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Equine

The Importance of Equine Vaccinations

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By Lauren Lamb, DVM, MS

Vaccinating horses is crucial to overall health maintenance and essential to responsible ownership. It is important to protect the horses against diseases they could be exposed to whether they travel or stay at the stable or farm.

The number of diseases a horse is exposed to is directly proportional to the number of vaccinations necessary to ensure adequate protection. Horses that live a more isolated lifestyle will be exposed to a lower number of diseases and will need to only receive the core vaccinations. On the other hand, a horse that is showing and traveling is exposed to a greater number of diseases. These horses need to receive the core vaccinations plus additional vaccinations due to increased risk.

Another consideration when deciding which vaccines to administer to a horse is treatment costs versus vaccination costs and following boosters.

A good example of this scenario would be the rabies vaccination, which is relatively cheap. A rabies vaccinated horse is not 100 percent protected from the disease. However, the risk of the horse developing the disease if exposed is significantly decreased. The flip side of the coin would be if you did not vaccinate your horse for rabies, which leaves them at significant risk of developing the disease if exposed.  This is compounded by the fact that there is no treatment for a horse with rabies.

Vaccines can be divided in to four large groups based on how they are made and how they work when administered: live vaccine, modified live vaccine, recombinant vaccine and killed vaccine.  They all contain antigens, parts of the disease-causing organism, that will train the immune system, but they will not cause a clinical disease in a horse.

Live and modified live vaccines are capable of inciting an immune response most like the natural occurring disease without causing the horse to develop the disease. Because they cause such a strong immune response, a booster vaccine does not need to be administered as frequently as the recombinant and killed vaccine. It is very important to administer live and modified live vaccines as directed on the label. Failure to follow labeled directions can result in significant complications or decreased efficacy of the vaccine.

Recombinant and killed vaccines incite an immune response that is sufficient to protect the horse from disease, but less like the natural disease compared to the live and modified live vaccine. Recombinant and killed vaccines require more frequent booster vaccinations, due to the less natural response to these vaccines. Deciding which vaccines to use depends on what vaccines are available and a local veterinarian’s recommendation.

All vaccines are given to a horse with the goal of the horse mounting an immune response to the vaccine. This immune response trains the horse’s immune system to recognize certain characteristics of the disease-causing organism, which in most cases is a bacteria or virus. The horse’s immune system can then react in a timely and aggressive manner that will rid the body of the disease. Without the prior vaccination, the horse’s immune system may not react to the inciting organism in a timely manner, allowing the disease to be established in the horse.

The American Association of Equine Practitioners established guidelines and recommendations for vaccinating horses depending on the level of exposure to diseases, age and pregnancy status.

Eastern and Western Equine Encephalitis, West Nile Virus, Rabies and Tetanus are the core vaccines that each horse living in North America should receive. The core vaccines are based on the high risk of any horse living in North America being exposed to one of these disease. These vaccines provide a very high level of protection but not 100 percent.

Eastern Equine Encephalitis, Western Equine Encephalitis and West Nile Virus are all viruses that affect the horse’s central nervous system. They cause clinical signs of dullness, depression, muscle fasciculation or ataxia. They are all spread by mosquitoes and are seen more commonly in the summer months when the mosquitoes are more prevalent.

Eastern Equine Encephalitis is more commonly seen in the eastern portions of North America and WEE is seen in the western portion of North America. West Nile Virus can be seen in all regions of North America and is the leading cause of encephalitis cases in horses. Horses that have WNV, EEE or WEE have a fair to poor prognosis.

Rabies is a virus that a horse contracts by being bit by another rabid animal. The virus migrates from the bite wound up the peripheral nerves and attacks the horse’s central nervous system. As stated before, no treatment currently exists for rabies.

Tetanus is a disease caused by a neurotoxin that is produced by Clostridium Tetani bacteria. This bacterium is found everywhere in the environment. Once the bacteria gains access to a wound, it will replicate and release the neurotoxin into the horse’s body. If a horse contracts tetanus, there is a guarded prognosis for recovery.

