Epidemiology of shivering (shivers) in horses.
Authors: Draper A C E, Bender J B, Firshman A M, Baird J D, Reed S, Mayhew I G, Valberg S J
Journal: Equine veterinary journal
Summary
# Shivering in Horses: An Epidemiological Overview Shivering is a poorly characterised movement disorder in horses, characterised by difficulty lifting the hind limbs and abnormal hyperflexion or hyperextension during backward walking, despite apparently normal forward locomotion. A web-based international survey identified 27 confirmed cases (via video analysis) and 67 suspected cases, revealing that the condition typically emerges before age 5 years and progresses in approximately three-quarters of affected horses, with owners reporting concurrent muscle twitching (85%), atrophy (44%), reduced strength and exercise intolerance (33% each). Shivering showed a marked predisposition for taller horses (mean height ~173 cm versus ~163 cm in controls) and displayed a significantly higher male predominance (3.2:1 ratio) compared to control populations. Notably, draught breeds were overrepresented amongst confirmed cases, though the study identified no specific triggering factors or effective treatments in owner reports. For equine practitioners, this epidemiological characterisation provides valuable diagnostic criteria and highlights the importance of recognising early clinical signs in young, tall male horses; however, the lack of identified aetiological or management factors underscores the need for further investigation into underlying pathophysiology.
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Practical Takeaways
- •Shivering is a chronic progressive disorder—owners should be counseled that signs typically worsen over time and there are currently no proven treatments
- •Watch for shivering as a differential in tall, young male horses presenting with difficulty lifting hindlimbs and abnormal backward walking; confirm diagnosis via video documentation of hyperflexion/hyperextension patterns
- •Monitor affected horses for secondary complications including progressive muscle atrophy and exercise intolerance, as management strategies are currently supportive only
Key Findings
- •27 confirmed shivering cases showed onset typically before 5 years of age with 74% progression over time
- •Affected horses were significantly taller (mean ~173 cm) with male:female ratio of 3.2:1 compared to controls at 1.7:1
- •Associated clinical signs included muscle twitching (85%), muscle atrophy (44%), reduced strength (33%) and exercise intolerance (33%)
- •No potential triggering factors or effective treatments were identified in owner reports