It is characterized by muscle tremors, difficulty holding up the hind limbs, and an unusual gait when the horse is asked to move backwards.
[5] While shivers is classically associated with the hind end, horses may also occasionally show spasmodic contraction of the muscles of the head and neck, including twitching of the ears and lips, and rapid blinking.
[2] Despite histologic changes in the cerebellum, horses with shivers do not show clinical signs typical of cerebellar disease (ataxia, intention tremors).
[2] In mild cases, shivers may present only when the horse is asked to move backwards, usually seen as trembling in the muscles of the hind limbs and sudden, upward jerks of the tail.
More severely affected horses will produce a backward gait where the hind legs are lifted abnormally high, held abducted for a period of time at the height of flexion, before the limb is slowly extended and the foot is placed on the ground.
[2] The horse may become unable to hold its feet up for trimming by a farrier, although use of alpha-2 agonist drugs, such as xylazine or detomidine, has proven helpful in reducing signs during farriery visits.