleasure horses, Padalino and fellow researchers reviewed the records of a commercial transportation company that regularly moves horses between the east and west coasts of Australia. Information was provided on all 1,650 horses the company transported along the same route from April 2013 to April 2015.

“The trip consisted of four stages,” says Padalino. “Sydney to Melbourne [10 hours], Melbourne to Adelaide [eight and a half hours], Adelaide to Kalgoorlie [24 hours] and Kalgoorlie to Perth [six hours]. After each stage, horses were given a 12-hour rest period. The total duration of travel was approximately 85 hours with approximately 49 hours in transit and 36 hours for rest stops.”

At the collection stable and rest points, horses were individually housed in walk-out rubber-lined stables and/or paddocks that were used only for horses in transit. Padalino adds that the transportation company was well-respected and well-run, following guidelines provided by the Australian code of livestock transportation.

The data showed that 97.2 percent of the horses arrived at their destination with no signs of disease or injury. Among the few horses who did have problems, the most common were respiratory illness (27 percent), gastrointestinal issues (27 percent), fever (19 percent) and injuries (15 percent). There were four transportation-related deaths, making the overall death rate .24 percent.

Horses were more likely to hurt themselves in the early hours of the trip. “Injuries are often associated with misbehaviors, such as refusing to load or kicking in the truck,” says Padalino. “It’s been reported that the first hour of a journey is always the most stressful for horses. During that time horses tend to move more, try to escape more and lose their balance more.”

In addition, the researchers found that horses transported in the spring were more likely to develop gastrointestinal or respiratory problems. This, they say, may reflect higher temperatures at a time when many horses still have winter coats, or challenges posed to their immune systems by hormonal fluctuations or increases in pollen or other allergens associated with the season.

Padalino says this low illness and injury rate is encouraging. “This percentage is actually really good, considering that we examined one of the longest journeys which horses can do worldwide in a very hot country. This figure tells us that safe transportation of horses is possible when done by experienced people.”

For trips of more than 20 hours, she recommends using a reputable shipping company, inspecting the transport vehicle and having a full veterinary exam performed ahead of time to identify any subclinical illnesses that the stress of transportation may exacerbate.

Reference: “Health problems and risk factors associated with long haul transport of horses in Australia,” Animals, December 2015

Thursday, September 19, 2019

7 Things you may not have known about DMSO

This odiferous compound has become a common treatment for a variety of inflammatory conditions. Here are a few interesting facts about DMSO's history and action.

Two decades ago, if you mentioned dimethyl sulfoxide (DMSO) around the barn you may have gotten puzzled looks in response. Back then, this industrial solvent turned anti- inflammatory therapy was relatively new to the horse world, and even if people had heard of it they viewed it as an unusual or even mysterious option.Since then, DMSO has gone mainstream. It is approved by the Food and Drug Administration (FDA) for topical use on horses, but veterinarians regularly use the chemical “off-label” in other ways to treat a wide array of inflammatory conditions, from laminitis to neurological problems. When the DMSO’s distinctive garlicky smell wafts through the barn these days, people are more likely to nod knowingly than wonder what’s going on.

Nonetheless, DMSO is a little like aspirin---something that many people use without necessarily thinking too much about how it works. But learning more about DMSO may help you appreciate how it can be useful in maintaining your horse’s health and comfort. So here are seven things you might not know about DMSO.

1. The therapeutic properties of DMSO were discovered more or less by accident.

A byproduct of paper production, DMSO was first developed as an industrial solvent. As people worked with the chemical, they noticed that if they spilled a bit of DMSO on their hands a distinct garlicky taste would be on their tongue shortly thereafter. This intrigued chemists, who began researching how the liquid could so quickly pass through skin and mucosa, but the work was generally limited to exploring non-medical applications.

Then, in the 1960s, Stanley Jacob, MD, began investigating DMSO as a preservative for organs destined for transplants. Work done in his laboratory soon sparked a rush of research into DMSO’s possible medical uses.

By 1965, however, the FDA closed down clinical trials citing safety concerns. Since then, DMSO has been approved for some specific applications. In human medicine, these include use as an organ preservative and as treatment for a bladder disease called interstitial cystitis. In 1970 it was approved for topical use in horses and dogs.

2. DMSO’s anti-inflammatory properties come primarily from its antioxidant action.

DMSO is classified as a nonsteroi- -dal anti-inflammatory drug (NSAID), just like phenylbutazone (“bute”). Unlike bute, however, DMSO controls inflammation primarily by acting as an antioxidant.

You may be more familiar with anti-oxidant sources in nutrition, such as vitamin E or lycopene, but DMSO has a molecular structure that allows it to function in the same way. Specifically, DMSO binds with “free radicals,” which are oxygen compounds---leftovers from normal biochemical reactions---that damage or destroy healthy cells. These free radicals are often the byproduct of inflammation and, in turn, cause more swelling and inflammation as they accumulate. DMSO is a free radical scavenger that slows or halts this process.

When used to control inflammation in strains and other soft-tissue injuries, DMSO is usually applied topically. However, it may also be injected into a target area when an injury occurs in particularly dense tissue, such as a bowed tendon, or the site is difficult to reach. A veterinarian may administer DMSO orally or intravenously in the early stages of laminitis to try to slow or halt the inflammatory cascade.

3. DMSO draws fluid from tissues.

DMSO is a hygroscopic compound, meaning it attracts water. This property makes the compound especially versatile. For instance, it can reduce edema0 in swollen limbs and is often used as part of a “sweat” to combat stocking up. DMSO can also reduce swelling in the brain and spinal cord, which can be literally lifesaving in diseases like West0 Nile encephalitis. DMSO may be used to draw fluids out of the lungs in cases of acute pulmonary edema.

Because it pulls water from tissues, DMSO has a diuretic effect, meaning it makes a horse urinate more. This can help flush toxins from the body more quickly. With this action in mind, DMSO is often given intravenously in the treatment of cantharidin poisoning (blister beetle toxicity), to lessen the effect of the toxin on the kidneys and intestinal tract. After episodes of tying up, DMSO may help horses eliminate waste products of muscle breakdown through their urine more quickly. The diuretic action of DMSO, however, can make it unsafe for horses who are dehydrated or in shock. It can further dehydrate these animals or dangerously lower their blood pressure.

4. DMSO can carry other substances through the skin.

DMSO’s molecular structure allows many substances to dissolve completely within it. It also allows the chemical to transport these dissolved substances through cell membranes without damaging them, even if these sub- stances wouldn’t be able to pass through on their own.

For instance, treating rainrot or other skin infections can be difficult because the responsible organisms are buried deep under the skin or crusty, painful scabs. However, a mixture combining antibacterial medication with DMSO can pass through the skin and reach the affected area. For the same reason, DMSO is often added to antifungal medications for treatment of eye conditions and sometimes to steroids for targeted, topical anti-inflammatory treatment.

It’s important, of course, to avoid inadvertently mixing DMSO with potentially toxic substances. You wouldn’t want fly spray crossing into your horse’s bloodstream, for example, so take care to avoid applying DMSO to your horse if he has recently been sprayed. Likewise, avoid mixing DMSO with substances that could be toxic if ingested, such as organophosphates or mercury salt. Also be mindful that the effects of some drugs, such as corticosteroids and atropine, are intensified when mixed with DMSO, so doing so needs to be done with caution under a veterinarian’s direction.

5. DMSO may provide pain relief on its own.

Although it’s commonly mixed with compounds to provide pain relief, some studies suggest that DMSO alone has analgesic properties. Research shows that DMSO slows or blocks conduction of impulses along nerve cells, which in effect reduces pain from musculoskeletal injuries, postoperative incisions and other sources. Relief is only temporary ---lasting up to a few hours---because as the DMSO dissipates, normal nerve function returns. It can be combined with other pain-relieving drugs, however, to extend the analgesic action.

If it seems like DMSO has a variety of purported actions, that’s true. It’s nothing if not versatile. Some applications of DMSO combine all of these: For instance, it is often used in surgical colic cases to reduce the risk of tissue adhesions due to inflammation and poor circulation; some surgeons think that it may also provide some pain relief in the hours following surgery.

6. DMSO is a prohibited substance in some sports.

DMSO isn’t technically a medica- tion, but various competition organizations treat it as one when it comes to drug testing.

The Fédération Equestre Internationale (FEI) classifies DMSO as a “controlled” prohibited substance, meaning that although it may have some therapeutic value, DMSO has the potential to affect a horse’s performance and its use is forbidden or limited. As of January 2018, the threshold of DMSO allowed by FEI was 15 micrograms per milliliter in urine or one microgram per milliliter in plasma. The Jockey Club allows 10 micrograms per milliliter of plasma. If you compete with your horse, check any governing association rules regarding DMSO use.

Also keep in mind that because DMSO can move other materials through the skin, combining it with other medications could result in a violation of thresholds for both. For instance, mixing DMSO with the topical NSAID Surpass (diclofenac) can cause an increase of the medication in the bloodstream, leading to a disqualifying test. The medication guidelines for the United States Equestrian Federation state, “Do not apply diclofenac cream in combination with any other topical preparations including DMSO, nitrofurazone, or liniments.”

7. DMSO use in horses hasn’t been studied extensively.

A search of a research database will turn up a good sampling of peer-reviewed papers on DMSO use in horses, but the compound has gotten far less scientific scrutiny than have medications developed specifically for therapeutic applications. Some studies about DMSO’s effects contradict each other, particularly in regard to its use for treating arthritis.

