Low-Rider Dogs Are at Greater Genetic Risk for Type I IVDD—Now We Can Test for It

October 23, 2019

 Type I Intervertebral Disc Disease, or a slipped disc, is common in numerous dog breeds, and it’s now part of Embark’s health panel.

 

We’re pleased to announce that as of today, Embark’s genetic health screening includes the mutation for Type I Intervertebral Disc Disease (IVDD), often referred to as a slipped or herniated disc. This condition is common in “long and low” breeds like Dachshunds, Corgis, and Basset Hounds. Every dog tested with Embark, both past and future, will now receive results for this test in their health panel. Armed with that knowledge, owners can take steps to reduce the risk of an IVDD incident in their dogs.

What is IVDD?

Type I IVDD occurs when the soft center of the spinal disc—AKA the nucleus pulposus—is squeezed out into the spinal canal, compressing the spinal cord. IVDD is a degenerative condition that can cause back pain and limit mobility. Afflicted dogs may show a sudden onset of hind leg weakness, paw dragging, and/or back pain. Treatment ranges from conservative medical management and rest to surgery, in which case the extruded disc material and some parts of the vertebrae are removed. Physical therapy is also recommended to help your pup get back up to speed.

 

The Genetic Basis for Type I IVDD

In 2017, researchers at the University of California, Davis discovered a genetic mutation that increases the risk for a slipped disc in short-legged, long-bodied breeds, a skeletal conformation known as chondrodystrophy (CDDY). Note that another mutation that causes a similar conformation, called chondrodysplasia (CDPA), was discovered many years ago. However, the CDDY mutation has a bit more to it.

The research team started with Nova Scotia Duck Tolling Retrievers. They had observed that some Tollers had shorter legs than others and that these shorter-legged dogs were much more likely to develop Type I IVDD. When they identified a mutation predictive of CDDY phenotype, they also found that the dogs diagnosed Type I IVDD had more that 50x greater odds of having the mutation compared to dogs who were Type IVDD free (Odds Ratio = 51.23).

The study did not evaluate the relative risk in mixed breed dogs, but given that Type I IVDD is diagnosed regularly in mixed breeds, it’s likely that the mutation plays a role in at least some mixed breed cases. Although there’s more to be discovered about the risk factor for mixed breeds, knowing about this potential genetic risk gives you and your vet a chance to discuss preventative care and monitoring.

How We Test For IVDD

We’re always on the lookout for new genetic discoveries that can be incorporated into our testing panel and have actionable results for owners, breeders, and veterinarians. There are different ways we do this, and in the case of IVDD, it’s through a linkage test. DNA sequences that are close together on a chromosome tend to be inherited together, so we’re able to infer the presence or absence of a mutation of interest by examining the genetic variation surrounding it. Since linkage tests don’t directly look at a mutation of interest, they may not be perfectly predictive of your dog’s true genotype. However, by our most recent analyses, Embark’s linkage test is over 99% predictive of IVDD genotype.

What to Do if Your Dog Tests Positive for the IVDD Mutation

Keep in mind that a genetic risk is not a diagnosis. Just like in humans, the risk for a dog experiencing a herniated disc is affected by several factors, including other genes, diet, exercise, and lifestyle. While this mutation result may inform risk, it’s not a guarantee of disease, and there are lots of things you can do that may help your dog avoid a slipped disc altogether.

First on the list of preventative tips is to keep your dog physically fit and in good body condition. This is associated with reduced IVDD risk, at least in Dachshunds, one of the high-risk breeds for the condition. And if your pup is regularly jumping on and off of the sofa or bed, a set of doggy steps can help.

If your dog does experience a slipped disc, they’ll have a better chance for recovery the sooner they’re treated, so owners with at-risk dogs should be on the lookout for any signs of back pain or spinal cord compression. Take note if your dog is less willing to jump into bed at night, is reluctant to run during play, or has trouble posturing to poop or pee. Your dog’s walking cadence can also provide clues. Are they sliding or scuffing their paws to walk, instead of picking them up and setting them down? Are the nails on one paw getting more worn down than the others? If so, a trip to the vet may be in order.

And tell us about it, too! Like we said, not too much is known about how risk is impacted by being mixed breed. If your dog has been diagnosed with IVDD, please let us know by filling out your Medical History Assessment or emailing us at askthevets@embarkvet.com.

To learn more about our ongoing research efforts at Embark, see embarkvet.com/research.