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Equine Infectious Anemia: Why do we test and why should you care?

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What is a Coggins test, and why is it so important? Why do I need a Coggins test if I am moving my horse(s) out of state or to an event? Why is the test only good for one year? This article will discuss the history of Equine Infectious Anemia and why it is a very important disease to keep under control. It will also discuss the route of transmission from one horse to another and the symptoms that a horse will have if it gets the disease.

Equine Infectious Anemia has been known by many names: Swamp Fever, Slow Fever, Mountain Fever, Equine Malarial Fever, and Coggins Disease, or EIA. It is a lentivirus from the family Retroviridae, and can infect all members of the Equidae family from ponies, donkeys, mules, and horses. EIA has been recognized as a disease of horses for centuries, but it made its big emergence in the 1930s and reached its height of devastation between the 1960s and 1970s. More than 10,000 horses were identified to be infected in 1975, and many of those horses died from the disease. Today the disease is less prevalent, and horses that do have the disease are nearly all-asymptomatic carriers of the disease, showing no signs of the disease. These horses act as reservoirs of the disease to spread to others.

The most common transmitting vector for EIA is biting flies, most commonly horse flies or deer flies. These flies lacerate the skin of horses to suck up a blood meal. The blood of an infected horse will remain on the mouth parts of these flies for a short period of time but long enough to be transmitted to an uninfected horse. Other ways of transmission is sharing hypodermic needles between horses, and it has even been found to be transmitted from mare to foal in utero.  Other minor routes of transmission can be from semen, milk and possibly be aerosolization of infectious material.

The clinical signs or symptoms of EIA are often nonspecific and usually the only sign is a fever. In severe cases horses will become weak, depressed, have increase heart rate and respiration rate, ventral edema, anemia, and bleeding from nostrils, and blood in their stools. Some cases will die during the acute phase of the disease, but those that recover will become asymptomatic persistently infected carriers. EIA is difficult to differentiate from other fever-producing diseases such as anthrax, influenza and equine encephalitis.

There is no treatment and no vaccines for EIA. The viral genome of EIA rapidly mutates, making it very difficult to create an effective vaccine to EIA.  Once a horse contracts EIA, the horse will always have the disease.

The only method to stop the spread of the disease is by prevention, and the only options to manage infected horses are to quarantine the infected horses at least 200 yards from healthy horses or to euthanize them. That is why testing is key to controlling the spread of this disease. Coggins testing is required once or twice a year depending on the state you live in, before traveling out of state, before entering an organized event, or sale of horses. It is always recommended to get a negative Coggins test before you introduce a new horse into a herd setting to maintain an EIA-free herd.

The Coggins test, developed in 1973 by Dr. Leroy Coggins, a graduate of Oklahoma State College of Veterinary Medicine in 1957, helps detect infected horses with EIA using the AGID method, or Agar Gel Immunodiffusion Assay. Dr. Coggins developed this test while studying viruses at Cornell University.  Today, the AGID test has been replaced mostly by the ELISA method. which is the most common test, used in reference labs around the country. The original method of testing of AGID is still considered the “gold standard” internationally.

If a horse is moved internationally they are required to get a Coggins test with the AGID method. A negative Coggins test is required before a health certificate is issued for travel. Generally most states require a negative Coggins test within one year, but some require it every six months. Veterinarians accredited by the USDA are the only veterinarians allowed to do Coggins testing and issue health certificates. Health certificates are issued to insure the horses that are traveling to events or crossing state lines are healthy and allow a level of traceability if a horse does become sick.  Most health certificates are issued for 30 days, but some are only issued for 10 days. A Coggins test requires hand drawn or digital images of your horse, identifying markings, address the horse resides, breed, age, sex, and owner’s information to complete the test. Today with a service called GlobalVetLINK hand drawn images are replaced with digital images uploaded into the Coggins form.

Luckily, with lots of hard work on behalf of veterinarians, laboratories, and state officials and due diligent horse owners, EIA is rather under control today, but there are still new cases of EIA discovered routinely. Also, there are many horses that do not receive testing, leading to possible reservoir of horses asymptomatically carrying EIA. Remember, even though it is sometimes inconvenient to get your horse’s Coggins test performed, you are doing your part to help control and prevent the spread of this terrible and incurable disease.

Read more great stories in the April 2020 issue of Oklahoma Farm & Ranch.

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Equine

What’s That Test For?