Scant information is available regarding dosing. Often veterinarians rely on their own experiences and those of their colleagues in deciding when and how to use DMSO. That is why it’s important to let your veterinarian lead the way when it comes to treating your horse with this compound.

Whether applied topically, orally, intravenously or by injection, DMSO requires careful handling. But its versatility means that if you haven’t used it so far, you probably will eventually. If you do, keep these basic facts in mind to make sure your horse benefits fully from this unusual preparation.




Sunday, July 7, 2019

What to do when your horse has a fever

What to do when your horse has a fever

When your horse’s temperature climbs, it may be best to simply let the process run its course. But sometimes you’ll want to get a veterinarian in right away. Here's what you need to know about fever.

You’ve been keeping tabs on your horse as you’ve gone about your barn chores, but something’s not quite right. Normally, he’s never far from his buddy, and he’d be ranging around his paddock looking for the best bites of grass. Today, however, he’s spent most of his time hanging in the shady corner by himself. He seems normal enough when you bring him in, but as you’re grooming, you get out the thermometer. That’s when you really start to wonder what’s up: His temperature is just topping 102 degrees Fahrenheit.


You know that’s a little high---you’ve been in the habit of checking your horse’s temperature once or twice a month, and it’s always been about 100 degrees---but what do a couple more degrees really mean?

“There are several reasons why horses can have an increased body temperature that would not be a fever,” says Rose Nolen-Walston, DVM, DACVIM, of the University of Pennsylvania. “So the first question to ask when you take a horse’s rectal temperature and it is high is, ‘Is this a fever or not?’”

A “normal” body temperature for individual horses can vary, from about 98 to 101 degrees Fahrenheit, with 100 being average. But it’s also normal for a horse’s body tempera-ture to fluctuate during the day. It may be somewhat higher in the evenings than in the mornings, for example, and it is likely to rise naturally on hotter days or after exercise. A mare’s temperature may rise and fall during different stages of estrus. All of these fluctuations are temporary.

“If you ride your horse and work him hard on a hot day, his temperature rises, but this is called hyperthermia rather than a fever,” says Nolen-Walston. “The main causes of hyperthermia include exercise, extreme heat and humidity, and anhidrosis [an inability to sweat].” Allowing him to rest and drink---and perhaps hosing him down with cool water---ought to bring his temperature down to normal within a half hour or so.

If, however, your horse’s temperature remains elevated with no obvious cause, then it’s time to investigate the reasons why. “Most of the time, if a resting horse has an increased rectal temperature it’s because he has a fever,” says Nolen-Walston.

Rise in body temperature is one of the first and most easily recognized signs of many illnesses, and it is part of the immune system’s defense against infection. “Fever is a response by the body---along with inflammatory processes---to try to combat pathogens by stimulating molecules to speed up healing processes,” says Katherine Wilson, DVM, DACVIM, of the Virginia–Maryland Regional College of Veterinary Medicine.

The best course of action when a horse has a fever can vary. How high his temperature is, and how long it lasts, can help you decide whether it’s best to let a fever run its course---or to call in a veterinarian right away. Here’s a look at how fevers work and how veterinarians suggest you handle them.

How Fever Works

Fever is related to the body’s internal temperature regulation system, which is controlled by the hypothalamus. A small structure at the base of the brain, the hypothalamus receives sensory input from sensors in the central nervous system that monitor the heat of
the blood as it circulates through the brain, as well as from nerves that detect temperatures near the surface of the skin. This gives the hypothalamus information about both internal and external temperatures.

“The hypothalamus determines the body’s temperature set point,” explains Nolen-Walston. That is, the hypothalamus determines the horse’s “normal” body temperature and acts to maintain a consistent internal temperature despite fluctuations in the external world. When the body’s internal temperature deviates too far from normal, the hypothalamus triggers a cascade of involuntary actions to “adjust the thermostat.”

If the horse starts getting too cold, smooth muscles in the skin contract to raise the hairs on his body, trapping an insulating layer of warm air against the skin; muscle contraction also produces vasoconstriction, a narrowing of the blood vessels in the skin, to cut down on the heat escaping into the air. If he remains cold too long, he will begin shivering to generate heat. The hypothalamus might also stimulate the release of adrenaline and other hormones that increase metabolism, effectively causing tissues and organs throughout the horse’s body to “burn hotter,” and prompts behavior changes: The horse seeks shelter. Conversely, if the horse gets too hot, the hypothalamus initiates activities to reduce body temperature. The muscles supporting each hair will relax so his coat lies flat, and the blood vessels widen to facilitate radiation of heat away from the skin. If that’s not enough to cool him down, he will begin sweating.

The process that produces a fever begins when the immune system encounters a pathogen, such as a bacterium or virus. Among the first responders are lymphocytes, which initiate a cascade of biological events. To help neutralize the effects of the pathogens and eliminate them from the body, these cells release large number of cytokines, blood-borne protein messengers that affect the behaviors of other cells. Many of these cytokines have a pro-inflammatory effect---they stimulate all of the familiar signs of inflammation: localized heat, pain, swelling and redness. One type of cytokine, called a pyrogen, circulates in the blood and is detected by the hypothalamus, which responds by raising the body’s “set point” to a higher temperature. “Fever is one aspect of inflammation,” says Wilson. “We think of inflammation as redness, heat, pain and swelling---and fever is often a part of that.”

The raising of the body’s temperature set point is what distinguishes a true fever from other forms of overheating. “If there is something wrong in the body, like an infection, the body produces chemicals that change that temperature set point and make it higher for a while, and this is a fever,” says Nolen-Walston. “In other situations the body simply becomes hotter but the brain set point hasn’t changed.”

When the set point is raised, the hypothalamus stimulates the body to heat itself just as it would if it were in a cold environment. Vasoconstriction traps heat in the interior of the body, while the metabolic rate goes up. Eventually, the horse might start to shiver
to generate more internal heat, even on a warm day.

If a fever starts getting too high, the hypothalamus may abruptly switch to cooling mode: “The second stage of fever involves sweating and panting, and dilation of blood vessels at the skin surface to route more blood to the skin for cooling---making the skin feel hot,” says Wilson. “The horse is breathing hard to try to get rid of the extra heat via the respiratory system.”

How a rise in body temperature helps fight off infection isn’t entirely understood. “There is a lot of debate in human and veterinary medicine regarding the benefits of fever,” Wilson says. “It may improve healing by speeding up chemical reactions in the body and improving inflammatory reactions to foreign invaders.” The extra heat may also inhibit the activities of temperature-sensitive viruses and bacteria. “We think the higher temperature increases the horse’s metabolism and thus the ability to fight off infections,” says Nolen-Walston.

What we do know is that, as the infection wanes, the immune response eases, the levels of pyrogens in the bloodstream drop, and the body’s temperature set point will return to normal.

A Mild Fever

You might suspect something is wrong if your horse acts a bit dull and goes off his feed. But the only way to be certain that he has a fever is to take his temperature (see “How to Take a Horse’s Temperature,” page 29). You also need to know your horse’s normal temperature to interpret the results. A thermometer reading of 100 might be normal for most horses, but if your horse’s temperature is usually closer to 98, then 100 might be a mild fever.

A slightly elevated temperature---just two or three degrees higher than normal---that lasts only a day or two does no harm and is not usually a cause for concern. Your horse may simply be fighting off some mild infection you might never have noticed. If he was vaccinated recently, a slight fever might be just a side effect of building his immunity. If all you notice is a fever of less than two or three degrees and a slight dullness, you might just let your horse rest and check his temperature periodically for the next day or two. Because fever is an active part of the immune system’s function, you might actually prolong the illness if you give the horse medication to bring it down. Consider calling your veterinarian, however, if the fever persists for several days or if the horse begins showing other signs of illness.

“Most of the time we get called out for some other reason, rather than a fever. There are usually other important signs of disease that are noticed first, such as the horse has stopped eating or is breathing hard, rather than the fact that the horse has an elevated temperature,” says Wilson. “Some people, however, do take their horse’s temperature every day and may notice the fever before the horse is showing other signs of illness. I recommend doing this, because the horse’s temperature is good information to tell the veterinarian before he/she comes out to look at the horse.”

When faced with a horse with a mild fever but few if any other signs of illness, a veterinarian will first try to identify the cause. “A good history of the horse through the past day or days can be helpful. Was the horse coughing, or was there a change of diet or any evidence of diarrhea? Was there exposure to other horses that may have been sick? Did the horse have some kind of injury or serious wounds? All of these things might direct us to a diagnosis and the cause of the fever,” says Wilson.

“Then we usually try to determine which body system might have an infection, causing the fever. We listen to the lungs, check for diarrhea, look at the gums, etc.,” she adds. “Probably the biggest thing that helps us in diagnosis, however, is to run bloodwork on the horse. A complete blood count will help us know the degree of inflammation. Changes in white blood cell counts usually indicate an active infection, depending on which types of cells are elevated in number. This may help us know whether the infection is viral or bacterial.”

If the general examination yields some clues, the veterinarian can pursue more specific tests. “The ultimate way to diagnose an infectious disease is to test for that specific disease, usually by running some kind of bloodwork,” Wilson says. “The problem, however, is that there is no general screening test; you have to make an educated guess as to what it might be and then test for that particular disease.”

