wedge vertebra
Single wedge vertebra with curvature of the spine (left). Double "butterfly vertebra" (right).

Currently, a dissertation on the genetic elucidation of wedge vertebrae in the French Bulldog is underway at the Institute of Animal Breeding and Genetics of the University of Veterinary Medicine Foundation Hannover. For the further procedure it is very important to obtain as many blood samples as possible, also from other breeds in which wedge vertebrae occur.

PhD Thesis Objectives:

  • development of a genetic test that detects the genes responsible for wedge vertebrae.
  • of interest to all breeders of dog breeds in which wedge vertebrae may occur
  • necessary: EDTA blood samples including a completed submission form from animals of different breeds in which wedge vertebrae occur
  • different breeds should be included in order to find the genes responsible for wedge vertebrae by mapping breeds with different incidences of wedge vertebrae.
  • further procedure: the blood samples will be analyzed in the laboratory of the Institute for Animal Breeding and Genetics for the genes causing wedge  vertebrae and tests will be developed for these genes
  • all data are anonymized and not passed on to third parties

Wedge vertebrae - origin, occurrence and clinic

Introduction

  • dogs were bred in the past to reinforce certain positive characteristics and to select for certain body shapes
  • the occurrence of wedge vertebrae has been described for more than 100 years
  • mostly wedge vertebrae occur in small, brachycephalic breeds with corkscrew-shaped, shortened tail ("screw-tailed" breeds)
  • the tail itself consists of wedge vertebrae
  • breeding for such a tail shape also leads to an increased risk of wedge vertebrae in other parts of the spine


Origin of wedge vertebrae

  • the cartilage of the primordial vertebrae during embryogenesis occurs via 3 paired cartilage centers, which fuse at the end and then ossify (ossification centers)
  • the cartilaginous vertebra serves as a placeholder for the later bone during the development of the fetal skeleton
  • wedge vertebrae are caused by inadequate nutrition of the fetal cartilage, the altered blood supply leads to a deformation of the later bone
  • Wedge vertebrae often occur in chondrodystrophic breeds (chondrodystroph= disorder of cartilage formation)
  • wedge vertebrae can be present singly or in multiples

Shapes of wedge vertebrae

1. Simple/unilateral wedge vertebra

  • results from an asymmetrical development of the vertebral body halves in relation to each other
  • it is wedge-shaped
  • the narrower end can be directed upwards, downwards or to the side


2. Double/bilateral wedge vertebrae

  • it is caused by a lack of fusion of the ossification centers of the left and right halves of the vertebral body
  • it is butterfly-shaped (butterfly vertebra)


Affected breeds

Mainly chondrodystrophic breeds:      

  • French and English Bulldog
  •  Boston terrier
  •  Pug


However, there are also cases in:

  • Doberman, Pinscher
  • Westhighland White Terrier, Fox Terrier, Yorkshire Terrier
  • Beagle
  • Miniature spitz
  • Rottweiler
  • Pekinese
  • Mongrels
  • German Shepherd Dog
  • German Shorthair


Localization

  • mostly wedge vertebrae occur in the area of the thoracic spine
  • often in the area from the 5th to the 9th thoracic vertebrae


Possible symptoms

  • symptoms depend on localization and number of affected vertebrae
  • the animals are often symptom-free or the symptoms disappear after the end of vertebral growth (around the age of 9 months)
  • clinical problems result from curvature of the spine and pressure of vertebrae against the spinal cord up to spinal cord transection in the form of:
    • Movement coordination disorders, paralysis
    • Decreased reflexes and ability to stand as well as muscular atrophy of hind limbs
    • Pain of the affected spinal segments
    • kyphosis, scoliosis, lordosis
    • Incontinence of feces and urine


Heredity

  • wedge vertebrae are hereditary
  • the mode of inheritance in French Bulldogs and Pugs is still unclear
  • probably more than one gene locus is involved
  • in German Shorthair and German Shepherd there is an autosomal recessive mode of inheritance
  • in humans there is a familial clustering


Breeding strategies

Problems:

  • Limited gene pool, so that recessive defects also come to light


Solutions:

  • international gene banks with sperm from different populations
  • new breeding standards
  • animal identification and pedigree checking before mating
  • prior breeding testing by veterinary examination
  • cross between two breeds, continue with these dogs after backcrossing three to four times
  • develop markers to identify responsible genes
Simple wedge vertebrae
Simple wedge vertebrae in the thoracic spine (marked with arrows).
Double wedge vortex
Double wedge vortex