What is CDDY & Type I IVDD?

Intervertebral Disc Disease (Type I)

Type I Intervertebral Disc Disease (IVDD) is a back/spine issue that refers to a health condition affecting the discs that act as cushions between vertebrae. With Type I IVDD, affected dogs can have a disc event where it ruptures or herniates towards the spinal cord. This pressure on the spinal cord causes neurologic signs which can range from a wobbly gait to impairment of movement. Chondrodystrophy (CDDY) refers to the relative proportion between a dog’s legs and body, wherein the legs are shorter and the body longer. There are multiple different variants that can cause a markedly chondrodystrophic appearance as observed in Dachshunds and Corgis. However, this particular variant is the only one known to also increase the risk for IVDD.

Please note that this variant is extremely common in many small and chondrodystrophic dog breeds. In these breeds, this variant may not be the strongest predictor of IVDD risk compared to other genetic or environmental factors.

A dog with one copy of this variant may have slightly shorter legs in relation to body size. A dog with two copies of this mutation will have much shorter legs and a longer body. A dog with one or two copies of this variant has an increased risk of developing IVDD. Research has shown that one or two copies of this variant create a 46-fold increase in risk for an IVDD event and a 5-15 fold increase in risk for disc surgery.

A dog with one or two copies of this variant has an increased risk of developing IVDD. Research has shown that one or two copies of this variant create a 46-fold increase in risk for an IVDD event and a 5-15 fold increase in risk for disc surgery.

So what is CDDY, IVDD, or CDPA, and how do they relate to your Goldendoodle and Bernedoodle? Here’s a glossary of each of these:

CDDY: This stands for Chondrodystrophy, which is a mutation within the dog’s chromosomes. This is a semi-dominant trait that can contribute to shortened legs and an increased risk of IVDD in susceptible breeds. It was discovered only a few years ago, and it’s more common in some breeds than others. For instance, according to a particular study, the CDDY allele occurred in all of the Cavalier King Charles Spaniels tested, and 75% of the miniature poodles tested. However, it only occurred in less than 6% of the standard poodles tested. So, it could be fair to say that it CDDY appears in the smaller-sized Goldendoodles, Bernedoodles, and especially Cavapoos, than the standard sizes.
IVDD: This stands for Hansen’s Type I Inter-Vertebral Disc Disease. It’s when the discs between vertebrae in a dog like a Goldendoodle begin to calcify and harden much earlier than usual in life. This then causes the Bernedoodle’s discs to prematurely break down. As the discs break down, they can herniate much easier, along with causing a significant amount of neurological pain and discomfort in your Goldendoodle or Bernedoodle. As we previously said, CDDY mutations increase the risk for IVDD.
CDPA: This acronym is short for Chondrodysplasia. It’s recognized by a particular protein (FGF4) in one of the dog’s chromosomes. through genetic testing This is a muscular-skeletal trait, when the cartilage growth plates in the Goldendoodle or Bernedoodle’s legs do not develop properly. This will lead to the Goldendoodle having a normal sized torso, but their legs will be shorter. This trait has become normal in particular breeds such as Daschunds. Bernedoodles with two copies of the CDPA allele will typically have shorter legs than Bernedoodles with only one copy of the CDPA.

Stokeshire’s approach to CDDY/IVDD is somewhat different. It’s also informed by the perspective of GANA (Goldendoodle Association of North America). Here are some of the variables behind it.

First, we have yet to hear of a case where a Goldendoodle - or a Bernedoodle - has suffered IVDD as a result of CDDY. GANA has had some extensive discussion surrounding this, and none of the breeders had an example of an IVDD case in all of our vast experience in breeding Goldendoodles, especially mini Goldendoodles and petite Goldendoodles. So, it does initially appear like Goldendoodles are not prone to experience IVDD as a result of CDDY.

Second, most miniature poodles at least carry CDDY. As we previously mentioned, some estimates are around 75%. So, if Goldendoodle and Bernedoodle breeders try to only use breeding poodles and doodles that are clear of CDDY, then it will create a genetic bottleneck. This bottleneck can cause other unknown genetic issues to surface in the Goldendoodle and Bernedoodle populations.

So there is a tension with CDDY/IVDD in Goldendoodles and Bernedoodles. It doesn’t seem to be an issue for either of these hybrid breeds at this point; but it could just take time. However, creating a genetic bottle neck can lead to other issues that we don’t currently know at this time.