Often, however, the cause of a mild fever is elusive. “If we can identify a specific cause such as a virus or bacteria, we will try to target that disease process with the appropriate treatment,” says Wilson. “Unfortunately, even if we test for all the common things it might be, sometimes the tests all come back negative. The horse still has a fever, and we are scratching our heads as to why.”

If the horse seems generally well apart from an unexplained mild fever, the veterinarian might opt not to treat it. “Fever in itself is usually not a problem in horses,” says Nolen-Walston. “We almost never see brain damage from fever in horses. The important thing for horse owners to remember is that there is usually nothing particularly dangerous about the fever itself.”

The decision to treat the fever will depend on the horse’s general attitude. “Most of the time we treat a fever because the horse feels miserable and won’t eat or drink. Every horse is different regarding whether and when he might not feel good,” says Nolen-Walston. “If your horse’s temperature is 102 or 103 and he is happy---eating and drinking---there is no need to specifically treat the fever.”

A High Fever

A high fever---elevated by three or more degrees---is a more serious warning sign. In addition to dullness, you might see chills/shivering, sweating, increased respiration and pulse rate, fluctuations in skin temperature or reddening of the gums. An acute fever tends to spike high but come down quickly. A persistent high fever could indicate a serious illness. Either way, it’s a good idea to call your veterinarian.

“A few infections tend to cause very high fevers,” says Wilson. “Whenever I see a horse with a fever of 105 or higher, my first thoughts for possible causes would include strangles0, anaplasmosis0 and Potomac0 horse fever and some of the viruses, such as equine0 influenza. Often a viral infection will induce a higher fever than a bacterial infection, but this alone is not a good way to try to diagnose what is wrong with your horse.”

Another cause of high fevers is endotoxemia---a systemic inflammatory condition that develops when toxins released by certain bacteria as they die get into the bloodstream. “Horses are uniquely sensitive to endotoxins that are produced by a molecule that is part of the cell wall of gram-negative bacteria,” says Wilson. “There are a lot of these bacteria inside the horse’s intestine as normal inhabitants. They live and die there and go through their life cycle in the colon. When a horse has colitis0, some of the endotoxin from the bacteria’s dead cell walls may leak through the colon lining into the bloodstream. This causes a very dramatic cytokine response---and fever.” Endotoxemia can also occur if tissues of the lungs or uterus are inflamed.

Usually, a horse with a high fever will show other obvious signs of illness that point toward a specific cause. “If there are swollen lymph0 nodes under the jaw or thick nasal discharge, this would make us suspect strangles. If the horse has a cough or abnormal lung sounds, we will suspect a virus or pneumonia. With Potomac horse fever, we would probably see diarrhea or signs of laminitis,” says Nolen-Walston. “If the horse has a colic in which the intestine is twisted, we may see endotoxemia and high fever along with severe colic pain. Horses with anaplasmosis may have a high fever with no other signs except maybe mild swelling
of the legs.”

With appropriate testing to confirm the diagnosis, a veterinarian will begin treatment for the disease as a whole, which will also ultimately address the fever as well.

Too High To Tolerate

Extremely high fevers---above 106 degrees---or any fever that goes on for too long can eventually take a physiological toll on a horse. The body uses calories and water to maintain the higher temperature, which over time can lead to weight loss and dehydration. Prolonged high temperatures may change the chemical structures of heat-sensitive enzymes, which can affect metabolic functions throughout the horse’s body. What’s more, too high a fever may make a horse’s immune response less effective.

That said, in practice, a veterinarian’s main concern is likely to be the effects a very high fever has on a horse’s willingness to eat and drink. “Rarely do temperatures get high enough for long enough time to actually damage tissues that are crucial for the animal to function,” says Wilson. “The biggest reason we end up treating fever most of the time is because a fever makes the horse feel bad. If the horse feels miserable he won’t eat or drink, and this can lead to secondary problems.”

For that reason, your veterinarian is likely to administer medications specifically to attempt to bring down a very high fever in addition to other treatments for the underlying disease. “The first thing we’d use to treat a fever is a nonsteroidal0 anti-inflammatory drug [NSAID] like flunixin meglumine [Banamine] or phenylbutazone [bute],” says Nolen-Walston. “These will often bring down a fever.”

These drugs do have to be administered with care, as directed, however. “The important thing for horse owners to know is that these drugs do not work any better if given at higher doses than recommended by the veterinarian, and they will actually be harmful,” says Nolen-Walston. She has treated horses who were hospitalized after their owners administered additional medication when the prescribed doses failed to curb the fever. “The owners told me they didn’t have any choice because the fever didn’t come down.
But if the fever doesn’t come down with the proper dose, giving more will be toxic,” she says. “I have seen horses die from too much Banamine
or bute.”

If your horse has been prescribed one of these medications, and his fever does not come down as expected, says Nolen-Walston, “consult your veterinarian to see what the highest safe level is. The important thing to remember is that these drugs are much more toxic when the horse is not eating or drinking. If the horse is feeling miserable and you are giving NSAIDs and he is not getting any better, don’t give these drugs for more than a day without having your veterinarian take a look and give you some more advice.”

If medications alone are not enough to reduce your horse’s fever, your veterinarian might suggest alternate methods of cooling him down. “Often we try to cool the body in some other way, by using fans or cold hosing, to help increase evaporation over the entire body,” says Nolen-Walston. “If the horse is really overheated, we can give cool intravenous fluids. You don’t have to cool the fluid very much, because even at room temperature it will be lower than body temperature.”

Cold hosing and fans can also be used to cool a horse at home, but remember that fever is only one symptom of a bigger issue that needs to be addressed. “If you are trying to bring down a horse’s temperature and cold water hosing isn’t doing the trick, call your veterinarian,” says Nolen-Walston. “Unless he/she tells you to do something else, most of the time you can wait for the veterinarian to arrive. It would be unusual that the horse would be in critical shape just from fever, but you could work at reducing the high temperature.”

As your horse recovers, it’s a good idea to keep tabs on his temperature at least once daily for another week or two. “There are certain specific diseases that cause fever for a day or so and then the temperature will drop back to normal,” says Nolen-Walston. “Then in three or four days the horse will have another fever. You can’t assume that just because the fever went down for one reading that you’re out of the woods.”

A mild fever may leave your horse feeling sluggish for a time, so it’s best to let him have some rest while he recovers. Most of the time though, a fever is just a sign that his immune system is keeping things under control, and your horse will be back to his old self in no time.

This article first appeared in EQUUS issue #448, January 2015.

Thursday, February 21, 2019

The Challenge of Cellulitis

Prompt, aggressive treatment is needed to stop this sudden, painful skin infection—and to prevent it from becoming a chronic condition.

Cellulitis On A Horse's Leg
Few situations shout “Emergency!” louder than a horse refusingto bear weight on a grossly swollen leg. Suddenly one task supersedes the whole day’s plans: Call your veterinarian. washingleg

“A lameness with significant swelling should be seen by a veterinarian as soon as possible,” says Meg Hammond, DVM, of Woodside Equine Clinic in Ashland, Virginia. You’ll want to keep the horse still while you wait---if it’s an injury, making him walk even a few steps could make it worse.

The greatest fear, of course, is that the lameness is caused by a fracture or another severe orthopedic injury. But occasionally the source of the problem is something less dire yet still a challenge to treat: an infection called cellulitis.

“Cellulitis is somewhat common in the horse world, but it can be frightening for an owner,” says Hammond. “The leg can be normal one day and double or triple in size overnight. If the leg is infected, the swelling will not resolve with nursing care alone.”

Immediate, aggressive therapy with intravenous antibiotics and anti-inflammatory medications is needed to bring the swelling down and control the infection as quickly as possible. Most horses readily recover from a bout of cellulitis and return to their previous level of activity. But life-threatening complications are possible, especially if treatment is delayed. And for some horses, the initial bout of acute cellulitis will be just the first of many chronic flare-ups.

Making that emergency call to your veterinarian is the most important first step if your horse develops cellulitis. Here’s what you need to know about what comes next.

HOW THE INFECTION DEVELOPS


Normal skin consists of three layers: the epidermis, the tough, external shield that forms one of the body’s first lines of defense; the underlying dermis, the flexible, sensitive layer that contains glands, hair follicles, capillaries, nerves and other structures; and the subcutis, which is made up largely of connective and fatty tissues.

Cellulitis develops when bacteria penetrate below the epidermis and multiply in the subcutis. The infection is diffuse, meaning that it spreads over a wide area without a specific point of origin. How the bacteria penetrate the dermis and subcutis is often unknown---a situation that is called primary cellulitis.

“In nearly half the cases we never really know what started the infection,” says Margaret Mudge, VMD, DACVS, DACVECC, of Ohio State University. “There is no known trauma or obvious wound. We don’t know if the bacteria were already in the horse’s body or if they were introduced through the skin. They may get dragged in through tiny punctures that we can’t see. They may get through the skin if there is enough damage to the underlying tissues that the barrier is compromised.”

On the other hand, secondary cellulitis develops when bacteria gain entry through a wound, surgical incision or another known route. Breaks in the surface caused by dermatitis, the technical name for inflammation of the outer layers of skin, can also allow bacteria in. “When the integrity of the skin is compromised, bacteria can gain entrance and replicate in the underlying tissue,” says Hammond. “It is impressive what can happen when that barrier is damaged.”

