If horses suddenly become difficult to ride, stumble more frequently or even fall, coordination disorders occurring as a result of changes in the spinal region are a possible cause. Malformations in the lower cervical spine in particular have the potential to trigger clinical manifestations, i.e., abnormalities that can be detected without further diagnostic aids. For this reason, ECVM (Equine Complex Vertebral Malformation) is currently being intensively discussed in equine circles.
The deformations of the vertebrae of the lower equine cervical spine occurring in the context of this condition primarily affect the sixth and seventh cervical vertebrae. The changes comprise the unilateral or bilateral absence of the bony process on the underside of the sixth cervical vertebra, which is partly accompanied by a structural transformation of the seventh cervical vertebra and the first rib.
Due to the increasingly frequent and comprehensive radiographic examinations of horses, more and more data on findings in the (cervical) spine are available. Classifying these findings with regard to causes, influencing factors and clinical relevance is often difficult. Both the veterinary profession and horse breeding wish to uncover the connection between the occurrence of ECVM and clinical symptoms as well as potential heritability. Scientifically sound findings are required in order to be able to make sustainable decisions on veterinary and breeding measures on a solid basis.
Classification of the condition
ECVM is by no means a new condition that appeared for the first time in the modern riding horse and sport horse. Rather, such structural changes in the lower equine cervical spine were described many decades ago and are documented by horse skeletons exhibited in museums and case reports on post-mortem findings. Such variations in the cervical spine are also and particularly documented for the Thoroughbred. Most published results refer to this breed.
Particularly in horses that are nowadays mostly used for sport, the structures of the lower cervical spine play a literal load-bearing role. They serve as an attachment point for ligaments and musculature of the forehand, which include important trunk and limb supports. However, the functional relationship between the skeletal-recognizable or radiographically displayable change and the clinical abnormality of the affected horse remains unclear at the present time.
Previous studies have not been able to establish a clear connection between structural changes of the lower cervical spine and the occurrence of symptoms recognizable without diagnostic aids. This contrasts with reports and practical experience that horses with problems in rideability and movement also exhibit radiographic findings in the sense of ECVM. This suggests that a certain degree of variation in the formation of the cervical vertebrae is normal and unproblematic, but in individual cases may also be of pathological significance. Determining this pathological significance, or ascertaining the criteria that constitute it, is considered an urgent subject of research that requires targeted and comprehensive investigation.
Although it is known that the described changes to the cervical spine are congenital, it remains unclear to what extent they are hereditary and how much variation, especially with regard to potential clinical relevance, results from environmental factors such as feeding of the broodmare during gestation, movement management of the foal, or later riding and training. Consequently, it is currently also unknown how many and which genes or gene variants significantly influence this trait. Veterinary medicine, horse breeding and research must work closely together to answer these pressing questions scientifically.
Clinical symptoms
The clinical presentation of ECVM is very comprehensive and ranges from being asymptomatic to spinal ataxia, i.e., disturbances of balance and movement coordination originating from the spine. Affected horses may present with mild to severe movement restrictions in the neck region and forehand. Affected horses are often noticeable due to increased stumbling up to falls or an unsteady gait. Due to the unphysiological use of the musculature and under certain circumstances compression of the cervical nerves at the transformed vertebrae, horses may show pain when moving the neck as well as in the musculature itself. In severe cases, atrophy, i.e., wasting of the neck musculature, occurs.
Research network
The International Association of Future Horse Breeding GmbH & Co KG (IAFH) is committed to increasing knowledge in horse breeding and supports research on practice-relevant topics. As part of the ECVM study launched in 2023 at the initiative of the IAFH, the question of the frequency of occurrence of lower cervical vertebra malformation in the warmblood horse is to be investigated first. Comprehensive data collection is planned to be carried out on a larger sample of warmbloods to enable meaningful analyses on the relationship between genetics, structural and clinical abnormality. The horses undergo a general clinical and neurological examination. Objective movement data, collected using sensor technology, are intended to further strengthen the database. To depict the structural condition of the cervical vertebrae, the lower cervical spine is radiographed, which requires high-performance X-ray technology and examiner experience. SNP genotypings are already routinely arranged by the participating eleven riding horse breeding associations for the parentage verification of all foals, so that individual genetic profiles are available. These can now help in the ECVM study to get to the bottom of the genetics causing the changes in the cervical vertebrae.
Since horse health is of high importance to the horse breeding associations, the ECVM study marks the launch of a large-scale and comprehensive research project to elucidate the backgrounds and connections of ECVM. The study is conducted jointly by scientists from the Research Institute for Farm Animal Biology (FBN) in Dummerstorf, the University of Veterinary Medicine Hannover, Foundation (TiHo), and the computing centre Vereinigte Informationssysteme Tierhaltung (vit). Experienced radiologists and specialist veterinarians for horses as well as scientists from the animal breeding institutes of the universities in Göttingen and Kiel are also available for professional consultation. The study is supported and financed by the IAFH.
About the IAFH
The International Association of Future Horse Breeding GmbH & Co KG (IAFH) was founded with the aim of unlocking the potential of genomics for horse breeding. Since an individual association would hardly ever have been in a position to accomplish the necessary foundational work alone, it was necessary to break new ground.
In association with partners from practice and in close cooperation with science, it was intended to succeed in reaching the critical mass of horses with genome-wide SNP data and trait information in order to ultimately be able to establish genomic-supported applications in the riding horse and sport horse. In addition, joint investments by practice in research and development work also mean opportunities for shaping things. The Verband der Züchter des Holsteiner Pferdes e.V. is involved in the IAFH as a shareholder.
Further information on the IAFH
Photo: IAFH