Risk-based vaccines are vaccines that are administered based on the horse’s level of exposure to a disease. Three commonly used vaccines in our practice are Strangles, Equine Influenza, and Equine Herpes.

Strangles vaccine works against the Streptococcus equi subspecies equi bacteria and helps prevent or limit the strangles disease in a horse. It is usually administered to young horses in environments known to have the strangles bacteria present.

Equine Influenza and Equine Herpes are both respiratory viruses that can be spread by aerosolized respiratory droplets. They are extremely contagious and are seen in locations with a high number of horses from many different locations including large horse shows. Consulting a local veterinarian about which vaccines would be prudent given its level of exposure is recommended.

The frequency that a horse should be vaccinated depends on several factors including age, vaccination history and pregnancy status. In general, EEE, WEE and WNV vaccines should be administered in the spring before the mosquito season starts. Most veterinarians will administer the remainder of the core vaccines at this time. Risk-based vaccines may need to be given more frequently depending on the level of risk that the horse is exposed to.

The bottom line is, consult with your veterinarian and develop a vaccination program that works for you and your horse.

For more information on equine vaccination, visit www.aaep.org. The AAEP website provides horse owners with detailed information about core and risk-based vaccines.

This article originally appeared in the January 2016 issue of Oklahoma Farm & Ranch. 

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Equine

Here’s to the Great Horses

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By Summer McMillen

Everyone that knows anything about horses knows that there are bad ones, good ones, and great ones.

The bad ones are good for nothing. You can’t catch them, you can’t saddle them, and you can’t get on them without feeling like you need a helmet, some kind of padded vest and, an instruction manual. Once you do mount up the whole ride is a battle and heaven forbid, you actually have a job to do because they are little to no help in holding the herd. We all find ourselves owning a bad one or two throughout our lives. Best case scenario is they find a more tolerable home to go to through via a horse sale or the classifieds. Worst case scenario all you can do is say “Vaya con Dios,” put a sign on them that reads “Do Not Attempt,” and turn them out to pasture. Hoping they are decent enough to stay within the borders and make a beautiful yard ornament.

Good horses are usually much more tolerable. They’re pretty easy to catch, saddle, and hop up on. Sometimes they might have a bad habit or two like setting back when they’re tied to a fence or, getting cold backed on early mornings that you tolerate because they are so skilled in a specific field. A good horse is usually only good for one thing. They have a niche talent m, if you will. They can be a good heel horse. A good head horse. The horse you want to gather pastures on because you know he won’t knicker or rare up when you get dropped off in the jig line. A good kid horse. Your rodeo horse. The horse you put your wife on when she’s being a little wimpy that day. Good horses usually get sold because they are proficient in their given field and they find good homes making both parties happy. We will all own many good horses in our lives and be happy to do so.

Great horses are a rare and treasured possession. They are simultaneously easy and hard to own. Easy because you can do anything on them. Hard because everyone is always trying to buy them from you. A great horse stands still while your kid pulls their head down all the way to the ground so they can halter them. A great horse is never cold backed and always ready to cinch tight and take off. A great horse can be ridden in the pasture and the rodeo arena on the same day. A great horse doesn’t need practice. A great horse is always willing to do anything you ask of them at any given moment. Great horses find their homes as horse colts and usually live out the rest of their days at the same home because great horses are irreplaceable.

People and horses are not all that different. There are bad, good, and great ones. The more time I spend around horses the more I am convinced of the kind of person I want to be. “Bad” will absolutely not do. “Good“ is much too common  and just doesn’t quite cut it more often than not. “Great” is what I aspire to be.

Great can be defined in so many ways when we let human standards get involved but, I want to be great as defined in the qualities of a great horses.

I want to be kind and patient while my children are learning. I want to be ready to help anyone who asks me. I want to go the extra mile. I want to make my home a beautiful place to come to after a full day’s work outside. I want to not be thrown off by life’s twists and turns but, firm in my faith.

So, basically what I’m saying is I want to be a great horse. And honestly there are worse things we could all aspire to be.