A variety of bacterial species have been implicated in cellulitis, but the infection is usually caused by Staphylococcus aureus and Streptococcus species. “These are common bacteria that are often found on skin,” Mudge says. Other bacterial species that may be involved include Enterococcus and Actinobacillus species. “Occasionally, cellulitis can be due to infection with Corynebacterium or Clostridium or a gram-negative bacterium such as Escherichia coli,” says Callie Fogle, DVM, of North Carolina State University.

Secondary cellulitis can develop anywhere on the body where a wound occurs. Primary cellulitis usually develops on a leg, and most often the hind legs. “The term ‘cellulitis’ is very general, referring to infection under the skin and sometimes involving the skin,” says Mudge. “But when we talk about cellulitis in horses we tend to think of the hind limb.” Even when it initially seems mild, cellulitis is not an ailment to take lightly. The swelling can progress quickly, even within a few hours, to the point where fluid leaks from cracks in the overstretched skin.

Plus, if the infection is not controlled quickly, a number of serious complications can develop. For example, the bacteria may spread from the skin into the deeper tissues and structures of the leg. “A particularly aggressive or resistant bacteria may cause tissue necrosis0 or a more deep-seated infection, which in rare cases can affect the bone, tendon or synovial structures such as a joint or tendon sheath,” says Hammond.

Laminitis is also a possibility. “It’s usually a support-limb laminitis but it can also be laminitis in the affected leg,” says Fogle.

Systemic infections, such as sepsis0, can also occur. “Horses can have further problems if the bacterial infection does not stay confined to that limb and goes throughout the body,” Fogle says. “The horse can become very sick from systemic infection. These are all risks with severe cellulitis, but are more likely in cases with a delay in the start of therapy.”

IDENTIFYING THE PROBLEM


Cellulitis is most common in a hind limb, but it can also occur in a front leg or on other parts of the body. “The classic form of cellulitis is unilateral, affecting just one limb, but it can affect multiple limbs,” says Fogle. Here are the common signs:

Swelling that is dramatic and appears suddenly. “The leg is usually diffusely enlarged, sometimes all the way from the foot up to the stifle or beyond, and the typical case is generally swollen from at least the foot to the hock,” says Mudge. The leg may be two or three times larger than normal, and the swelling will be firm to the touch.

Severe pain. “These horses are generally very lame, but often the pain occurs when advancing the limb rather than from standing on that leg; it’s difficult or painful to move the limb,” Fogle says. “Generally, the horse will bear reasonable weight on the affected limb when not being asked to move, compared to a non-weight-bearing lameness that is commonly seen with a fracture or a joint infection.”

Heat. “The leg is usually very warm and painful to the horse if touched,” says Mudge.

Fever. The horse’s temperature is likely to be elevated, and his heart rate may be increased. His overall attitude may be dull, and his appetite low.

Wetness on the surface of the skin may be noticeable, especially if the swelling is dramatic. “Depending on how severely swollen it is, the leg may be oozing serum, weeping through the skin,” says Mudge. These breaks in the skin may have been caused by the initial trauma, or the skin may be so overstretched that the yellowish serum seeps out.

TREATMENT PLANS


Once cellulitis has been diagnosed, treatment will begin immediately. “The longer the leg stays swollen, the greater the risk for complications,” says Fogle. “It is crucial to treat acute cellulitis right away and be as aggressive as possible, within the owner’s financial ability.”

The primary treatment is an aggressive course of intravenous antibiotics as well as nonsteroidal anti-inflammatory medications such as phenylbutazone to address pain and inflammation. Initially a broad-spectrum antibiotic may be administered, but once the results of any cultures are in, the veterinarian may switch to another antibacterial agent that more specifically targets the source of the infection.

Cold hosing is an easy and fairly effective way to address the pain and swelling of cellulitis. “Cold water therapy is helpful, whether it’s one of the fancy boots that recirculates cold water, or just cold water from a hose,” says Fogle.

Bandaging may also help to control the swelling, if the horse will tolerate it. “Some horses will be so painful that they won’t tolerate having a tight bandage on the leg,” says Mudge. “They may protest the bandaging but tolerate cold hosing. Cold therapy can be a good way to reduce the heat and potentially some of the swelling.”

Finally, steroids might be an option, but they must be used judiciously. “Steroids are commonly used by veterinarians to address minor distal limb swellings, but we can run into trouble with steroids to treat severe cellulitis because they can effectively mask whether or not we’re successfully resolving the bacterial infection in the limb,” says Fogle. “Short-term steroid use with a bout of acute cellulitis is OK, but you wouldn’t want to use it very long.”

As a horse’s condition improves, walking can help improve his circulation and pull fluid out of the leg. “Exercise is not feasible when a horse is in an acute bout of cellulitis,” says Fogle, “but getting him moving once the severe symptoms are starting to wane is important.”

Milder cases of cellulitis may be treated on the farm, especially if the owner is comfortable with administering the pain medications and antibiotics as well as cold hosing and bandaging. However, says Mudge, “there are horses who are so painful that they need to be managed in a hospital with more continuous or higher powered pain medications.”

Serious complications might also warrant hospitalization. “Some horses become systemically ill from this infection,” Mudge says. “If the horse has a fever and has gone off feed or is showing signs of laminitis, that horse might be referred to a hospital for more intensive treatment.”

THE ROAD TO RECOVERY


Most horses who develop cellulitis recover completely, especially if treatment begins promptly and they start to respond within the first 24 to 48 hours. “The majority of horses will respond to aggressive medical treatment,” says Fogle. “Often those horses won’t develop any of the chronic effects or complications of cellulitis.”

Horses with secondary, rather than primary, cellulitis tend to recover more quickly. “The prognosis is generally better in the cases where there’s a known injury such as a laceration or some kind of trauma, or cellulitis related to a surgical procedure,” Mudge says. “Those horses seem to do a little better than the horses that have recurrent bouts of primary cellulitis that are not due to a known skin injury. The primary cellulitis cases are often more challenging to resolve in the long term.”

But cellulitis can have long-term effects. Extreme inflammation can stretch and scar tissues enough to compromise the lymph system’s ability to draw out excess interstitial fluids (the fluid that fills the spaces between body cells) and return them to the bloodstream. “Damage to the lymph vessels will interfere with normal drainage of fluid from the limb,” Hammond explains. “With this decreased efficiency of the lymph system, these subcutaneous tissues may always hold a little extra fluid, making the leg appear slightly swollen even after it has healed. This is most likely to happen in the more severe cases or the ones that are not treated early.”

The change in the leg’s appearance may be permanent. “I warn owners that even when horses respond well, they may end up with a leg that is slightly bigger than the other one,” says Mudge. “Even if everything goes well and the horse makes it through and recovers without residual lameness, there may be some limb enlargement. It is yet to be determined whether prolonged bandaging or using things like compression cold therapy make a difference in the final outcome, though these strategies make a lot of sense in continued treatment for these horses. At this point in time, however, we don’t have strong evidence to say whether those will ultimately improve the cosmetic outcome.”

FROM ACUTE TO CHRONIC


Unfortunately, even a single episode of cellulitis can leave a horse susceptible to the chronic form of the condition---repeated episodes of severe, painful limb swelling. “A horse who has recovered from cellulitis is more likely to have a recurrence in that same limb,” says Hammond.

One reason may be that the infection and extreme swelling did some permanent damage to the skin, leaving it more porous. “Inflammation can cause damage to the skin and decrease its effectiveness as a protective barrier,” says Hammond.

Another possibility is that the permanent damage to the lymphatic and blood circulatory systems diminishes the ability to mount a new immune response. “We think that these repeat episodes may be due to scarring and permanent impairment of the venous and lymphatic systems in that limb,” says Fogle. “Once those systems are impaired, the horse is less able to fight infections in that limb. That limb is more vulnerable, and even a small amount of bacteria is capable of starting an infection.”

Chronic flare-ups of cellulitis behave a little differently than the initial acute disease. “It may come on more insidiously than suddenly, compared to acute cases,” Mudge says. And the physiological source of the swelling may differ as well: “The swelling with chronic cellulitis is commonly thought to be poor circulation and inflammation, with less contribution from bacterial infection of the deeper tissues,” says Fogle.

Horses prone to chronic cellulitis will need to be closely monitored; even the tiniest of wounds on the leg may spark a new bout of pain and swelling. “One of the things that owners can do to try to prevent recurrence in that limb is to be vigilant about feeling the skin in the fetlock and pastern area, checking daily for any scabs, scratches or abrasions,” says Fogle. “It’s wise to clip and clean any breaks in the skin on that limb with a gentle soap and allow it to dry.”

Regular turnout and exercise are also recommended to encourage circulation in the affected leg---with some cautions. For one, turnout in wet grass is not ideal. “When the skin is wet it becomes softer and more vulnerable to being nicked or scraped, and it’s easier for bacteria to gain access,” says Fogle. “Keeping the at-risk horse in until the grass is dry is best.”

Bandaging can help to limit swelling when the horse is in a stall. “Several different types of bandages can be useful,” says Fogle. “A quilt and polo wrap or special bandages called short stretch bandages can be used to try to minimize the amount of edema that develops when a horse is stalled. Once these horses are turned out, they don’t need the bandaging.”

Shipping boots are a good idea while in the trailer, and polo wraps can protect the horse’s skin during exercise and competition. “Owners with horses that have chronic cellulitis are usually pretty careful about protecting the limb while they are riding or when trailering,” says Fogle. But the precautions are worth it: “The exercise is really helpful, to improve the blood flow to the limb and improve the circulatory system and lymphatic drainage,” she says, “so it’s often best to continue using the horse, as long as he is sound. As long as you protect the skin, exercise is great.”