Gene names

FGF4 - chr12 ‐ chr12

Inheritance type

dominant

Spinal problems

Intervertebral disc disease (IVDD ) is a common condition in Poodles. The disease is caused when the jelly-like cushion between one or more vertebrae slips or ruptures, causing the disc to press on the spinal cord. If your dog is suddenly unable or unwilling to jump up, go up stairs, is reluctant to move around, has a hunched back, cries out, or refuses to eat or go potty, he is likely in severe pain. He may even drag his back feet or be suddenly paralyzed and unable to get up or use his back legs. If you see symptoms, don’t wait. Call us or an emergency clinic immediately! For less severe cases, rest and medication may resolve the problem. In many cases involving paralysis, we’ll recommend surgical removal of the ruptured discs (within 24 hours of the onset of symptoms to get the best results). As with so many other diseases, weight control helps to prevent this problem. You should also use ramps or steps from puppyhood on so that your dog doesn’t spend a lifetime stressing his back by jumping on and off of the furniture.

Chondrodystrophy, characterized by short limbs and intervertebral disc disease (IVDD), is a common phenotype in many of the most popular dog breeds, including the dachshund, beagle, and French bulldog. A report discovered that a FGF4 retrogene insertion on chromosome 12, the second FGF4 retrogene reported in the dog, as being responsible for chondrodystrophy and IVDD. Identification of the causative mutation for IVDD will impact an incredibly large proportion of the dog population and provides a model for IVDD in humans, as FGF-associated mutations are responsible for IVDD and short stature in human achondroplasia. This is a report of a second retrogene copy of the same parental gene, each causing complementary disease phenotypes in a mammalian species.

With respect to IVDD, the inheritance follows a dominant mode, meaning that 1 copy of the FGF4-12 mutation is sufficient to cause disc degeneration and predispose dogs to disc herniation.

The CDDY mutation is a risk allele, not a causative allele. That means it increases risk, but it is NOT shown to cause IVDD.

In general, the mutation causes a 5-15% greater risk of IVDD, depending on breed. Based on what we know of over a decade of records from GANA breeders, there is a very, very small incidence of IVDD in our breed and we are well on the lower end of this risk range.

The lack of IVDD in our breed is likely because the conformation of our dogs does NOT lend itself to luxation in the spine (this is per Dr. Robert Grahn at UC Davis).

A recommended course of action

About half of Goldendoodles have this mutation, although we have very, very few reports of actual disc disease in Goldendoodles.

There is clear consensus from the experts that removing the mutation from the gene pool too quickly and without careful planning will be very harmful for the breed and the gene pool. In fact, we have been told it would be better for the breed for us to NOT remove the gene than to remove it hastily or without careful planning.

The advice from the experts we have consulted has consistently been:

We should remove it not out of necessity but out of an abundance of caution, but we should not remove it at the expense of the genetic health of our breed.
It took a long time to get the gene dispersed into the gene pool and to remove it safely we should take a long time to breed it out.
Our goal should be to remove this from the gene pool over 5-10 years.
To remove it safely without damaging the gene pool the advice we received from the experts we consulted is to only use it as a “tie breaker” between two otherwise well-qualified breeding dogs and to NOT remove dogs from our programs simply because of CDDY status.

At Stokeshire, we plan to follow these recommendations in our program. We believe that by breeding this out too quickly we could inadvertently be causing more harm than good that could be far worse than the CDDY mutation, therefore we must do this with care and discussion.

IVDD Prevention

The advice we have received from UC Davis to reduce risk is:

Keep your dog in good shape.
Keep them fit and active.
Keep them at a healthy weight.
Avoid high-impact activities.

Degenerative Myelopathy (DM) vs. Intervertebral Disc Disease (IVDD)

IVDD and DM are genetic conditions, meaning that both conditions can be inherited and passed on to future generations if breeders aren't careful. Dogs with Degenerative Myelopathy and IVDD can experience mobility loss and loss of strength in their legs. Physical therapy can benefit dogs with either condition. A dog’s IVDD treatment depends on where in the spine the herniated and how bad of a rupture occurred. Crate rest is a standard method used to treat IVDD in dogs. There is no cure for Degenerative Myelopathy. All dogs with degenerative myelopathy will become paralyzed. The paralysis moves up the spine to impact the front legs and can progress to a point that it impacts a dog’s ability to breathe.

Learn more

References

Brown, E.A., Dickinson, P.J., Mansour, T., Sturges, B.K., Aguilar, M., Young, A.E., Korff, C., Lind, J., Ettinger, C.L., Varon, S., Pollard, R., Brown, C.T., Raudsepp, T., & Bannasch, D.L. (2017). FGF4 retrogene on CFA12 is responsible for chondrodystrophy and intervertebral disc disease in dogs. Proceedings of the National Academy of Sciences of the United States of America, 114(43), 11476-11481. doi: 10.1073/pnas.1709082114

Batcher, K., Dickinson, P., Giuffrida, M., Sturges, B., Vernau, K., Knipe, M., Rasouliha, S.H., Drögemüller, C., Leeb, T., Maciejczyk, K., Jenkins, C.A., Mellersh, C., & Bannasch, D. (2019). Phenotypic Effects of FGF4 Retrogenes on Intervertebral Disc Disease in Dogs. Genes, 10 435. doi: 10.3390/genes.10060435 Embark.com

Source: EmbarkVet