American Chesapeake Club

What is Degenerative Myelopathy? Degenerative Myelopathy is a neurodegenerative disease with a relatively fast progression. Dogs initially lose function of their rear legs and can become unable to walk within 6 months to a year after presentation of symptoms. Dogs can also experience fecal and urinary incontinence. Paralysis can progress forward to affect forelegs. Age of onset is 7+ years of age. There is no treatment for Degenerative Myelopathy. Affected Chesapeakes require substantial support from their caretakers and ultimately owners must make the difficult decision to euthanize.

Is it inherited? Yes

How is it inherited? The mode of inheritance is autosomal recessive with incomplete penetrance. Dogs with two copies of the causative gene are considered to be “at risk” for the disease. Dogs that inherit one copy of the gene from one parent are known as “carriers.” Dogs that did not inherit any copies of the causative gene for DM are identified as “clear” or “normal.”

What is “incomplete penetrance” and how does it make the inheritance of DM different from other genetic diseases such as PRA or EIC? Geneticists use the term “incomplete penetrance” to describe a genotype that may or may not express itself. What this means is that a Chesapeake that inherits two copies of the gene associated with DM has a chance of not developing the disease. That is why they are identified as “At Risk.” Research is ongoing to help us learn what may cause or trigger the onset of this disease. In recent years, we have learned that there have been a handful of documented cases in which Chesapeake DM carriers (one copy of the gene) showed symptoms and were later confirmed to have DM. Guidance from researchers tell us that it is “far less likely” that carriers will present with DM.

Can it be prevented? In 2008, a genetic test for DM became publicly available and this was a game-changer for Chesapeake breeders and owners everywhere. With a simple cheek swab available from most canine genetic laboratories, breeders now have a tool that allows them to screen for the gene that produces DM and subsequently use the results to make sound breeding decisions aimed at preventing resulting puppies from suffering from this disease. Prior to 2008, breeders did not have any means for knowing if a young, breeding-age dog might one day develop Degenerative Myelopathy itself or be able to pass DM onto their offspring. Because it is a late-onset disease, most dogs were retired from breeding before they might begin to show symptoms of the disease. By that time, their own offspring may also have produced puppies and several generations of dogs capable of having and/or producing DM could be on the ground. Thanks to the development of the genetic test for DM, we’ve turned a corner in our ability to breed healthier dogs. The American Chesapeake Club recommends that all breeding animals be screened for Degenerative Myelopathy prior to breeding.