Proactive antibiotic treatment is sometimes helpful, too. “I have several owners who have horses affected with chronic cellulitis,” says Fogle. “When they identify a break in the skin, they contact their veterinarian and get the horse on a round of antibiotics to try to prevent another exacerbation of cellulitis. They have developed a very successful proactive approach to try to manage the limb and prevent further bouts of cellulitis.”

PREVENTATIVE MEASURES

Why some horses develop cellulitis while others don’t isn’t well understood, so it’s impossible to identify definitive ways to prevent the infection. “Sometimes in a horse that had some dermatitis or we find a small scratch, we suspect that was what set it off,” says Margaret Mudge, VMD, of Ohio State University, “but there are many horses that have mild dermatitis or lots of cuts and scrapes that never develop cellulitis.”

Nevertheless, taking some basic precautions to protect the skin on your horse’s legs will not only keep him healthier and more comfortable, but might just help you ward off this terribly painful infection:

Clean and disinfect even the smallest of wounds. “As soon as you notice anything abnormal, it should be treated promptly and appropriately,” says Meg Hammond, DVM, of Woodside Equine Clinic in Ashland, Virginia. Call your veterinarian for help with deeper, more serious wounds.

Maximize turnout and/or get the horse regular exercise. Moving around stimulates healthy circulation in any horse, but it’s especially critical for those prone to cellulitis.

Keep the skin dry. Muddy, sloppy turnouts are unavoidable for farms in wet climates at certain times of the year. Do, however, make sure horses have access to dry shelters where they can find some respite. Laying gravel in low, muddy areas can also help keep their legs cleaner. Bringing turned-out horses inside once a day will give you the opportunity to clean and inspect their legs and let them dry out.

Go easy on the shampoo. Over-exuberant soaping up will dry out skin and may lead to cracking.

Groom carefully. Removing long hair on the legs can help keep the skin drier, but be careful not to scratch the horse with the clippers. Also use only soft brushes and rags on the legs.

Sterilize grooming and bathing equipment periodically. Newer washing machines have a sterilization option that can heat rags and towels to a temperature high enough to kill most bacteria and other pathogens. Brushes and other tools can be sterilized by scrubbing them with soap and water before soaking them in a bleach solution and laying them in direct sunlight to dry. Avoid sharing tools among horses, especially if one is prone to chronic cellulitis.

Managing a horse prone to chronic cellulitis requires diligence. But with attentive care, there’s no reason he can’t live a long, healthy and productive life.

Monday, January 7, 2019

The Persistent Risk of Rabies

Reservoirs of the rabies virus continue to exist in the wild, posing a threat to both wildlife and domesticated animals.

LAURIE BONNER OCT 10, 2017

Today, the threat of rabies to American horses may seem remote. Vaccination against the disease is extremely effective and affordable. And rabies is rare in the United States: Only 25 cases were reported among horses and mules in 2014, according to the Centers for Disease Control and Prevention. You need not lie awake at night worrying about rabies.

But you don’t want to become complacent, either. Usually transmitted through the bite of an infected animal, rabies is invariably fatal---the virus ravages a horse’s nervous system and there is no cure. In fact, rabies has the highest mortality rate of any infectious disease---functionally 100 percent since euthanasia is the only option once signs of illness appear. And reservoirs of rabies virus continue to exist in the wild, causing periodic outbreaks of the disease that pose a risk to both wild and domesticated animals.

All of which means that even as you vaccinate your horse against rabies, it’s wise to remember the threat the disease poses and remain vigilant.

How infection happens

The rabies virus is spread through the saliva of infected animals. In the United States, the main reservoirs for the disease in the wild are raccoons, skunks, foxes and bats. Rabies has been reported in every state except for Hawaii. Wild animals commonly pass the virus to others of their own kind, but susceptibility to the infection varies among species---for example, to become infected an opossum needs a dose of rabies virus 50,000 times higher than the amount it takes to infect a fox.

Horses typically become infected when a rabid animal wanders into their pasture or enclosure. Rabid animals don’t necessarily attack horses, but a curious horse may sniff the visitor, startling it and leading to a bite.

Equine rabies infection is considered “spillover” of the virus, meaning horses can contract rabies but only rarely pass it on. Routine handling or exposure to a horse’s blood, urine or feces generally does not pose a risk. However, rabies can be transmitted to a person or another animal if an infected horse’s saliva comes in contact with the eyes, nose or mouth or a skin wound or abrasion. In some cases, a rabid horse at first seems colicky, exposing people as they care for him. Later, when the true nature of the problem is determined, the owner, veterinarians and others who had contact with the horse may need to undergo preventive measures.

The damage done

Once the rabies virus enters a horse’s body, it invades the nearest peripheral nerve cell. It then replicates, passing from cell to cell, working its way to the brain. In most cases, a horse won’t show any sign of disease during the incubation period, which can last for weeks or months depending on the dose of the virus and the location of the bite. For example, a horse bitten on the muzzle may show signs of rabies within a day or two, while one bitten on the leg may not become ill for weeks because the virus must travel farther to reach the brain.

There are two forms of rabies in horses. In the “furious” form, generally seen after a bite to the head, the horse becomes aggressive and agitated before paralysis of the face and tongue sets in. The inability of these horses to drink, and their frustration with that, often gives the impression that they are afraid of water. In fact, rabies was historically and mistakenly referred to as “hydrophobia.” But a rabid horse is not afraid of water; he simply cannot drink it. A horse with the furious form of rabies can be extremely dangerous---unpredictable, aggressive and violent.

In the “dumb” form of rabies, typically seen after a bite to a limb, the horse becomes gradually more depressed and weak until he is unable to rise. With this form, the characteristic paralysis of muscles on the face and head takes longer to appear than in the furious form; when it does, it is often signaled by drooling as the virus enters the salivary glands.

Regardless of the form, the earliest stages of rabies can be confused with other diseases, particularly those with a neurological component, such as equine protozoal myeloencephalitis (EPM) or West Nile encephalitis. Misdiagnosis is more likely to occur if the bite wound goes undetected. Within a few days, however, the rapidly spreading paralysis makes it clear something more sinister is at work.

Safeguards against infection

Obviously, the best way to protect your horse from rabies is through annual vaccinations. The American Association of Equine Practitioners classifies rabies as a core vaccine, which means it is recommended for all horses regardless of life stage, lifestyle or location. Currently, three licensed rabies vaccines are available for horses; all are killed-virus products administered annually to mature horses.

Rabies is a reportable disease, which means that a veterinarian is required by law to notify public health officials about potential cases, and management of those cases must conform to state and local health regulations.

If a vaccinated horse may have been exposed to rabies---perhaps a bite wound is found on his leg, for example, or a sick raccoon is discovered in his field---a veterinarian will likely recommend the administration of a “booster” vaccination to ensure that his immune system can fight off the pathogen. (Laboratory tests to check titers of rabies antibodies in a horse’s blood are not a reliable indicator of protection, and there is no risk of overdose with another vaccination.) After the booster is administered, the horse will also be observed for at least 45 days for any signs of rabies.

If an unvaccinated horse is bitten by a rabid animal or otherwise exposed to the disease, the course of action will depend on several factors. In some cases, immediate euthanasia may be recommended. An option in other situations may be immediate vaccination followed by strict isolation and observation for signs of disease for a minimum of six months.

Finally, research by Texas state public health officials has shown that the rabies postexposure prophylaxis protocol (PEP) for domestic animals mandated by the state can be effective in preventing the disease. The Texas PEP calls for immediate vaccination against rabies, a strict isolation period of 90 days, and the administration of booster vaccinations during the third and eighth weeks of isolation. However, because of the public health implications, states and localities have regulations specifying how cases of rabies exposure must be handled; a PEP protocol may not be allowed under those regulations.

SIDEBAR: Rabies: In Brief

Definition: viral disease of the central nervous system

Signs: infection produces no signs until the virus reaches the spinal cord and brain. Once that happens, the horse may show acute (also referred to as “furious”) signs such as aggression, agitation, hyperactivity and paralysis of the tongue and face. He might also show paralytic (or “dumb”) signs, such as depression, weakness, ataxia, recumbency, paralysis and excessive salivation. If not euthanized, the horse will usually die within days.

Causes: The rabies virus is excreted in saliva of infected animals and usually transmitted through bites.

Diagnosis: No definitive laboratory test can identify rabies in a live horse. Diagnosis on a living horse is done through a history and observation of signs. Postmortem examination of the brain can confirm the diagnosis.

Treatment: Nothing can be done once clinical signs appear, which can take days, weeks or months. Immediately after known exposure, a previously vaccinated horse will be given a booster shot and monitored for a minimum of 45 days. In some jurisdictions, an unvaccinated animal may undergo a rabies postexposure prophylaxis protocol (PEP), which entails immediate vaccination, followed by booster vaccinations, and a strict isolation period lasting a minimum of 90 days.

SIDEBAR: Defending the perimeter

Keeping all wildlife away from your horse may seem like a logical defense against rabies. But as a practical matter, that’s just not possible. A better approach is to make your property as uninviting as possible to such visitors. Here are a few suggestions:

Store grain securely and neatly. Spilled or otherwise accessible feed is the wildlife equivalent of an “open for business” sign on your barn. Apply the same standards to your hayloft, keeping stacks tidy and doing a thorough cleaning at least twice a year.

