Comparative Neurology Program

Degenerative Encephalopathy with Sleep Disorder and Caudate Necrosis in Nova Scotia Duck Tolling Retrievers

DNA test now available

Researchers at the University of Missouri, College of Veterinary Medicine are pleased to announce that we have identified a genetic mutation that is highly associated with Degenerative Encephalopathy in NSDTRs. A DNA test for this mutation will permit the detection of dogs that have inherited two copies of the mutation and are at risk for developing the disease, and dogs that have inherited one copy of the mutation and have the potential of producing puppies that will develop the disease. See below for information about ordering a test. DE does not appear to be common in the breed, but further research will be needed to determine the full extent of the problem.

From the University of Missouri research team, THANK YOU to all the breeders, pet owners and veterinarians who contributed to this effort. We could not have done this work without your help!

What is Degenerative Encephalopathy?

This brain disease is called degenerative encephalopathy with sleep disorder and caudate necrosis or just Degenerative Encephalopathy for short.

The term encephalopathy comes from the Greek words for brain (encephalo-) and disease (-pathy) so it simply means a disease of the brain. NSDTR with the disease show progressive neurologic signs. They can be more anxious than normal at a young age, but learn basic obedience. With age, they become even more anxious and have difficulty concentrating and learning complex tasks. Coordination problems appear around 4-6 months of age. Often these are first noticed when swimming as the dog swims more upright in the water than normal. These signs progress to difficulty jumping, a “choppy” gait and falls when making turns by 12-18 months of age. Affected dogs can be hypervigilant, bark at inanimate objects, and be aggressive towards other dogs and sometimes people.

Another characteristic of the disease is a sleep disorder. The dreaming phase of sleep is called "rapid eye movement" or REM sleep because people and dogs move their eyes during their dreams. A normal dog will also make small, twitching movements of the paws or occassionally bark softly during this phase of sleep. In dogs with Degenerative Encephalopathy, the movements are exaggerated as if they are acting out their dreams. They also appear to sleep very deeply and are difficult to awaken.

An MRI scan allows the veterinarian to get a detailed view of the brain in their patients. Dogs with Degenerative Encephalopathy show a characteristic change in the brain on MRI scans which can help confirm the diagnosis of Degenerative Encephalopathy. Bright white spots appear in the area of the brain called the caudate nucleus which indicates necrosis (degeneration) of that area of the brain.

What else can look like Degenerative Encephalopathy?

There are other, much more common diseases that can cause similar symptoms. Metabolic diseases such as liver disease or low blood sugar could cause weakness and personality changes. Infections of the brain, such as canine distemper, can cause inflammation and similar symptoms. Injuries to the spine could cause weakness and loss of coordination. Consult your veterinarian to determine if any of these potentially treatable diseases could be the cause. If necessary, they can refer you to a Veterinary Neurologist board certified by the ACVIM who can help them make the diagnosis.

Since identifying a mutation associated with DE, we have recognized that there are dogs showing some of the symptoms of DE but do not have the mutations. These dogs that are clear of the mutation do not show the sleep disorder or caudate necrosis, but do show loss of coordination and behavior changes. Further research will be needed to determine what is causing the symptoms in these dogs.



One of the earliest symptoms of dogs with Degenerative Encephalopathy is difficulties swimming. They swim more upright in the water than normal.


Affected dogs sleep very soundly and make excessive, sometimes violent movements during the dreaming phase of sleep.


An MRI of a dog with Degenerative Encephalopathy can show bright white spots in an area of the brain called the caudate.

Is this a hereditary disease?

DE is an autosomal recessive hereditary disease. In a recessive disease, both parents of an affected pup will not show any signs of the disease. All animals have two copies of each gene, one that is inherited from the mother and one inherited from the father. A dog that has one normal gene and one bad (mutated) copy of a gene associated with a disease is a carrier of the trait. They show no symptoms because the one good gene is enough for their brain to function normally, but they will pass that bad gene on to about half of their offspring. If a carrier dog is bred to another carrier, then some of the pups (25% on average) may get a bad gene from each parent. Without one good gene to carry the day, the brain cannot function normally and the unlucky pup has the disease.

