Just What are Equine Shivers and How Are they Treated?


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Just What are Equine Shivers and How Are they Treated?

Morgan Murphy

Just What are Equine Shivers and How Are they Treated?

Shivers (or shivering) is thankfully, a fairly unusual condition, affecting primarily warmbloods and heavy draft breeds. It affects the hindlimbs of the horse, causing the horse to hold the leg excessively flexed and turned outward.

The hind legs of the horse are affected by shiver*

What is Shivers?

It is frequently the farrier who detects the presence of early-stage shivers. The horse maybe reluctant to lift the leg, be unable to hold up the affected leg or have trouble standing on three legs for any length of time. As a result, the farrier may have difficulty trimming or shoeing the affected limb.
When handling your horse, you may start to notice that the horse is reluctant to use the affected limb and may hesitate or refuse to have the leg picked up; for example, when picking out the hoof.
In later stages of shivers, you may notice that when the leg is lifted or when the horse is backed up, the horse will pull the leg high, rotating and holding it out for a few seconds before placing it back on the ground. The muscles in the thigh may tremble and the tail may arch and shake. The muscles in the face may also be affected, the horse will stretch the neck forward and the eyelids, lips and ears may flicker repeatedly. In some severe cases, the hind leg may be held rigidly behind the horse or, the horse may be seen to stand on his hind toes with heels elevated off the ground (“tip toes”).
Generally, the symptoms are seen at the walk or when the horse is turned on a tight circle. It is uncommon to see signs at the trot or canter unless the condition is extremely advanced.
Shivers appears to get worse when the horse is stressed, anxious or excited and during periods where he is not exercised.  

What Causes Shivers?
This is the million dollar question and as yet, we don't have an answer. One theory suggests that Shivers is caused by an underlying neuropathy or nerve problem. Although studies have been conducted analyzing nerve pathways from the brain's stem through the spine's length, (in both post-mortems and living Shiver sufferers,) they have been consistently proven inconclusive.

Another faction suggests there is an underlying muscle disease called PSSM (polysaccharide storage myopathy,) as both Shivers and PSSM have been observed in some equine patients. Unfortunately, no study has yet established a conclusive link.

Other researchers suggested the nerve damage is the result of an infection such as Strangles or Osteoarthritic lesions to the spine, but again, there is no evidence to support this theory.

It is clear that Shivers appears to have some hereditary component. It is far more common in draft breeds and warmbloods, as well as in male horses over 16hh. The age of the onset of clinical signs is typically between 2-4 years. There is some opinion that the horse species being bred to sizes of 16 hands and above is an inherent part of the issue with Shivers.

Treatment Options For Shivers in Horses.

Because the genuine cause is unknown, diagnosis is, of course, difficult. It is usually based on recognition of the symptoms by farriers, owners and veterinarians, combined with the systematic elimination of other disease diagnoses.

The prognosis for horses with Shivers is generally poor: many cases remain in a plateau, but the majority will worsen over time. Wasting of the muscles across the thighs and hindquarters may become increasingly apparent, with the horse's back-end eventually becoming weak and stiff. Many horses are willing to continue to attempt to work, but, this progressive disease often robs them of this ability. They may eventually have trouble simply traversing their fields. In some horses, the discomfort and inability to move associated with muscle cramping can actually become so severe that euthanasia is the only humane option available.

Because our understanding of this disease is still limited, treatment options are unreliable and no consistent results have been achieved with any therapy. Many veterinarians will prescribe non-steroidal anti-inflammatory drugs such as phenylbutazone in conjunction with muscle relaxants and anticonvulsive drugs but, even with these drugs, the horse may show no sign of improvement.

Allow a horse diagnosed with Shivers as much turnout time as possible. Calm, quiet surroundings and minimal drama can help reduce the number of episodes. However, a reduction in exercise can trigger symptoms, so, an exercise program should be continued as long as physically possible to limit progression of the condition. Horses kept on rest actually degenerate more quickly and experience more spasms than horses who are regularly turned out and exercised.

Currently, Shivers is a poorly understood condition. Research is currently underway at the University of Minnesota looking into a potential link between Shivers and Recurrent Laryngeal Neuropathy (or RLN, also known as “roaring:” A loud respiratory noise heard during hard work) We'll keep an eye on the University's progress and let you know what they've learned as soon as they publish their studies. If you know a horse or horse owner who's struggled with Shivers, let us know, here at Spalding Labs. Part of being part of our horse community is sharing your news and observations with others, both the good news and the "teaching moments."

 *Image courtesy of Dollar Photo Club


  • Really interesting Morgan, I had not heard of this condition before, I am really pleased to read your blogs to learn so much!

  • I have a 16 hand mule that was just diagnosed with shivers and I have another 15.2 hand mule with the same symptoms. If you have any more info on what will help with these symptoms please let me know. This is such a sad disease.