Tear down abandoned buildings. A dilapidated shed you never venture into is a haven for wildlife that could harbor rabies. If you have a shed that’s unused but still in good repair, find a use for it that has you entering several times a week in a loud and obvious fashion. Regular disturbances will likely cause animals to relocate.

Consider adopting a dog. If you don’t already have a regular canine patrol of your property, look into that option. Of course, you never want a dog to encounter a rabid animal, but a vigilant presence may discourage animals from moving into the territory in the first place.

Monday, December 24, 2018

Post-Colic Care for Horses


Knowing how to recognize and manage equine colic is a critical skill for owners, but colic aftercare is just as important to the horse's well-being. If a horse in your care does develop a colic, ask your veterinarian for a detailed post-colic care regime to follow during his recovery. More than likely, it will include the following the suggestions:


Here are 5 things you can do to get your horse back on his feet after a bout of colic.
  1. Watch the droppings. Even after the horse looks comfortable, keep a close eye on the state of his manure. Any change from normal consistency, color or content should be noted; extreme changes, or those that last more than a day after the colic, warrant a call to your veterinarian. Although the horse may not show colic signs, the abnormal manure indicates that his digestive system is still out of sorts.
  2. Forget the grain. Withhold all grain for at least a day, or until his stools look normal. Then return him to his regular feed, starting with just a fraction of his normal grain ration. Gradually increase his grain back toward normal, while observing him closely for trouble signs.
  3. Provide plenty of forage. You can allow a mildly colicky horse to graze as soon as he feels up to it. Grass is easy to digest and palatable. You may also allow him unlimited access to hay if his droppings remain normal.
  4. Turn him out. The movement and selective grazing of continual turnout get a horse's gut moving faster than stall rest. Check on the field-kept horse often to be sure you don't miss signs of returning pain.
  5. Maintain a continuous supply of clean water. Have palatable water available to the recuperating horse at all times. Full hydration is necessary for normal gut function

Monday, November 26, 2018

Subtle Signs of Lameness in Horses

Sometimes lameness in horses isn't easy to see. Here are a few of the less-obvious indications of unsoundness.

EQUUS 12, 2011



A full lameness exam can help pinpoint subtle signs of unsoundness in horses. A horse who is head-bobbing unsound is easy to spot, but more subtle signs of equine lameness can elude detection. Failing to notice when a horse is only slightly "off" can lead to a worsening of an injury or delay in treatment that makes a problem more difficult to resolve. Consult your veterinarian if you see any of the following signs.

  • A hind leg that doesn't reach as far forward as the other with each stride
  • Overall shorter strides or reluctance to "move out" when asked
  • One hoof that consistently cuts deeper into footing than the opposite foot
  • Resistance to picking up a particular lead
  • Refusing or running out at fences
  • A change in movement or demeanor when you post on a particular diagonal
  • More or less flexion in the joint in one limb
  • A "pecking" movement of the front legs, as if the horse is trying to tiptoe
  • Asymmetrical hips or shoulders
  • A significant change in gait when moving from soft to firm footing and back again
  • Resistance to traveling from on type of footing to another

Friday, September 28, 2018

Applied genetics

Dozens of genetic tests are now available that can offer insights into equine health, coat color and even performance potential. Here’s what they can and can’t tell you.

ABIGAIL JEFFERIES NOV 17, 2017

Turn on the radio or television and you can’t miss them: Advertisements for genetic testing are almost as common as commercials for laundry detergent and auto insurance. Just a decade or two ago, such ads were unheard of. Yet today, genetic testing services---for animals as well as people---are more numerous, more accurate, more affordable and more convenient than ever.

“What most folks don’t know about genetics is really how advanced it has become,” says Christa Lafayette, CEO of Etalon Inc. of Menlo Park, California. “Genetics is the new smartphone. Think back to when you first heard someone say, ‘There’s an app for that,’ and you had no concept as to what, exactly, an ‘app’ was. Now they are completely taken for granted and just common knowledge. That is where genetics is headed.”

The first genetic tests for horses became available in the 1990s, and for many years they were used only occasionally. Dozens of tests are now available. Most are being used in breeding decisions that will shape future generations of horses, but others offer insights into the health, beauty and potential of horses here today. As genetic tests become increasingly affordable and accessible, the role they will play in the horse world will only continue to grow.

Identifying inheritable diseases

Many inherited diseases result from single gene mutations that cause changes in how the body functions. The mutation is considered dominant if a foal needs to inherit only one copy of the defective gene to be affected by the disease. If the mutation is recessive, the foal needs to inherit two copies of the defective gene, one from each parent, to be affected. A horse with only one copy of the recessive gene is a carrier---he may be completely normal but is capable of producing a foal with the disease when mated to another carrier (see “Basics of Inheritance,” page 40). A mutation is considered incomplete dominant if a horse with one copy of the mu- tated gene is more mildly affected and a horse with two copies is more seriously affected.

Most tests for heritable diseases are breed specific, and some organizations require testing for particular genes prior to registering breeding stallions to limit the prevalence of certain conditions in the population.

Since 2015, for instance, the American Quarter Horse Association (AQHA) has required all registered breeding stallions to undergo a five-panel test for the following genetic diseases:

• glycogen branching enzyme deficiency (GBED), a fatal condition caused by the body’s inability to store glycogen, resulting in progressive weakness and organ failure

• hereditary equine regional dermal asthenia (HERDA), a connective-tissue disorder which causes fragile skin that tears easily and is so slow to heal and prone to infections that euthanasia is often the most humane option

• hyperkalemic periodic paralysis (HYPP), which is characterized by episodes of muscle weakness and tremors and, in severe cases, collapse and respiratory or cardiac failure

• malignant hyperthermia (MH), a condition in which extreme stress, exercise or anesthesia triggers muscle rigidity, fever, excessive sweating, shallow breathing and an irregular heart rate

• polysaccharide storage myopathy type 1 (PSSM1), which causes an abnormal accumulation of sugars in the muscles leading to cramping, tremors and characteristic dark urine as the kidneys flush the byproducts of muscle damage. Note: Although testing for PSSM1 is required for Quarter Horse breeding stallions, the disease has been found in more than 20 breeds, including several drafts and warm- bloods with European bloodlines as well as American stock horses.

In addition, a test can determine whether Quarter Horses carry the gene for androgen insensitivity syndrome, which causes males horses to have female physical attributes, but it is not required for registration of breeding animals.

Beginning January 1, 2018, the American Paint Horse Association will require all breeding stallions to undergo the genetic tests in the AQHA five-panel profile, plus one other, overo lethal white syndrome (OLWS), which produces foals who are born almost pure white and have undeveloped nerves in the intestinal tract, making it impossible to process food and pass feces. OLWS appears in Paint Horses as well as mustangs, Spotted Saddle Horses and any other breeds that can show a frame overo coat pattern.

While other registries may not require genetic testing for diseases right now, many other tests for breed-related conditions are available, including:

• congenital stationary night blindness (CSNB), which is limited or no nighttime vision caused by a gene linked to the leopard-spotted coat pattern. Leopard spots are best known as a breed-defining pattern in Appaloosas and Pony of the Americas but can also occur in other breeds such as the Knabstrupper, Noriker and some Spanish mustangs.

• junctional epidermolysis bullosa (JEB), which inhibits the production of proteins that help adhere the skin to the body, leading to blistering, sloughing of skin and fatal infections. JEB was first discovered in Belgians (Belgian-JEB); a form of the condition is also found in Saddlebreds (Saddlebred-JEB), although the genetic cause is different.

• severe combined immunodeficiency disease (SCID), which inhibits the body’s ability to produce white blood cells that play a vital role in immune functions, and lavender foal syndrome (LFS), which causes several neurological signs. Both of these are found in Arabians, along with cerebellar abiotrophy (CA), which causes the death of neurons in the cerebellum that affect balance and coordination, and is occasionally found in other breeds.

• ocular squamous cell carcinoma (SCC), a type of tumor that appears on the edges of the eyes and on the third eye- lid, in Haflingers

• warmblood fragile foal syndrome (WFFS), which causes fragile skin that tears easily and is slow to heal, lax joints that may prevent standing, and lesions within the mouth.

Knowing a horse’s genetic status can help an owner make more informed management decisions. If you know your horse is susceptible to ocular SCC, for example, you can make sure to protect him from sun exposure with a fly mask and take other precautions to try to prevent the condition or at least catch it early. Genetic testing is also becoming a common part of prepurchase exams.

While horse owners may find genetic tests useful, breeders are their primary users. By identifying stallions and mares with one copy of recessive genes associated with certain diseases, breeders can avoid mating carriers to other carriers to avoid producing affected foals.

But that doesn’t mean carriers can’t be bred at all---in many breeds, removing all carriers from the breeding pool would severely limit genetic diversity. “If we were to eliminate all horses that had one copy of one of the five-panel disorders, we would probably eliminate 30 to 40 percent of all American Quarter Horses, thus greatly reducing the gene pool,” says Arne de Kloet, director of Animal Genetics in Tallahassee, Florida.