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By Ann Asher

For many horse owners, a Coggins test is part of the routine. If you’re headed to a horse show, rodeo, sale, boarding facility or across state lines, you have likely been asked for a current negative Coggins. The veterinarian draws a tube of blood, fills out the paperwork and, assuming the result comes back negative, the form goes in the file with the rest of the horse’s records.

But what are we testing for?

A Coggins test is a blood test for equine infectious anemia, commonly shortened to EIA. It is not a general test for anemia, and it won’t tell you whether a horse’s red blood cell count is low. The test looks for antibodies the horse’s immune system has produced against equine infectious anemia virus.

EIA is a viral, bloodborne disease that affects horses, ponies, donkeys, mules and other equids. The virus belongs to the lentivirus group, a family of viruses known for persistent infections. Once a horse contracts EIA, it stays infected for life. No approved vaccine prevents the disease, and no treatment eliminates the virus from an infected horse.

That lifelong carrier status is why the Coggins test matters so much.

Some horses with EIA become seriously sick. Clinical signs can include recurring fever, weakness, weight loss, swelling, depression and anemia. In severe cases, the disease can kill. Many infected horses, however, show few signs or none. A horse can look healthy, perform normally and still carry the virus, putting other horses at risk.

EIA spreads through infected blood. Horse flies and deer flies are important natural carriers. A fly can feed on an infected horse, get interrupted and move to another horse while blood remains on its mouthparts. Contaminated needles, syringes, surgical or dental equipment and anything else that moves blood from one horse to another can also spread the virus.

That’s why controlling EIA takes more than keeping flies away. Use a new sterile needle and syringe for every horse, and clean and disinfect any equipment that could become contaminated with blood.

The name “Coggins test” refers to the agar gel immunodiffusion, or AGID, test developed to detect antibodies to EIA. The test identifies antibodies against an antigen associated with the virus. Today, laboratories may also use approved ELISA tests, which return results faster. Because ELISA tests occasionally produce false positives, labs confirm positive screening results with the AGID, or traditional Coggins, test.

Keep in mind that the test looks for the horse’s immune response to infection rather than the virus itself, so timing can matter. A horse infected very recently may not yet have enough antibodies to test positive. Most infected horses eventually develop detectable antibodies, but there can be a window after exposure when the test comes back negative.

For the average horse owner, the larger purpose of routine testing is surveillance. Testing helps find infected horses before they unknowingly expose other animals.

In Oklahoma, horses attending equine exhibitions such as fairs, shows, rodeos and racetracks must have a negative EIA test from within the previous 12 months. Oklahoma also requires testing when horses mingle in common settings such as boarding and training facilities, as well as before most changes of ownership. Horses entering Oklahoma generally must have a negative EIA test from within the previous 12 months as well.

Those requirements can feel like one more piece of paperwork, especially for owners who travel often and have healthy horses that test negative year after year. But the system works because testing is routine.

There is no vaccine to fall back on if EIA starts spreading through a group of horses, and no cure for the infected horse. A confirmed positive animal remains a carrier for life and must be managed under strict regulatory requirements, generally through euthanasia or permanent isolation from other equids.

So when your veterinarian pulls that tube of blood for another Coggins test, the goal is bigger than getting the paper you need at the gate of the next event. We are looking for evidence of a lifelong, contagious disease that can hide in a healthy-looking horse. Finding those horses before the virus spreads makes that routine blood test one of the simplest and most important tools we have for protecting the horse population.

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Equine

A New Set of Challenges

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By OKFR Staff

By the time September rolls around in Oklahoma, most of us are more than ready for rain. After weeks or months of dry weather, brown pastures and hard ground, a good soaking rain can seem like the answer to a lot of problems.

For our horses’ feet, the end of a drought can bring a new set of challenges.

During long dry spells, hooves lose moisture and can turn hard and brittle. Dry weather is one of the factors associated with hoof cracks, particularly when combined with long trimming intervals or hoof imbalance. Horses traveling over hard, dry ground also take more concussion, and horses with thin soles or tender feet can grow sore as the ground hardens.

That makes regular farrier care especially important during a drought. You may be tempted to stretch the time between appointments because the feet don’t seem to be growing as fast, but keeping the hoof trimmed and balanced reduces stress on the hoof wall and the structures that support it.

Watch for small cracks and chips before they become big ones. Minor chipping around the bottom of an unshod hoof is fairly routine. A crack that keeps moving upward, gets deeper or causes lameness deserves a closer look from your farrier or veterinarian.

Then comes the rain.

After a long dry spell, hoof moisture can change quickly when horses start standing in wet grass, mud or saturated ground. Going from dry to wet and back again can contribute to brittle hoof walls and cracking.

