Degenerative Myelopathy (DM) and the French Bulldog
DM (degenerative myelopathy) is a disease that occurs at the other end of French Bulldog life.
This is a devastating condition that gradually whittles away the mobility and effectiveness of the entire hindquarter. Unfortunately it occurs well after the age of breeding, usually 8-9 years and older.
The disease affects the myelin sheaths of the spinal cord, affecting from mid thoracic area back, with the messages getting slower and slower to the hindquarters. The only good part of this disease is that it is not painful to the dog. The disease course runs some 12-18 months with affected dogs usually being euthanised due to inability to stand etc.
This disease has been found in many breeds, over 135 breeds at last count (and in mixed breeds). The DNA test has been available only over the last 4-6 years. This disease is inherited as a simple recessive condition but it is complicated by a late onset which can vary from as early as 8 years to very late, to the point the dog may die from other conditions, without exhibiting any obvious signs. It appears that there may be additional triggering factors that then cause the disease to manifest as the dog ages. There is considerable research ongoing in this area that may hopefully clarify the situation.
As a result, DNA affected dogs with DM are being called “at risk” rather than affected, as only 1 in 2-3 will physically become affected prior to their death.
The number of physically affected older dogs that are seen would be in the order of around 1-2% of older French Bulldogs. Many of these may be misdiagnosed as having disc or other spinal issues which are not uncommon in the Frenchie. Some dogs may be unlucky enough to be affected with several of these conditions concurrently.
The current carrier rate is estimated around the 8-10% level.
Breeding Advice and DM
There is a certain recent degree of concern in regards to this condition. This is totally unnecessary. The aim of any DNA test is to clearly sort out the various categories of normal, carrier and in this case “at risk” animals.
The whole point of having a test is that we can avoid breeding any more “at risk” dogs very easily. At risk and carrier dogs and bitches should ideally only go to normal partners, the absolute worst that can be produced is a carrier. Gradually over time the incidence of the gene can be lowered in the population.
Our aim is to reduce the incidence of severe disease in our breed, NOT to reduce the genetic variability (and viability) of our population. The more diseases we try to control, the slower our overall progress, we need to move carefully as any sudden contraction in the gene pool often results in other conditions coming out of the “woodwork” as a result of the reduced viability of the remaining population.
Whilst I do not believe that we need to do extensive testing of breeding stock at this stage, it would be worth testing heavily used stud dogs, or bitches which kennels are based on in order to give breeders more information when making breeding decisions. Where major animals within the kennel have subsequently developed DM in their old age, ideally test retained progeny and take care with selecting clear breeding partners.
The number of cases of DM and HC are under reported. Use of the Health Report can assist us in ensuring we are improving the overall health of the breed as well as giving us more accurate statistics.
SNIP tests—when DNA testing SNIP tests are now available that will test all known (and recognised) diseases in any breed. These will also test for parentage (where generational data exists). It is now cheaper to test this way than for individual disease testing. Current costing is around $60-65 for 1 disease and around $135 for 3-4 diseases plus parentage.
Dr Karen Hedberg BVSc
From the French Bulldog Club of NSW Inc Website
Diagram from the Orivet DNA Website.'