By breeding carriers of undesirable genes only to noncarriers, breeders can avoid producing foals with recessive diseases while still preserving other desirable traits these horses may have. “Animal Genetics reports all SCID test results to the Arabian Horse Society,” says de Kloet. “Interestingly, the number of carriers we see is almost the same as it was 15 years ago, but the number of homozygous [horses with two copies of the mutation] positives we see is almost zero. This tells me people have been breeding smart. If I have a stallion that has one copy of SCID, I’ll never breed him to a mare that also has a copy of SCID, and we’ll never have a problem. This enables horses with many great qualities to remain in the breeding program.”

Currently, genetic testing is required only for Quarter Horse breeding stallions, but many breeders are opting to test prospective broodmares of the breed as well. “There is both breeder wisdom and market pressure pushing increased testing of mares,” says Cecilia Penedo, PhD, director of the Veterinary Genetics Laboratory of the University of California–Davis.

Even with the new information that genetic tests can provide, breeding decisions still require a balancing act. “Some mutations have been maintained for advantage,” says Kathryn Graves, PhD, director of the Animal Genetic Testing and Research Laboratory of the Gluck Center at the University of Kentucky. “The PSSM1 mutation may have given working draft horses superior abilities to pull or carry heavy loads. The mutation that has given us the beloved Appaloosa color pattern that can also be associated with night blindness, but do we want a world without Appaloosas? We have to be careful not to make our first response a rush to eliminate all mutations. The irony is that genetic testing is giving us new tools to undo the results of our own selective breeding.”

Colors, patterns and parentage

Genetic analysis isn’t all about health, though. Tests are also available that provide insight into your horse’s coat color, patterns and parentage ---traits that may seem obvious at first, but a peek at your horse’s DNA can reveal surprising or otherwise un-knowable information.

Testing can determine whether a horse carries one, two or no copies of the genes required for more than a dozen coat colors and patterns. These include

• base colors, which will be either black, red or bay.

• dilution factors, which are five testable genes that modify the color of the base coat. These are champagne, cream, dun, pearl and silver.

• patterns, which are genes that eliminate pigment and produce white hairs on the body, including dominant white, gray, tobiano, splashed white, overo, sabino, leopard complex and roan.

Tests for coat colors and patterns are relatively inexpensive, and they can be used by owners who simply want to know what color their horses are. Many coat colors can look very similar ---a palomino, for example, can be hard to distinguish from a silver-dappled bay---and if a horse’s parentage isn’t known, the only way to be certain is by a genetic test.

Mostly, however, genetic tests for coat colors and pattern are used by breeders who want to be able to predict what colors their mares and stallions can produce. This capability has both pros and cons, if too strong a focus on coat colors or patterns outweighs other desirable traits.

“There is a definite danger there,” Graves says. “We have seen this happen in some breeds already. For example, if a registry has strict color requirements and horses of any other color are excluded, the breed runs the risk of becoming inbred, which may bring consequences such as infertility or an increase in the prevalence of other undesirable genetic traits.”

These tests are more critical in the case of the frame overo pattern. Breeders need to identify horses who carry this mutation to avoid producing a foal with lethal white syndrome. One of the splashed white genes may also produce lethal white foals, but that connection has not been proven.

Finally, confirming parentage of a horse was one of the original uses of genetic testing and remains one of the most common. A number of breed organizations require that foals have their parentage confirmed before they can be registered. These tests require the submission of hair samples pulled from the foal as well as from both his sire and dam. If the sire is uncertain, then samples can be submitted from all possible sires.

By comparing inheritable traits in the DNA, these tests can confirm a foal’s parentage with efficacy greater than 99 percent; an incorrect sire can also be excluded with 100 percent certainty. “We compare the genetic profile of the sample of mane or tail hair submitted to our database profiles of the sire and dam,” Graves says. “We verify the parents and send those reports to the registries.” However, these tests do not reveal the breed of an individual horse.

Owners seeking to register their horses are the most common users of equine genetic testing. “The DNA test for parentage verification represents the largest number of samples tested,” Penedo says. “Most horse breed registries now require DNA testing for registration, which translates to hundreds of thousands of horses being tested yearly around the world.”

What lies ahead?

Like many other technologies, genetic testing is becoming faster, more affordable and thus more accessible. “The cost of sequencing a horse’s entire genome is coming down,” Graves says. “Today, this can be done for about $8,000 to $10,000. Soon, perhaps within 10 years, it will cost only about $1,000. At that point, the average horse owner will be able to sequence her horse’s entire genome.”

The challenge, says Graves, will be determining how best to use this information. “We still have a lot of work to do before we will know that,” she says. “We need to create maps of each breed of horse. This will enable us to look for desirable performance traits or for genetic anomalies in a horse that has chronic health problems.”

Could genetically engineered “super horses” appear in the future? Possibly, with a new technology called “gene editing,” which Penedo describes as using “molecular scissors” to insert, remove or replace DNA sequences in the laboratory. “I can envisage that it will be tried in horses, but given the costs it is unlikely to become common practice,” she says. One application of this technology that she does foresee, however, “would be to correct the DNA sequence in an early embryo from highly valuable parents that is affected with a genetic defect, as determined from pre-implantation embryo genetic testing. The expectation is that the defective gene could be replaced by a normal gene, and the ‘edited’ embryo could then be implanted.”

In the meantime, the number of specific tests available---both for diseases as well as other aspects of a horse’s health and physiology---will likely continue to grow as researchers learn more about equine genetics. “It is a constantly evolving field,” de Kloet says. “Just as with human genetics, it’s going to change and evolve in the number of tests available and with regard to how the testing is being done. We have software programs and the computer ability to go through and look at a billion nucleotides in only a couple of days.”

To help with further research, Etalon Diagnostics offers several tests to the public, for conditions such as lordosis (“swayback”), that are in the “discovery stage”---that is, although there is some evidence of genetic factors for these conditions, the results of these specific tests have not been fully validated by research studies. Etalon’s goal is to gain feedback from owners to help support the research.

“Our platform is collaborative, meaning that it relies in part on feedback from horse owners,” Lafayette says. “We look for associations between certain genetic mutations and performance or other health traits based on emerging research data. When we see a pattern that suggests a genetic link, we follow up with horse owners and track the input we receive from them. This leads to the discovery or confirmation of connections between genetic mutations and resulting traits faster than would be possible if we were to go the conventional research grant route.”

Lafayette admits, however, that this approach is still a work in progress: “Since this kind of horse- owner-driven research platform has never been attempted before, the learning curve is steep,” she says. “We have to continually adjust our methods, studies, and the way we approach and present the information.”

The demand for genetic testing is already large and is likely to continue to grow in the coming years as the technology develops and new tests become available. Already, says Lafayette, labs like hers are receiving all kinds of requests from people who want more information about their horses: “Big ones, little ones, wild ones and pocket ponies, all colors, all disciplines. People want to know everything from color and health to speed and gait. Folks are excited to talk and learn more about their horses, as are we.”

This article first appeared in the August 2017 issue of EQUUS (Volume #379)

SIDEBAR

Performance and personality testing

While genetic tests for diseases, colors and parentage can provide DNA “proof” of a condition, those looking for genes associated with performance-related traits yield less definitive information. How or whether these genes are expressed can be influenced by training, environment and other factors.

For instance, performance testing, aimed primarily at Thoroughbreds, looks at multiple genes to attempt to predict a horse’s speed, stamina and overall potential for success at the racetrack. One factor these tests analyze is the myostatin gene, which controls the amount of muscle mass developed. Other components of the tests may predict a foal’s height at maturity as well as whether he will do better on dirt versus turf tracks.

Gait testing identifies a mutation on the DMRT3 gene that influences a horse’s ability to perform lateral gaits. The mutation is recessive—horses with two copies of the gene are common in Icelandic Horses, Paso Finos, Tennessee Walking Horses and other gaited breeds. The effects of carrying only one copy of the mutation varies by breed, but those horses generally perform the lateral gaits with less speed and facility.


Having a particular “performance” gene isn’t a guarantee, however. After all, many a racing phenom has had full siblings who washed out at the track, and every so often a horse with a modest pedigree takes the show world by storm. DNA is only part of the equation.

Another test, described by its manufacturer as “curiosity vs. vigilance,” analyzes a mutation that affects dopamine0 receptors in the horse’s brain. Horses with two copies of the recessive gene are defined as more curious—that is, more inclined to take an interest in and approach new objects. Horses with only one or no copies of the gene are more vigilant, or less inclined to explore their surroundings.

“An oversimplified example of this might be that horses who test positive for ‘curiosity’ might outperform those who do not in, say, a trail competition,” says Christa Lafayette, CEO of Etalon Inc. of Menlo Park, California, who adds that the real utility of the test will only be known once owners begin interpreting the results. “It’s going to be interesting to see what owners say about it and whether or not they find a correlation between curiosity/vigilance and certain types of activity.”

This article first appeared in the August 2017 issue of EQUUS (Volume #379)

Answers about ancestry

For as much as equine genetic testing has expanded over the years, one type of test isn’t available yet. “We don’t yet have a test that can tell us what breed or mix of breeds is in an individual horse,” says Kathryn Graves, PhD, of the Gluck Center at the University of Kentucky. “We would be very popular if we could offer this test, because we get requests for it several times each week.”

The challenge is that many of our modern breeds descend from the same foundation stock, and researchers don’t yet have enough genetic profiles of individual horses of different breeds to be able to distinguish them. “While breed identification of purebred horses is more easily done, determination of breed contributions in crossbred horses is a far more complex problem,” says Cecilia Penedo, PhD, of the University of California–Davis. “Perhaps in the near future, this limitation may be overcome by careful selection of DNA markers for breed composition tests to become more informative and accurate.”

