Shivers, or shivering, in horses is a progressive neuromuscular condition characterized by an abnormal, jerky gait while backing up. [1]

Horses affected by Shivers exhibit muscle tremors in the pelvic limbs when forced to back up. Clinical signs typically appear in horses between two and five years old and gradually worsen. [2]

Shivers is more common in taller breeds, Warmbloods, and draft horses and affects geldings three times more frequently than mares. [2]

There is no effective long-term treatment for Shivers, but many affected horses can continue participating in certain disciplines for several years following diagnosis. As the condition progresses, horse owners may choose euthanasia to prevent injury or suffering.

Shivers in Horses

Equine Shivers is a chronic neuromuscular syndrome that results in a progressive loss of hindlimb muscle control during backward walking. [2]

The pelvic limbs may appear to shiver or tremble when attempting to back up. Shivers rarely affects forward movement until later in disease progression. [1]

The cause of Shivers is still not well understood, but research shows that affected horses have nerve damage in a specific area of the brain known as the cerebellum. Neurons in this part of the brain are involved in modulating learned muscle movements, including backing up and lifting the hindlegs. [2]

In 74% of cases, symptoms worsen over time. As the disease progresses, increased severity symptoms may lead to the premature retirement of the horse. [2]

If you think your horse is affected by Shivers or another neuromuscular condition, contact your veterinarian as soon as possible to schedule an examination and receive a diagnosis.

While there is no cure or treatment for this condition, early diagnosis and supportive care can make affected horses more comfortable and may help slow symptom progression.

Mad About Horses
Join Dr. Chris Mortensen, PhD on an exciting adventure into the story of the horse and learn how we can make the world a better place for all equines.
Apple Podcasts Spotify Youtube
Mad Barn - Equine Nutrition Consultants | Mad Barn Canada

Risk Factors

The prevalence of Shivers is unknown, but it is considered a rare disease. Tall horses (over 16.3 hands) have a higher risk than shorter equines, such as ponies. [2]

Draft horses and large breeds, including Warmbloods or Thoroughbreds and their crosses, are more commonly affected by Shivers than lighter horses. The condition has also been reported in other breeds, such as the Quarter Horse and Morgans. [3][4]

In one breed survey, 19% of Belgian horses were reported to have Shivers. [2]

Both male and female horses can be affected, but geldings are three times more likely to be diagnosed with Shivers than mares. It is not known why male horses have a higher risk.

There is no genetic testing for Shivers available.

Signs of Shivers in Horses

Shivers tends to develop gradually, but symptom onset can vary between individual horses. The majority of affected horses show signs of the disease by the age of seven, but some are symptomatic as young as one or two. [2][3][5]

Signs often become more apparent after the horse has been rested or stalled for a period of time or when walking in tight circles. [2] Following periods of stress or excitement, abnormal hindlimb movement may be exaggerated. [6]

In most cases, Shivers affects both hind limbs. [3][5]

Mild Clinical Signs

In mild cases, the hindlimbs of the horse may become tense and tremble when backed up. [6] Horses may be resistant to having their hindlimbs lifted, making it difficult to provide farrier care. [2]

Sudden jerking movements of the tail cause it to become erect and elevated. Some affected horses may display quivering ears and eyelids, as well as wobbling of the head when elevated. [6] Horses may also experience excessive sweating. [2]

In the early stages, signs of Shivers may be intermittent or occasional, making diagnosis difficult. [2]

Severe Clinical Signs

In severe cases, individual hind limbs may raise and extend from the body when the horse is backed or moved suddenly to the side. The limb may spasm in the air for a few seconds to several minutes. The thigh and flank muscles quiver while the leg is suspended.