What You Need To Know About Stringhalt In Horses

My horse has a severe over flexing problem in its hind limb. It is noticeable when it is trotting or walking, but when it attempts to turn on the limb affected or back up slowly it becomes extremely evident. If my horse becomes startled suddenly it is also apparent.

Stringhalt is a painless gait abnormality in which the tendons of one or both hind limbs of a horse suddenly flex upward with each stride. If this condition is left untreated it can cause the horse to not be able to walk normally.


What is the Condition of Stringhalt in Horses?

Stringhalt is a painless neuropathic condition that causes the horse’s tendons to contract excessively when the horse is walking so much so that its leg will draw up and hit its abdomen. It will also dangle its leg in the air a lot more than usual when compared to a nonaffected gait. When it lowers its leg, it will also slap the ground, with its hoof landing hard and flat.

Stringhalt is characterized by its unusual hindlimb gait which you will definitely notice as your horse walks forwards or backward.

At first, I was under the impression that my horse had symptoms like locking patella, shivers, EPM (Equine Protozoal Myeloencephalitis), or Stifle.

To be sure, let’s now look at the differences between Stringhalt and Shivers below.


What Is Shivers?

Shivers and Stringhalt are very similar in the fact that both conditions involve the tendons that are in the hind limb flexing upward when walking forward or when walking backward. With Shivers the muscles also quiver and the tail is raised while the abnormal gait is going on however when the horse lowers his affected limb it doesn’t slap it hard on the ground as it does when the horse is affected by Stringhalt.


Stringhalt – The History

Stringhalt or Equine Reflex Hypertonia was first reported in horses and other hooved animals going as far back as the Renaissance years. The condition could have, however, existed before then and not been reported. Its main characteristic is an extreme contraction of the tendons of the lower limbs when there isn’t any pressure against the muscles.

What You Need To Know About Stringhalt In Horses

What Are the Clinical Signs of Stringhalt in Horses?

The first thing you’ll notice is that your horse will use its hind leg to hit its abdomen and then will quickly put its affected leg down hard so it slaps the ground. You will definitely notice this when the horse is turning or when it is rearing up. It normally only affects one hind leg but both could be affected, and –very rarely – all four limbs could be affected.


What Causes Stringhalt in Horses?

Stringhalt is a condition that is neurological as it is caused by nerve damage. The sensory receptors detect muscle changes and cause the muscle to contract however some of the muscles will not contract the way that they are supposed to. Due to the nerve damage, they may contract too soon or much later at times when the horse is moving. This is an indication that the neurological disorder is caused by a form of toxicity. This can cause such an abnormal gait in the horse that the animal can become so seriously handicapped that it may have to be euthanized.


What Are The Different Stringhalt Types

Stringhalt in horses is divided into two categories: Australian Stringhalt or Pasture Related Stringhalt as it is sometimes referred and Classic Stringhalt


What Is Australian Stringhalt?

Australian Stringhalt is caused from the horse ingesting toxic plants such as two types of Cheeseweed (Little and Common Mallow), Flatweed is technically known as Hypochoeris radicata ( Cat’s Ears or False Dandelion) and the Taraxacum Officiale also know as the Common Dandelion. Other plants have also been linked to Stringhalt or Stringhalt like symptoms these are Lathyrus species (Sweet pea), and Malva Parviflora or Mallow.

Flatweed, however, seems to be the main culprit which normally causes Stringhalt. Usually, these weeds aren’t toxic to the animal but their toxicity levels can rise under environmental circumstances. They will increase during the colder temperatures and decrease when the temperature rises. This type of Stringhalt will affect both of the horses’ legs, but if the condition is severe enough then all four legs can become affected. Poor drought scarred pasture land has also been cited as a factor.

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Once the horse stops consuming these toxic plants it may recover but it will take time. Brazil had two such outbreaks of Stringhalt and Jose Allan Soares de Araujo a veterinary hospital researcher conducted an experiment in which a young horse was fed with flatweed.

After ingesting it for three weeks the horse began showing signs of Stringhalt but when the plant was removed from its diet its symptoms improved. This proved the researcher’s theory that flatweed was causing the problem.

This is why it is imperative to keep a close eye on what your horse is eating when you see signs of Stringhalt in your horse. You then need to remove the offending weeds from its area. It is also necessary to provide the horse with a quality diet and some laxatives for help in flushing out their gastrointestinal tract so that further absorption of the plant’s toxins will be prevented.


What Is Classic Stringhalt?

Plant toxicity is not linked to Classic Stringhalt. It stems from an injury to the horse’s neck or back however its cause is still uncertain. In all likely cases, the clinical symptoms will improve when the injury heals.

The horse will suddenly jerk its leg upwards towards its abdomen and then will drop that affected leg back to the ground hard. The abnormal movement usually starts out mild but will become more violent over time because the injury becomes progressively worse or when the horse is experiencing pain from the rear foot which could stem from its stifle (knee) or hock.

