Stringhalt in Horses

What Is Stringhalt in Horses?

Stringhalt in horses, also called springhalt, is a condition in horses that refers to an abnormal hindlimb movement.

Stringhalt causes one or both horse hindlimbs to flex suddenly and violently toward the abdomen and then jerk back to the ground in one quick motion. Stringhalt in horses is relatively common, but due to the majority of cases being unreported by horse owners and veterinarians, a true statistic of occurrence is unknown. Stringhalt can affect any horse regardless of breed or age.

There are two distinct stringhalt conditions in horses: classical and bilateral.

• Bilateral stringhalt—also known as Australian stringhalt. It affects both hindlimbs and is typically seen in outbreaks, meaning multiple horses are affected at the same time. Despite being called, “Australian” stringhalt, it is reported worldwide.

• Classical stringhalt—usually affects only one hindlimb and occurs in isolated cases. This type of stringhalt is also reported worldwide.  

Symptoms of Stringhalt in Horses

• Mild to slightly jerky gait

• Extreme hyperflexion of hindlimb

• Hindlimb muscle atrophy

• Bilateral stringhalt may have “bunny hopping” gait

• Occurs while walking forward, backing up, or turning

• Most or every stride in the horse affected

• Made worse by excitement, cold weather, or hard exercise

If your horse is exhibiting any of the above symptoms, contact your veterinarian.

Causes of Stringhalt in Horses

Bilateral Stringhalt Causes

Bilateral stringhalt in horses is caused by ingestion of a toxic plant. Plants commonly associated with bilateral stringhalt include:

• Flatweed

• Fireweed

• Mustard weed

• Dandelion

Ingestion of these types of plants most often occur at the end of summer when horses may graze dried out pastures. An unidentified toxin in these weeds affects the long nerves in the horse’s body. The toxin damages the outer layer of the nerve cell, preventing the nerves from transmitting information from the brain to the muscle appropriately.

Scientists have tried to determine the exact toxin and how much of it is necessary to cause symptoms of stringhalt, but have been unable to provide clarity at this time. Complicating matters, individual horses may have different levels of susceptibly to the toxin and plants have variable concentrations of the toxin. 

Classical Stringhalt Causes

A definitive cause of classical stringhalt in horses is unknown at this time. Classical stringhalt sometimes occurs after an injury to the hindlimb or as a secondary result of equine protozoal myeloencephalitis (EPM) or equine motor neuron disease (EMND).

Additionally, foot conditions like hoof abscesses and arthritis in the hock have been associated with the development of stringhalt in horses. Depending on the underlying cause of the condition, the clinical symptoms can be the result of mechanical effects, like adhesions, interference in limb reflexes, or a pain response.

How Veterinarians Diagnose Stringhalt in Horses

Veterinarians will rely solely on their physical exam and history to make a diagnosis of stringhalt. Once other conditions, such as arthritis or an abscess, are ruled out, stringhalt is diagnosed based on the characteristic jerky gait seen on the physical exam.

Electromyography (EMG), a diagnostic procedure that can measure the muscles’ response to a nerve stimulation, may be helpful in supporting a diagnosis of stringhalt and documenting abnormal nerve function, but it is not necessary to make a diagnosis.

Horses with both classical and bilateral stringhalt will have no abnormalities on routine blood work. Since the exact toxin in bilateral stringhalt has not been identified by scientists, a specific blood test for the toxin is not available.

Treatment of Stringhalt in Horses

Treatment for Bilateral Stringhalt in Horses

Cases of bilateral stringhalt are treated by removing horses from access to the toxic plant. During the recovery time, make sure your horse has access to clean, fresh water and either a good source of hay or access to an uncontaminated pasture. Additionally, keep up good horse husbandry and foot care.

Treatment of Classical Stringhalt in Horses

It’s important to look for and treat any other sources of pain (arthritis, recent hoof shoeing/trimming, or a hoof abscess) in a horse before embarking on a treatment of stringhalt.

Medical Treatment of classical stringhalt:

• Muscle relaxers

  • Methocarbamol

  • Mephenesin

  • Baclofen

• Medication to Suppress nerve stimulation

  • Phenytoin

• Supplements to decrease inflammation

  • Vitamin E

  • Vitamin B

Surgical correction may be successful for some cases of classical stringhalt. In this procedure a section of the tendon that runs over the hock and a portion of the muscle that it inserts into are removed. Surgical results range from no improvement in the horse’s condition to almost complete resolution of clinical signs. Unfortunately, there is no way to predict how an individual horse will respond to the surgery.

Recovery and Management of Stringhalt in Horses

Almost all cases of bilateral stringhalt will eventually make a full recovery when the horse is removed from the toxic pasture. However, progress is slow and can take up to 18 months depending on the severity. Recovery to full athletic performance is unpredictable and depends on the horse. Your equine veterinarian will help you to determine the recovery routine depending on your horse.

Recovery from classical stringhalt varies depending on the severity and underlying cause of the condition. Despite treatment, most cases will progressively get worse until they reach a point where they stabilize. This is because the initial inflammation and damage that occurred has subsided and now there are residual effects.

Some cases of classical stringhalt in horses may improve with time, but recovery may range from months to years, if at all. In cases that do not resolve, the horse owner will need to manage the condition long-term. Depending on the severity of the condition, long-term management will vary.

In mild cases, management may be no more than just being aware of your horse's condition and monitoring for any changes. In severe cases, a horse may need to be retired. Care should be taken to make sure that the horse's environment does not have tripping hazards or hindrances to them obtaining food and water on their own. Your veterinarian will help you establish a management routine.