Here’s to great horses. May we know them, love them, and if we’re lucky be great just like them.

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Equine

Degenerative Suspensory Ligament Desmitis of the Horse

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By Dr. Garrett Metcalf

The suspensory ligament is a vital component of the limb of a horse to produce normal locomotion and support. The suspensory ligament is a common area of concern in performance horses of various disciplines and can be single handedly the cause of lameness or performance issues. This article is going to look at a specific degenerative disease of the suspensory ligament and what horses are at risk for this disease.

DSLD or degenerative suspensory ligament desmitis was first discovered in the early 1980’s in Peruvian Paso horses. The name has been changed because the suspensory ligament is not the only organ affected from the disease but the suspensory is ultimately the biggest issue. The newer name, ESPA or equine systemic proteoglycan accumulation, is more correct because other ligaments and tissues are affected by this disease. In this article we will only focus on the suspensory ligament. The most commonly affected breeds are Peruvian Paso, Paso Fino, Morgan, Saddlebred, Warmblood, Paints, American Quarter Horse, and Thoroughbred breeds. The age of onset of the disease is variable among breeds but it is more common to be seen in middle age to older horses.  However it has been documented in horses as young as one year of age. The disease generally will have a slow insidious onset that can go undiagnosed for months or years depending on the horses work and discipline.

A horse that begins to show early signs of DSLD may have a vague lameness issue that is difficult to isolate and they most likely will resolve with a period of rest. As the horse returns to moderate level of work the lameness will return. This scenario may go on for several months or more before the discovery of the DSLD is made. The first indication of DSLD is often pain isolated in the suspensory branches or fetlock region when a flexion test is performed. Horses with DSLD will also have a “dropped” fetlock appearance because the suspensory is the main supporting structure of the fetlock joint.  DSLD can affect the hind limbs, forelimbs or all limbs at the same time. A unique sign of DSLD is that not just one limb is affected but rather bilaterally affecting the limbs, meaning it will either affect either both forelimbs or hind limbs at the same time. It is my experience that the hind limbs are more commonly affected compared to the forelimbs. Horses will often have enlargement of the fetlock region and increased joint fluid or wind puffs. Horses will often have a straight hock or post legged hind limb appearance. Horses will often shift weight frequently in an effort to get relief from the discomfort and this can be confused with other lameness issues or foot related pain.

Diagnosis of DSLD is often made by clinical signs, breed and ultrasound findings. Ultrasound imaging of the suspensory ligaments will often show diffuse enlargement of the suspensory body and branches. The suspensory ligament will have a poor heterogeneous fiber pattern with periligamentious soft issue thickening from scar tissue deposition and edema or fluid within the tissue.  Radiographs of the lower limb may reveal abnormal bone changes in the sesamoid bones behind the fetlock joints and even osteoarthritis of the pastern and or fetlock joints. A definitive diagnosis can be made from a biopsy of a ligament in the neck called the nuchal ligament, but is not often performed because of the invasiveness of the biopsy.

Treatment is very limited and it is mostly geared towards protection of further damage by prolonged rest. Pain management is also important to attempt to keep the horse as comfortable as possible. Different shoeing techniques can be used with marginal success. In early cases of DSLD, a suspensory shoe that helps engage more work from the deep digital flexor tendon can help elevate the fetlock and offer more protection to the suspensory ligament. The devastating thing about this disease is that there is no cure and there are hardly any good options to slow the progression of the disease. DSLD carries a poor prognosis when the diagnosis is made in any breed of horse or any discipline. Although some cases can be managed better than others, it often progresses to the point of debilitating pain and discomfort to the point of humane euthanasia especially in the Peruvian Paso breed.

Read more in the February 2023 issue of Oklahoma Farm & Ranch.