This article first appeared in the August 2017 issue of EQUUS (Volume #379)

BY ABIGAIL JEFFERIES

Friday, August 10, 2018

Bring Out Your Horse's Shine


CHRISTINE BARAKAT WITH MELINDA FRECKLETON, DVMOCT 1, 2017

While grooming trends vary among breeds and disciplines, a shiny horse is a head-turner in any arena. Some horses “bloom” more naturally than others, but there are some steps you can take to bring out the shine in any horse’s coat.

1. Don’t bathe him too often. The deepest shines come from the natural oils produced by your horse’s skin. Bathing too often strips this oil, so while your horse may technically be cleaner, his coat may be left looking dull. Skip the soap when you can, removing dirt with brushes and using only plain water to rinse your horse after a sweaty summer ride.

2. Lay on the elbow grease. Regular, vigorous hand grooming spreads oil throughout your horse’s coat, contributing to shine. Even after visible dirt has been removed, spend another 10 minutes brushing your horse to bring out a sheen. A soft brush works best for this final touch, or you can use a clean hand towel and wipe over your horse in the direction of coat growth using a slight bit of pressure.

3. Feed him right. Good basic nutrition is the foundation of a healthy coat, so ensure your horse is getting the correct amounts of quality feed. From that start you can consider adding a supplement intended to bring out the best in his coat. These supplements typically include some combination of biotin and omega-3 fatty acids.

4. Use a finishing spray. A light spritzing with a “shine” spray can put your horse’s glow over the top. There are many formulations of coat polish to choose from with different ingredients, actions and scents. Some of these sprays can make a horse’s coat slick, however, so be careful when applying it to hair you’ll need to braid later or on areas where tack will sit.

This article first appeared in the July 2017 issue of EQUUS (Volume #378)

Thursday, June 21, 2018

The challenge of EPM

Early detection and treatment are the keys to helping a horse recover from this neurological disease.

When your previously sure-footed horse starts to stumble regularly…. Or you notice his lip drooping and he’s dropping feed…. Or his gaits just seem to lack that usual smoothness under saddle….

Signs like these may be subtle, especially at first, but it is not good to overlook them. In fact, any persistent change in the way a horse uses his body---including his resting stance, his gaits, how he carries his tail, the pattern of his sweat, generalized weakness, a drooping ear or tilted head---could be a sign that he is developing a neurological disorder.

And one common neurological disease affecting American horses is equine protozoal myeloencephalitis (EPM). Horses may develop EPM after ingesting feed or water contaminated with Sarcocystis neurona, a one-celled organism called a protozoan, that is spread by opossums and carried by other animals. Less commonly, a different protozoan called Neospora hughesi may also cause EPM.

Most horses who encounter the organisms that cause EPM put up an immune response that fights off the infection. Sometimes, however---in less than 1 percent of exposed horses---the protozoa cross into the central nervous system and damage the brain and spinal cord. Several drug treatments are available that can curb the protozoal infection, but the damaged nerves will still require up to a year or more to heal, and some horses never recover completely. Relapses are common if the protozoal populations are able to rebound after treatment ends. A horse’s chances of a full recovery are better when treatment is started early, before the damage is too severe.

The most common signs of the disease are weakness and incoordination (ataxia), primarily in the hind limbs. Often, the effects are asymmetrical---one hind leg will be affected more than the other. As the disease progresses, the horse may develop muscle atrophy. In rarer cases, if the disease affects the brain, signs may include facial paralysis, seizures, difficulty swallowing, head tilt and behavioral changes.

Diagnostic difficulties

Determining whether a horse has EPM can be difficult. Because most who are exposed to the protozoa never develop the disease, the presence of antibodies alone is not enough for a diagnosis. A horse who is positive for antibodies to one of the protozoa could still have neurological signs due to some other cause.

That said, however, some of the newer testing methods---an indirect immunofluorescence antibody test (IFAT) and enzyme-linked immunosorbent assays (ELISAs)---can be used to determine the titer (the concentration of antibodies) in a blood sample. Although these types of test results are not a definitive diagnosis, many veterinarians consider a higher titer, along with neurological impairment, to be evidence of probable EPM.

The most definitive type of testing looks for antibodies to the protozoa in the cerebrospinal fluid (CSF), which surrounds the brain and spinal cord. Evidence that the organisms have penetrated the central nervous system is an even clearer indication that the horse’s neurological signs are attributable to EPM. Finding high titers of anti-bodies in both the blood and the CSF is the best indication of EPM that is currently available. However, even this evidence is not considered definitive proof that the EPM is the cause of any neurological signs. And because obtaining a sample of CSF is a more technically challenging and more in- vasive procedure, many veterinarians proceed on the assumption of EPM based on the blood tests and observation of signs alone.

Treatment and recovery

Three drugs currently have Food and Drug Administration approval for the treatment of EPM:
  • Ponazuril (trade name Marquis) is an oral paste delivered once daily for 28 days.
  • Diclazuril (trade name Protazil) is an alfalfa-based pellet that can be fed daily as a top dressing on a horse’s grain for 28 days.
  • Sulfadiazine and pyrimethamine (trade name ReBalance) is an oral suspension administered daily for as long as 270 days.
All of these drugs are antiprotozoal and cross the blood-brain barrier to either kill or inhibit the reproduction of the organisms within the central nervous system. The best choice for your horse depends on several factors, including which is easiest to admini-ster effectively.

Your veterinarian will advise you on special handling for the drugs. For example, some evidence suggests that administering DMSO (dimethylsulfoxide) in conjunction with ponazuril may help the drug to reach therapeutic levels faster. Also, especially in more severe cases, a veterinarian may opt to begin the treatment with a “loading dose” of ponazuril, with three to seven times the normal amount, to help the drug reach the central nervous system faster. In a few cases, longer treatment periods are needed.

Preventive measures

Currently, no vaccine is available to protect against EPM. For now, your best bet for preventing EPM lies in limiting your horse’s exposure to the protozoa. And, for the most part, that means taking steps to break the parasite’s life cycle and to prevent opossums from contaminating your horse’s feed and water:
  • Avoid attracting large numbers of scavengers. It is not necessary, or probably even possible, to keep all opossums away from your property. And that’s OK: Opossums eat prodigious numbers of pest species, including mice and ticks, which can also carry diseases. But you do want to keep their numbers to a minimum---and that means closing down the food sources on your farm that would attract opossums and encourage them to stick around.
  • Keep your feed in sealed containers and clean up spills immediately. Use sturdy garbage cans with tight-fitting lids. Pick up uneaten cat and dog food at the end of each day, and clean up fallen seed under bird feeders. If you have fruit trees, pick up fallen fruit. Killing or trapping opossums won’t help---if you’re still providing food sources, more will come.
  • Pick up animal carcasses. Opossums pick up S. neurona by scavenging carcasses of other infected animals---which can be many species, including skunks, raccoons, armadillos and cats. To reduce the risk that local opossums will get infected, remove any dead wildlife you may find on your property.
  • Keep hay and bedding clean. Make an effort to keep any roving opossums away from your horse’s feed and bedding. Store these materials in a secured shed or loft to keep out wild animals, and dispose of any you find that has been contaminated with animal feces. Use feeders to keep hay off of the ground; check them periodically for animal wastes and clean as needed.
  • Seal off the shelters. Clear up brush piles, which can provide shelter for wildlife, and close doors to sheds and other outbuildings, especially at night. Close off access to spaces underneath buildings, too---but first make sure you don’t already have animals in residence. You don’t want to trap them inside.
  • Limit your horse’s stress. Horses who travel frequently and undergo the stresses of training and competing in high-intensity sports are at greater risk of developing EPM, according to a 2000 study from Ohio State University. Your veterinarian can advise you on steps to avoid overtaxing your competition horse and to keep him generally healthy.
For more information, go to “On the Frontlines Against EPM” (EQUUS 451).

The life cycle of sarcocystis neurona

The opossum is the definitive host for Sarcocystis neurona, meaning that the protozoa can mature and reproduce within its body. 1. The opossum excretes the parasite eggs, called oocysts, in its feces. 2. The oocysts release a secondary stage, called sporocysts, which may contaminate feed or water and be consumed by other animals. 3. The horse may ingest sporocysts. Horses are considered aberrant hosts because, so far, no evidence has been found that the protozoa complete their life cycles in horses. 4. In some cases, the protozoa may cross into the horse’s central nervous system and damage the spinal cord and/or brain, causing equine protozoal myeloencephalitis (EPM). 5. Other animals—including raccoons, skunks, cats and armadillos—may ingest the sporocysts and become intermediate hosts. 6. Once inside the intestine of an intermediate host, the sporocysts hatch and go through other life stages. Even-tually, they invade the muscle tissue and form sarcocysts, which contain parasite spores. 7. When the intermediate host dies, its carcass may be scavenged by an opossum, which ingests the sarcocysts. The parasites mature in the opossum’s intestine, and the cycle begins again. Note: The life cycle of Neospora hughesi is less understood, but it appears that horses do not have to eat infected food or water to contract it: Mares who carry the organism can pass it to their offspring during gestation. This means that EPM may be a possibility even in areas where opossums are not found.

This article first appeared in the July 2017 issue of EQUUS and re-published here with permission.