If you aren't familiar with dog DNA, you may want to start with this previous post for a general explanation as this post is a little more detailed and covers only one test, IVDD.
As we've described and explained in previous posts, we DNA test all of our dogs for genetic conditions. Until recently, we were able to proudly boast that the majority of our dogs were "completely clear" of all genetic defects tested by Embark. And then, Embark introduced a genetic screening for IVDD and the vast majority of our dogs (and all Cavalier King Charles Spaniels) suddenly had a blemish on their records. Since that time, we've had conversations with Embark, our vets and leading specialist to better understand why this happened and what it means.
For breeders, the goal in doing genetic health screenings is to reduce the instance of genetic illness within the breeding program, while also continuing to work on reducing inbreeding and other genetic issues that aren't identified by genetic testing (such as heart disease in the Cavalier). So what do you do when every dog in your program shows a predisposition towards a genetic condition? Well, you research and determine what to do. Here is what we've learned:
First, what is IVDD? IVDD is short for Intervertebral Disc Disease which refers to a condition such as a slipped or herniated disc. In simpler terms, it means a predisposition to having a back problem. IVDD occurs when the soft center of the spinal disc squeezes out in to the spinal cord, compressing it. IVDD can be degenerative condition that can cause back pain and limit mobility. Affected dogs may show a sudden onset of hind leg weakness, paw dragging, and/or back pain.
How does Embark test for IVDD?
IVDD is a linkage test. Because linkage tests don’t directly look at a variant of interest, they may not be predictive of your dog’s true genotype. Essentially, Embark is looking at DNA sequences that tend to be inherited together to infer the presence or absence of a genetic variant.
Why do the majority of Cavaliers have this variant?
This is where DNA starts to make sense. This linkage test is picking up the DNA for a certain body shape. Dogs with two copies of the IVDD variant typically appear to have shorter legs and a longer body. This is known as the "long and low" body shape. Other breeds where the vast majority of the dogs will carry this variant include Dachshunds, Basset Hounds and Corgis. So, the reason that almost all Cavaliers have the DNA variants is simply because the shorter legs and longer body predispose them to back problems. The test is new, but the news is not.
Now what do breeders do with this information?
Other genetic tests have allowed the responsible Cavalier breeder to strategically eradicate the predisposition of disease from their program. Good examples are the tests for Episodic Falling, Dry Eye / Curly Coat and DM. This test is different. The number of Cavaliers who do not carry the IVDD markers is very small. And, the reason some of them don't carry the markers is that their legs are too long and they don't meet the breed standard. And, if breeders only breed those dogs, we will effectively be changing the size, look and shape of the Cavalier. Imagine any of these breeds with long legs? The Dachshund as we know it would be gone.
Lastly, if we use IVDD variants to reduce our breeding pool, we will be causing problems much worse than a predisposition to IVDD as inbreeding would skyrocket! Unfortunately, this is one test that provides us with information (i.e. a long and low body shape is more likely to lead to back problems) but no solution other than to take precautions!
How can I prevent IVDD in my Cavalier?
There are many things you can do help your dog avoid a slipped disc. Here are our tips:
1) Most importantly, keep your dog physically fit and in a proper weight range to avoid unnecessary strain on the back. This is SO important for all Cavaliers due to heart issues as well.
2) Set up dog-friendly steps or ramps for your Cavalier to get on and off of furniture such as beds and sofas to reduce the impact of jumping on the back and neck.
3) Reduce strain on the spine and neck by walking your dog in a harness.
4) Wait until your dog is fully matured before spaying or neutering your pet. Early spay and neuter has been linked to many health issues - just one of which is increased spinal issues.
Just A Little Cavalier is always working to improve the Cavalier breed. We take our DNA and OFA testing very seriously and we work to pair dogs that will only produce the healthiest Cavalier's possible. Sometimes this might mean breeding a solid color (Black & Tan or Ruby Cavalier) with a Parti Colored (Blenheim or Tri-Colored) because they are the best genetic matches, even through we may get a splash of white on a solid puppy. Because of all the health problems that plague this breed, we put health before color choices. We put health before producing the perfect nose or coat for winning a ribbon at a show. We put health before profit. We put health before all else. Please make sure you work with a breeder who is doing the same.
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