All the dogs with DE were born to normal parents and both sexes are equally affected. Several dogs have undergone extensive neurologic evaluations including MRI, spinal fluid analysis, tests for metabolic disease and post-mortem examination of the brain. No evidence of any other cause such as infection, trauma, brain tumors, toxicity or metabolic disease has been found in any of the dogs with DE.

Is there a DNA test for Degenerative Encephalopathy?

Yes, researchers at the University of Missouri have identified a genetic mutation that is highly associated with degenerative encephalopathy with sleep disorder and caudate necrosis. The brain function that would be affected by this mutation is disrupted in similar neurodegenerative diseases in people. Dogs that have two copies of the mutation (homozygous) are at risk for developing DE. In some hereditary diseases, every dog that is at risk develops the disease. Other hereditary diseases show what is called variable penetrance. In diseases with variable penetrance, not every dog that is homozygous for the mutation develops disease. Further research is needed to determine whether this occurs with DE, but thus far, all the dogs with 2 mutated copies of the gene have shown signs of DE.

The DNA test can also identify carriers of the mutation. Continuing to use carriers for breeding wisely will maintain genetic diversity in the breed and thereby preserve desirable traits in that line. To prevent producing an affected pup, a carrier of the mutation should always be bred to a dog that has tested clear of the mutation by the DNA test. Approximately 50% of the offspring of that breeding will be carriers, so the offspring should then be tested for the mutation. Whether the pups are also carriers should then be one consideration when deciding which dogs will be kept as future breeding stock.

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The Canine Genetic Diseases Network is a group of researchers dedicated to eliminating genetic disease in dogs

What research is going on to help us better understand Degenerative Encephalopathy?

The DNA test will allow identification of dogs at risk for developing DE and carriers of the mutation, but the situation in this disease may be more complex. There are reports of dogs showing behavior changes and coordination problems, but not the sleep disorder and necrosis of the caudate nucleus that are the hallmarks of DE. These dogs do not have the mutation associated with DE. Also one of the dogs with DE who had a post-mortem performed had additional changes in the brain that were not seen in other dogs with DE. This raises the question of whether there may be more than one brain disease in the breed. The DNA test will identify dogs with signs related to the mutation that has been identified. Those with signs of neurologic disease that do not have the mutation can then be studied further to determine if there is a second neurologic disease. Please CONTACT US if you think your dog may have DE.

Any information provided to us will be kept strictly confidential.


How can I DNA test my dog for DE?

A DNA test is now available to identify the genetic status of a dog for this gene mutation. The test will determine if the dog has 2 normal copies of the gene (normal or clear), one normal copy and one mutated copy (carrier), or has 2 mutated copies and is at risk to develop clinical signs of DE. Owners of dogs that are suspected to be showing clinical signs of DE will be tested at no charge if they supply the necessary clinical information and submit a blood sample for testing. Dogs that were sampled specifically for this DE research, or have a DNA sample stored at the University of Missouri for any reason (other research, CHIC DNA Bank sent via blood sample, etc) are eligible to request test results at a reduced fee. For owners who sent samples specifically for this DE research, there is no charge to request an email with results only (if a report and certificate is desired, they can be supplied at the reduced fee). This test will be available to order via the OFA website soon (estimated to be available by mid-June or earlier), with DNA collected using a cheek swab and barcoded card. To order, go to www.OFFA.org and click on ORDER DNA TESTS. If a test is desired before ordering through OFA is set up, owners can send a blood sample to the Animal Genetics Lab at the University of Missouri for testing. To request forms and instructions for sending a new sample, or to request a report on a dog with DNA already at MU, please contact Liz Hansen.

Thank you!

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