Wet conditions bring other concerns. Long exposure to moisture can soften the hoof, particularly the sole and frog. Mud and dirty footing favor problems such as thrush and give bacteria more chances to enter through small cracks or separations in the hoof. Hoof abscesses also commonly follow swings between very dry and very wet conditions.

The best defense isn’t complicated. Pick up your horse’s feet regularly and pay attention to what you see and smell. Clean out packed dirt, manure and mud, and watch for cracks, tenderness, a foul odor around the frog or changes in the white line. Give horses a place where they can get out of the mud and stand on clean, dry footing.

Talk with your farrier before trying to change hoof moisture with frequent soaking or a lineup of topical products. More moisture isn’t automatically better. The goal is a healthy, balanced hoof that can adapt to its environment.

Finally, don’t ignore sudden lameness after the weather changes. A hoof abscess can make a horse dramatically lame, sometimes overnight. Many abscesses heal well with proper treatment, but sudden or severe lameness warrants a call to your veterinarian.

We can’t control when Oklahoma’s next rain arrives. Staying consistent with hoof care before, during and after that change gives our horses the best chance of handling it soundly and comfortably.

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Equine

More than Just a Saddle Pad

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By Savannah Magoteaux

Walk past the horse trailers after a summer jackpot, ranch rodeo or trail ride, and you’ll probably see the same thing: saddle pads draped over gates, fences and trailer doors, drying in the afternoon sun. Some are soaked through with sweat. Others are already stiff with dried salt, caked hair and arena dust.

It’s easy to think of a saddle pad as one more piece of tack, but it has one of the hardest jobs on your horse. On every ride, it cushions the saddle, helps spread pressure across your horse’s back, absorbs sweat and lets heat escape.

A quality saddle pad can last for years if you take care of it.

Built-up sweat, dirt and hair shorten the life of a pad. Over time, they also compress the fibers, reduce the pad’s ability to wick moisture and create stiff spots that can rub your horse’s back. Even the best-made pad can’t do its job once it’s hard as a board.

One of the simplest habits you can develop is cleaning the pad after every ride. Knock off loose dirt, brush away hair and let the pad dry completely before putting it back in the tack room or trailer. Storing a damp pad invites mildew, odors and bacteria and breaks down many materials over time.

Every saddle pad serves the same basic purpose, but the material determines both how it performs and how you should care for it.

For many western riders, wool felt remains the standard. One of its greatest advantages is that it gradually conforms to the horse’s back without losing its structure. To care for a wool felt pad, remove hair with a curry comb or stiff brush after each ride and let it dry thoroughly. When it needs a deeper cleaning, use cool water and a mild wool-safe detergent if the manufacturer recommends one. High-pressure washers, harsh detergents and excessive heat can damage the wool fibers and reduce the pad’s performance.

Traditional woven wool blankets are still popular, particularly beneath ranch saddles or as a top blanket over a felt pad. Shake them out regularly, brush them clean and wash them gently when necessary. Most should air dry, since a dryer can shrink natural fibers.

Neoprene pads have become common because they’re durable, lightweight and easy to clean. Unlike wool, neoprene doesn’t absorb moisture. Many neoprene pads have textured or waffle-patterned surfaces that help move sweat away from the horse while letting air flow beneath the saddle.

You can rinse most neoprene pads with a hose after riding and wash them with mild soap now and then. Let them dry completely before storage, and keep them out of intense heat and direct sunlight, since neoprene can turn brittle over time.

Foam, gel and memory foam inserts show up in many performance pads designed to add shock absorption or relieve pressure points. These materials can cushion well, but many hold more heat than wool. Care varies considerably from one manufacturer to another, so follow the cleaning instructions that came with the pad instead of assuming all synthetic materials wash the same way.

Synthetic fleece pads are another common option, particularly for everyday riding. They are generally easier to clean than natural wool, and many can go through a washing machine on a gentle cycle before air drying. Regular brushing between washings keeps the fleece from matting and packing with hair.

Whatever type of saddle pad you choose, no pad can make up for a saddle that doesn’t fit. Even the thickest pad cannot eliminate pressure points created by a poorly fitting saddle. Think of the pad as a partner to proper saddle fit, helping protect your horse while the saddle does its job.

Before your next ride, flip your saddle pad over and run your hand across the side that rests against your horse. If it feels rough, stiff or crusted with dried sweat and hair, imagine how it feels after an hour in the saddle.

A few minutes spent cleaning and drying your pad after each ride will help it last longer, protect your investment and keep your horse more comfortable every time you swing a leg over.

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