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CDP position on CDDY/IVDD: A common mutation with implications for dog welfare

Recently, the Functional Dog Collaborative released an episode of the Functional Breeding Podcast in which FDC founder Jessica Hekman DVM, PhD interviewed UC Davis Professor Danika Bannasch DVM, PhD about her work on the CDDY mutation. If you haven’t listened yet, and you are a breeder or someone interested in functional breeding, we encourage you to do so now. There is a link at the bottom of this post. As a result of the recent podcast, CDDY/IVDD has been a hot topic among the breeders of CDP and others the last few months.

Chondrodystrophy/ Intervertebral Disc Disease (CDDY/IVDD) is an inherited disease of dogs that causes leg shortening to varying degrees, along with premature degeneration and calcification of the cartilage discs that connect the vertebrae and function as shock absorbers for the spine. In some cases, these degenerative changes result in herniation of one or more discs into the spinal cord, causing  inflammation, pain, and sometimes paralysis. The disease is associated with a genetic mutation in the FGF4 gene on canine chromosome 12 and is inherited in a dominant manner meaning only one copy is needed to create the disease.  There is variation in how much individual dogs are affected by the disease, and the likelihood of disc herniation may be breed or mix dependent. It is unclear exactly which factors increase the risk of disc herniation in dogs with the mutation, and how much the function of dogs without herniation is affected by calcification of discs. However, it is clear from available evidence that virtually all dogs with at least one copy of the mutation will have disc changes that have the potential to cause pain and affect quality of life. 

Many breeders, until recently, were unaware of the risk of pain in all  dogs with this mutation. Whether and how many dogs with the mutation actually have pain is controversial and the existing evidence is insufficient. It has been conventional wisdom for some time that unless a dog experienced a disc herniation, they were not affected by this disease. In the FDC podcast, Dr Bannasch explained her research findings about early degenerative changes in virtually all dogs with the mutation, and her concerns about pain being potentially overlooked by breeders and owners of these dogs.

Understandably, many breeders with affected dogs are deeply concerned about how to proceed, and breeders without affected dogs are wondering if they should avoid adding this mutation to their lines. 

The prevalence of the CDDY mutation in many breeds is overwhelming. In some breeds, including many small and medium breeds well suited to companion dog breeding, virtually all dogs carry one or two copies. Eliminating all of these dogs from the canine gene pool immediately would not be possible or helpful. If every CDDY/IVDD dog was eliminated from breeding immediately, a significant portion of existing canine genetic diversity would be lost, and many wonderful pet dog qualities, like those seen in Cavalier King Charles Spaniels, could be lost forever. 

Many apparently unaffected dogs exist with CDDY/IVDD. There are  actively competing sports dogs and working dogs with the mutation who do not display any evidence of disease. Owners report that many affected dogs are functional and mobile into old age with no evidence of pain. We believe this is true. We also believe that  a mutation known to be deleterious with no known functional benefit should be bred away from over time, even if its effects on any given individual dogs are not obvious or are non existent. The risk of pain and herniation outweighs the importance of perpetuating a mutation with no known benefit.

The Companion Dog Project supports the following strategies for the breeding of dogs with the CDDY/IVDD mutation when done as part of a defined strategy to remove the mutation over time, with full disclosure to potential  puppy seekers and owners, as defined below. 

Dogs bred in a manner consistent with these guidelines are eligible for registration in the Companion Dog Registry.

  1. All breeding dogs should be tested for CDDY/IVDD prior to breeding

  2. Breedings  that produce affected puppies should be part of a defined strategy to eliminate CDDY/IVDD, with the goal of producing breeding prospects, not simply for the production of pets

  3. Until further evidence is available about the prevalence of pain in CDDY affected dogs is available, litters in which every puppy is expected to be homozygous for CDDY will not be eligible for CDR registration

  4. Puppy buyers should be made aware of the risk of CDDY/IVDD affected puppies prior to placing deposits

  5. All puppies in affected litters should be tested prior to placement, and status should be considered in placement decisions

  6. Puppy buyers should be provided with educational materials outlining their individual puppies status, and when applicable, strategies for preventing injuries, and signs of pain to assess for 

  7. Puppy owners should be encouraged to share educational information with their veterinarian

It is the mission of the Companion Dog Project to set the standard for dogs bred to be family pets. We believe that by following these strategies responsible breeders can preserve the wonderful qualities we treasure in so many CDDY/IVDD affected dogs while improving the health of their future progeny, and setting an example for others about how to improve canine welfare through ethical breeding.  

Here is a link to the Functional Breeding Podcast about CDDY:

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