An Investigation into the Genetics of ‘Wobbler Disease’ in Thoroughbred Horses in Britain

Abstract

SUMMARY Sixty‐seven TB horses in Britain suffering from clinical wobbler disease were divided into 5 groups, based on the presence or absence of pathological lesions and their nature. These groups were compared genetically with a control group of 67 TBs known not to exhibit signs of wobbling. Though analysed for both simple and complex modes of inheritance no evidence of a genetic basis was found in any group. The high breed incidence in TBs may be real or apparent. Considerably more male than female wobblers are reported. Other forms of possibly inherited ataxia in equidae are reviewed and reference is made to pathologically comparable conditions occurring in man and in the large breeds of dogs. RÉSUMÉ 67 chevaux de Pur Sang montrant les signes cliniques du Mal de Chien furent divisés en 5 groupes en fonction de la présence ou de l'absence de lésions pathologiques et compte tenu de la nature de ces lésions. Ces groupes furent comparés du point de vue génétique avec un groupe de référence de 67 Pur Sang connus comme n'ayant jamais montrés les signes cliniques du Mal de Chien. Aucune évidence d'un support héréditaire de la maladie ne fut trouvé dans aucun des groupes qu'il s'agisse de transmission directe ou indirecte. La fréquence élevée de cette affection chez le Pur Sang n'est peut être qu'une apparence. On constate que les mâles sont plus souvent atteints que les femelles. On passe en revue les autres formes d'ataxie héréditaire chez le Cheval en les comparant à des phénomènes analogues connus pour se produire chez l'Homme et chez les chiens de grande taille. ZUSAMMENFASSUNG 67 Vollblüter, klinisch als “Wobbler” (spinale Ataxie) beurteilt, wurden in 5 Gruppen eingeteilt, je nach dem Vorhandensein oder dem Fehlen von Laesionen und deren Natur. Diese Gruppen wurden genetisch verglichen mit einer Kontrollgruppe von 67 Vollblütern, die keine Anzeichen einer spinalen Ataxie aufwiesen. Trotz einer Analyse einfacher und komplexer Vererbungsmechanismen konnten in keiner Gruppe Anhaltspunkte für eine genetische Grundlage gewonnen werden. Die hohe Rassenfrequenz bei Vollblütern mag real oder nur scheinbar sein. Es werden erheblich häufiger männliche Wobbier gemeldet als weibliche. Andere, möglicherweise hereditäre Ataxien beim Pferd werden besprochen und es wird hingewiesen auf pathologisch vergleichbare Zustände beim Mensch und grossen Hunderassen.

Examination of Frozen Cross Sections of Cervical Spinal Intersegments in Nine Horses with Cervical Vertebral Malformation: Lesions Associated with Spinal Cord Compression

“…In both cases, there was joint capsule and ligamenturn flavum thickening and osteophyte for-mation, indicating coexisting degenerative joint disease. In the 2 horses in this study and 1 horse in a previous study, 8 all 3 lesions were located at C [6][7] . Prevalence for synovial cyst formation at this site remains unclear at this time.…”

“…19,26 Some authors have suggested that CVM has a genetic predisposition in faster growing "performance" animals, 19 but others have refuted this theory. 7,9,22,34 These findings may be biased by economics, management, and the intended use of these horses and/or an over-representation of these breeds at referral hospitals capable of performing advanced diagnostic and surgical treatments.…”

“…1. Vertebral interspaces C 4-5 , C [5][6] , and C [6][7] were affected in 7 horses. Subluxation or malalignment of cervical vertebral bodies was noted in horse nos.…”

“…Prevalence for synovial cyst formation at this site remains unclear at this time. Frozen cross sections of the control horses demonstrated no variation in synovial morphology at C [6][7] .…”

“…Five of the 6 horses with narrowing of the vertebral canal were affected at a single site. Three horses were affected at C [5][6] , 2 horses at C [6][7] , and 1 each at C 3-4 and C 2-3 . Myelograms demonstrated multiple sites of spinal cord compression in all 3 horses (nos.…”