At other times there no obvious injury may be diagnosed at all which makes it harder to figure out what is causing Stringhalt to occur. When this happens your vet may consider other causes such as a common developmental disease affecting the cartilage at the joints known as Osteochondritis Dissecanns (OCD). Other causes may also be considered such as Arthrosis (a non-inflammatory degenerative condition associated with aging) or Arthritis often called Degenerative Joint Disease (DJD) in which the joint or cartilage wears down resulting in pain for the animal and eventually causing it to become lame. It would be unwise to continue vigorous training or strenuous work, as both of these would cause the condition to become much worse.What You Need To Know About Stringhalt In Horses

If this scenario is the case then your horse’s condition would only continue to become progressively worse as the disease will continue deteriorating the joints as it spreads from one affected rear leg to the other and eventually to all four legs. Sadly, your horse might never recover if this is the situation.

There are some treatments available though. These include surgery, muscle relaxants, anticonvulsant drugs, and Botox. This doesn’t mean that your horse will make a full recovery though. You should not ride your horse or do any kind of tricks with it during this time.

Your horse will need an in-depth neuromuscular exam if it is ridden or used frequently. A horse inflicted with Stringhalt shouldn’t be ridden as it poses a dangerous risk to the rider.

What Is The Diagnosis?

A veterinarian for horses who have specialized in neuromuscular development would be able to accurately assess the Stringhalt symptoms. If a horse is suffering from Australian Stinghalt a thorough diagnostic exam isn’t needed merely evaluating the feed or grazing pasture that the horse is using to be sure none of the toxic weeds are present.


What Happens At The Orthopedic Exam?

When the equine veterinarian examines your horse a series of tests will be performed which will include ultrasounds and the affected limb X-rays or limbs to see the condition of the hock, tendons, and muscles. The vet will also check the horse’s reflexes and can detect any abnormalities with a nervous system that increases tone in the muscles when the horse moves.

There are a few conditions that may become evident at the time of the orthopedic exam. One condition is known as Hypertonia. This condition causes uncontrollable muscle spasms, abnormal muscle tone, a stiffening of the muscles or straightening out of the muscles and shock-like contractions of a muscle or a group of muscles in the limbs. Another condition that may become evident is called Hypermetria that causes the muscles to have an increased range of motion but a lack of direction. Since these neurological problems consist of a vast array of complicated symptoms and causes for them an extremely thorough neurological exam must be performed.

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Sometimes it is necessary to have a more advanced series of testing done by the specialist. Other infectious muscle diseases should be ruled out as a factor for the cause of Stringhalt. One such disease is equine Protozoal Myeloencephalitis (EPM) which is an infectious disease caused by the parasite Sarcocystis neurona which will cause ataxia and muscle spasticity.

The second disease although not infectious that would be tested for is called Polysaccharide Storage Myopathy (PSSM) which is an inherited condition that causes a horses muscles to be unable to properly store sugar (glucose) so that it isn’t available for the horse to use when it needs to do so.


What Diagnostic Process Is Involved?

Sometimes a horse will be required to be hospitalized so that it can be observed for several days. These tests could include diagnostic imaging, orthopedic tests, and electromyography (EMG’s). This diagnostic test is used to check the health of the muscles and the motor neurons (nerve cells) that are responsible for controlling them.

This test can reveal several things such as muscle dysfunction, nerve dysfunction or if there is a problem with the nerve to muscle signal transmissions.these tests can offer up a more thorough and accurate diagnosis. When EMG is used it gives the veterinarian a very clear picture of what is occurring with the muscles which would eliminate any confusion when figuring out an effective treatment for the afflicted horse.


What Are The Treatments For Stringhalt?

When Stringhalt is due to the horse ingesting toxic plants such a problem can be easily fixed by simply removing the horse from that particular grazing pasture to another pasture free from the toxic weeds. The afflicted horse will be given vitamin B complex and magnesium salts to help with its peripheral nervous system symptoms.

On average a horse given this treatment will usually recover in anything up to nine months or in some cases, the recovery time is less. If however, the horse is suffering from an extreme Stringhalt in which all four limbs or both legs are affected then the recovery time could be longer. If this situation is the case then the treatment will be given again.


Relaxing the Muscle

The veterinarian will prescribe muscle relaxants if your horse has a persistent Stringhalt problem. Muscle relaxants work on the horse’s nervous system. Botox or the Botulinum toxin will be used to alleviate the clinical signs of Stringhalt.


The Use Of Anticonvulsants

Anticonvulsants may be relied on to give your horse relief from their Stringhalt symptoms if they are suffering through a particularly severe stage. They help to normalize the way that nerve impulses travel along the nerve cell path. Since these are sedatives they only provide horses suffering from the symptoms of temporary relief.


The Use Of Phenytoin

Phenytoin or Dilantin as it is also known in some quarters as an anti-seizure medication. It is given to a horse to manage and treat Australian Stringhalt. Horses can be given either intravenously (IV) or orally to prevent a partial seizure (focal seizure) and a grand mal seizure (tonic-clonic seizure).

