CDPA/CDDY DNA Testing for IVDD in Dachshunds - update
In October 2017, University of California, Davis (UCD), researchers revealed the discovery of a genetic mutation across breeds that is responsible for chondrodystrophy (the skeletal disorder leading to shorter legs and abnormal intervertebral discs) in a study published in the Proceedings of the National Academy of Sciences. We reported this and their claim to have developed a DNA test for IVDD.
We worked with the Animal Health Trust on the genetics of IVDD and UCD generously agreed to screen a set of samples which we had collected for Dr. Cathryn Mellersh in the UK. These comprised UK dogs aged 4-7 who had suffered IVDD herniations and dogs over the age of 10 with no clinical history of IVDD symptoms. 144 samples were sent, covering Smooth, Long and Wire coats in both Standard and Miniature sizes.
These samples were all genotyped for both FGF4 retrogenes (CFA12 and CFA18) and unfortunately all samples were homozygous for both loci. We had hoped that the Wirehaired dogs might be variable at least (based on experience from other genetic studies), but that wasn’t the case.
So this means, sadly, that neither of these loci can be selected against to reduce the prevalence of IVDD, in UK Dachshunds at least.
These data also indicate that all the dogs we tested are homozygous for both of these risk factors. The fact that not all of these dogs had developed IVDD means either (i) environmental factors account for the ‘missing risk’, or (ii) that there are additional genetic risk factors that have yet to be identified. Or a mixture of (i) and (ii).
These findings reinforce those of our Danish colleagues who genotyped a similar sized sample of dogs that had (a) low calcification screening scores and (b) high scores. They found very few dogs without the (CDDY) mutation on CFA12.
New research projects are underway in the Nordic countries where they are genotyping many more Dachshunds to identify dogs that either carry only 1 copy of the CDDY mutation, or dogs that carry no copies (i.e. homozygous for the wildtype). Several interim reports have been shared that show the numbers of dogs with each genotype.
In the UK, we are in the early stages of a research project at Cambridge University to look for other genetic mutations that may be associated with IVDD. We will also be genotyping for CDDY and comparing these results with X-ray screening scores.
At the moment, our advice remains that the CDDY mutation is interesting to be aware of and to test for, but its value as part of a strategy for reducing IVDD risk needs more data.
Breeding schemes for intervertebral disc disease in dachshunds: Is disc calcification score preferable to genotyping of the FGF4 retrogene insertion on CFA12? Conclusions from this study: Our results show that the FGF4 retrogene insertion on CFA12 is not a valid risk indicator on its own. Relying on the DNA test will have an irreversible effect on the Dachshund breed excluding almost all dogs from breeding. Thus, using calcification status remains the most reliable breeding scheme for disc herniation in Dachshunds. The Kennel Club and DAchshund Health UK are both currently offering £100 subsidies on IVDD X-ray screening.
The CDPA/CDDY gene test is available from these laboratories (and others):
UC Davis VGL (USA) https://vgl.ucdavis.edu/test/cddy-cdpa
Canine Genetic Testing UK https://www.cagt.co.uk/product/chondrodystrophy-and-chondrodysplasia/
Wisdom Panel UK https://www.wisdompanel.com/en-gb/blog/ivdd-risk-variant
Genomia CZ https://www.genomia.cz/en/test/ivdd/
Read more about IVDD research on our website.
If you would like to make a donation to support our research, you can do so here.
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