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Equine

Gastric Ulcers

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By Dr. Devan England DVM

Does your horse have gastric ulcers? Gastric or stomach ulcers are frequently blamed for a variety of things including poor performance, acting ‘cinchy’, weight loss, not eating, poor coat condition, diarrhea and colic. However, gastric ulcers are not always the culprit and the only way to know for sure if your horse has gastric ulcers is to look at the stomach on camera, using an endoscope. Poor appetite and poor body condition are the mostly widely observed clinical signs with gastric ulcers, however, these are non-specific. If you think your horse might have gastric ulcers, the best place to start is to talk to your veterinarian and consider scheduling a gastroscopy. Gastroscopy requires the horse be held off feed for at least 16-18 hours and held off water for at least 6-8 hours. Fasting off feed and water is necessary to allow the veterinarian to see the whole stomach. If restricting feed or water is difficult in your management situation, many veterinarians will allow you to hospitalize your horse the night before gastroscopy for proper fasting.

Gastric ulcers are split into two types, classified by the location of the ulcer in the stomach. Squamous ulcers are ulcers that occur in the squamous or skin like portion of the stomach. This is the top part of the horse’s stomach, is closest to the esophagus, and has squamous tissue to protect this portion of the stomach from stomach acids. The other ulcer type are glandular ulcers. Glandular ulcers occur in the bottom portion of the stomach, which is closest to the small intestine. This portion of the stomach has glandular mucosa with cells responsible for producing stomach acids for digestion as well as cells that produce mucus and buffers to protect the lining from stomach acid. Gastroscopy is important not only for diagnosing whether ulcers are present but also determining the severity and the type of ulcer, because these two ulcer types require different treatments.

Squamous gastric ulcers are common in racehorses both in and out of training, with higher prevalence in racehorses under training. Prevalence in Thoroughbred racehorses in training has been reported to be up to 100% (Sykes 2015). Squamous ulcers are also prevalent in Western pleasure horses, Thoroughbred stallions on breeding farms, and Italian donkeys (Sykes 2015). Glandular gastric ulcer prevalence has not been as well described as squamous ulcers. Glandular ulcers are reported to be most common in Thoroughbred and Standardbred racehorses, Canadian showjumpers and polo ponies, and American Quarter Horses (Sykes 2015).

Risk factors for ulcers vary by ulcer type. Anti-inflammatories (Bute, Banamine) can increase the risk of glandular ulcers in some horses by affecting normal defense mechanisms but are not a high risk in most horses. Horses that display stereotypic behaviors, such as cribbing, have an increased risk of squamous ulcers. Grain fed before hay in non-exercising horses, feeding larger amounts of grain, and increased time between meals increases the risk of squamous ulcers. Increased time with high intensity exercise and housing in single pens is associated with increased risk of glandular ulcers. A straw only diet, lack of water access and lack of direct contact with other horses increases the general risk of gastric ulcers.

If your horse is diagnosed with ulcers, the mainstay of treatment is a buffered formulation of omeprazole (Gastrogard, Ulcergard). Over the counter Omeprazole and compounded Omeprazole are not effective because without buffering, the acidic stomach quickly breaks down the drug before absorption. Most horses with squamous ulcers will have healing of these ulcers after a 4-week course of Gastrogard or Ulcergard at treatment dose (whole tube for the average horse). Some horses may be healed by 3 weeks of treatment, but all horses should undergo a recheck gastroscopy before stopping treatment. Horses diagnosed with glandular ulcers need combination therapy with Gastrogard/Ulcergard and Sucralfate for 4 weeks. About 2/3 of horses with glandular ulcers will heal in this time, but some horses may require longer treatment times so a recheck is always recommended before discontinuing treatment.

Horses at higher risk of gastric ulcers may benefit from preventative (low) doses of Ulcergard (1/4 tube in average sized horse) given for a few days before and during high stress situations like long distance travel and competitions. Sea buckthorn berry supplement may be protective against formation of glandular ulcers. Dietary management to decrease the risk of ulcers includes providing more frequent small hay meals if pasture access is not available, limiting high sugar grains as much as possible and adding vegetable oil to the feed.

Sykes BW, Hewetson M, Hepburn RJ, Luthersson N, Tamzali Y. European college of equine internal medicine consensus statement – equine gastric ulcer syndrome in adult horses. J Vet Internal Med 2015; 29:1288-1299.

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