The horse dealing with Australian Stringhalt may show a significant improvement in their movement when given Phenytoin. The Phenytoin will be mixed with the horse’s feed at rates of 15mg/kg every 12 hours over two weeks.

When giving Phenytoin, the goal is to be able to reduce the clinical indications of Australian Stringhalt. The Phenytoin changes the cells membrane potential to make it more negative. When this occurs the impulses from the horse’s nerve membranes are slowed down so the spasms and contractions will stop. Long term treatment for horses suffering Stringhalt is expensive and can also be risky. If the horse suffering from Stringhalt is a racehorse it will make the horse test positive for the presence of drugs.


Using Surgery To Help To Alleviate The Signs Of Stringhalt

A surgical procedure exists which would cut through the principle tendon of the muscle and divide the muscle either in half or partway through. This procedure is called Myotenectomy. Another procedure that can be done is called a Lateral Digital Extensor Tenectomy. This surgical treatment would remove some of the tendons of the lateral digital extensor which crosses the lateral surface of the hock joint. There is no guarantee of success with this and sadly the inflicted horse might not ever recover fully.

However, in the vast majority of cases, the surgery helps to alleviate the clinical signs of Stringhalt and the afflicted horse may begin to move normally.

Some Frequently Asked Question About Stringhalt:

Is there a Cure for Stringhalt In Horses?

Since Australian Stringhalt in horses is mainly attributed to toxic weeds that the horse has eaten out in its pasture land then the horse can get back to full fitness some six to nine months after the offending weeds are removed or the horse is transferred to a new pasture without the toxic weeds inhabiting it for the horse to feed on. However, in the case of Classic Stringhalt it may or may not be cured depending upon the severity of the case. In other words the more severe the case the less likely it is that that it will be cured.

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It is possible to use the Botulism toxin or Botox to help retrain the affected horse. Botox will help the horse in the short term to manage any neurological issues it is having.

It is also possible for the horse affected with Stringhalt to have a good quality of life. It may not, however, return to the state it was in before having the condition. It is also entirely possible for the horse to develop a relapse. It is entirely possible too that a horse who exhibited severe clinical signs can go on to recover fully and proceed to carry on with its normal activities and resume its normal life.

Scientists are working hard to further understand Stringhalt and how it occurs in horses by performing a necropsy or a post- mortem examination on horses that have died from Stringhalt. They are also continuously doing research into this debilitating neurologic disease.

Since the Botulism toxin or Botox has been used in humans to smooth out the wrinkles in the face scientists are using it to help resolve clinical indications of Stringhalt in the horse. During this research the scientists have noted a level of success and are keen to see it used in higher doses, hoping that it will reduce any observed Stringhalt symptoms in horses.


Is It Possible That Stringhalt Could Be Genetic?


Since all breeds of horses are susceptible to Stringhalt there have been no obvious genetic links associated with Stringhalt. It has been most evidently seen in horses who are around the ages of four or five years old. This finding has led many scientists to speculate that there could be a genetic predisposition for it. If there are specific correlating factors, Stringhalt has numerous causative elements thereby making it extremely difficult to be able to connect it solely to genetics in its entirety.What You Need To Know About Stringhalt In Horses

Furthermore, what causes Classic Stringhalt is very unclear, but it believed that it could be, in part, a result of a traumatic injury which results in damage to the sensory nerves that are in the muscles of the horse’s hind limbs.


Can A Horse Suffering With Stringhalt Be Safely Ridden?

Stringhalt causes a hopping type of gait that is an indication that the Stringhalt that the horse has is severe. While some horses are still able to work or perform without any impairment the horse is still technically considered not safe or in poor condition.

While Stringhalt does not point to the pain a horse might be in, it may appear so, but the horse is not in pain. It may not even appear to be uncomfortable even, but it is still not advisable to mount it or to have it perform any type of riding or obedience, flexibility or balance training.


Final Thoughts on Stringhalt In Horses

When a horse displays any external indication of Stringhalt it is basically a sign that the horse has a neurological disease that it is suffering from. The origin of the Classic type of Stringhalt is unknown still. The Australian type of Stringhalt is caused by the horse ingesting weeds that are toxic such as false dandelion or flatweed or cat’s ear.

When a horse has this condition it will draw one or both of its hind limbs up to its abdomen and pause with them there irrespective of what it is doing – walking, trotting, backing up or turning. This means that Stringhalt is an exaggerated movement that the horse cannot control. When the horse is removed from the pasture where the toxic weeds are the horse’s symptoms may clear up within a few days to a few month’s time. In addition, a diet that is high quality and should be offered to the horse to help speed up its recovery process.

If the symptoms of Stringhalt still persist the horse may still need additional treatment. This could include anticonvulsant drugs such as Phenytoin or in worse cases, surgery to remove the tendons that may be necessary. Nearly all the treatment procedures that are required are very costly for the owner and risky to the horse and there is also no guarantee that a full recovery will be made by the horse. There is also a chance that if the horse does recover it can have a relapse as well.