Scientists Just Found the Gene Behind Addison's Disease in Nova Scotia Duck Tolling Retrievers

If you see Nova Scotia Duck Tolling Retrievers in your practice, you already know the pattern. Young dog. Addison's disease. Often more than one autoimmune condition. Often fatal within two years despite treatment. It is one of the most heartbreaking presentations in the breed and one of the most clinically frustrating because the underlying cause has, until now, been a black box.

That just changed.

A research team led by Professor Danika Bannasch at the UC Davis School of Veterinary Medicine has identified a gene variant, RESF1, that is strongly associated with Addison's disease in Nova Scotia Duck Tolling Retrievers. The study was published in Scientific Reports on March 12, 2025, and it comes with something immediately actionable: a genetic test is now available through the UC Davis Veterinary Genetics Laboratory to help breeders identify carriers and reduce the frequency of the disease in future generations.

A genetic test is already available. For breeders, this is the most actionable piece of genetic research to come out of toller medicine in years.

Why Tollers Are Hit So Hard

Addison's disease, or hypoadrenocorticism, occurs when the adrenal glands fail to produce adequate amounts of cortisol and aldosterone. In humans, it is understood to be an autoimmune condition where the immune system attacks the adrenal glands. In tollers, the same basic mechanism appears to be at work, but the frequency and severity of the disease in this breed is strikingly high compared to the general dog population.

What makes the toller presentation particularly difficult is that affected dogs typically develop the disease at a young age, and it often does not come alone. Many affected tollers present with multiple autoimmune syndrome, meaning Addison's is accompanied by one or more additional autoimmune conditions hitting simultaneously. That combination is clinically complex and, even with appropriate treatment, dogs with juvenile-onset Addison's disease in this breed typically die within two years.

The disease also appears to be inherited, which is why identifying the underlying genetic mechanism has been such a priority for breed health researchers and why this finding matters so much.

FOR YOUR PRACTICE:  In any toller presenting with lethargy, vomiting, weight loss, or collapse — particularly a young adult — Addison's disease should be high on your differential list. The classic presentation of waxing and waning GI signs in a toller warrants an ACTH stimulation test. Do not wait for the Addisonian crisis to confirm your suspicion.

The Gene: RESF1

The gene variant identified by the UC Davis team is in RESF1. This gene is highly conserved across species, meaning its basic structure and function are very similar in dogs, humans, and other animals. That conservation matters because it suggests the gene plays an important enough biological role that evolution has maintained it across millions of years of divergence.

What makes this finding particularly interesting is that RESF1 has not previously been associated with Addison's disease or multiple autoimmune syndrome in humans. This opens a genuinely new avenue of investigation. The research team suggests that RESF1 should now be explored as a candidate gene for human Addison's disease as well, and that the toller may be a natural model for multiple autoimmune syndrome with relevance not just to veterinary medicine but to human immunology and endocrinology.

The study was led by Bannasch, the Maxine Adler Endowed Chair of Genetics at UC Davis, with graduate students Emily Brown and Scarlett Varney, and included collaborators from UC Davis, the University of Sydney, Uppsala University in Sweden, Genentech, Zoetis, and the University of Prince Edward Island.

RESF1 has not previously been linked to Addison's disease in any species. Tollers may have just given human medicine a new candidate gene to investigate.

The Genetic Test

A genetic test for the RESF1 variant is now available through the UC Davis Veterinary Genetics Laboratory. This is the most immediately actionable part of this research for anyone working with the breed.

For breeders, the test offers the ability to identify carriers and make breeding decisions that reduce the probability of producing affected offspring. Addison's disease in young tollers has caused enormous losses in the breed, and a tool that allows breeders to work proactively against it is significant. The Nova Scotia Duck Tolling Retriever Club of America, which helped fund this research, is already aware of and supporting the availability of the test.

For veterinarians seeing tollers in primary or referral practice, knowing about the test means you can point clients and breeders toward it when the conversation arises. If you have a toller patient with Addison's disease or multiple autoimmune syndrome, genetic testing of the dog and its relatives could be valuable both for the individual family and for the breed population.

TEST AVAILABILITY:  The RESF1 genetic test for Addison's disease in Nova Scotia Duck Tolling Retrievers is available through the UC Davis Veterinary Genetics Laboratory at vgl.ucdavis.edu. Breeders can submit samples directly. Clinicians can reference this resource when counseling toller owners.

The Bigger Picture

It is easy to read a breed-specific genetic finding and file it under 'interesting but narrow.' This one deserves a broader read.

The parallels between canine and human autoimmune disease are not coincidental. Dogs develop autoimmune conditions spontaneously, in complex genetic and environmental contexts, and at rates that make them genuinely useful research models. When a gene variant strongly associated with autoimmune disease in a dog breed turns out to be highly conserved in humans but not yet studied in the context of human autoimmune disease, that is a meaningful finding.

The research team is explicitly calling for RESF1 to be investigated as a human candidate gene. That call is likely to be heard. The toller's contribution to medicine may not end with veterinary genetics.

For now, the practical wins are real. A gene has been identified. A test exists. Breeders have a tool. Veterinarians have a clearer picture of what they are dealing with in these patients. And a breed that has watched too many young dogs die of a condition that seemed inevitable now has a path toward making it less so.

ABOUT THE RESEARCH

This article is adapted from research published March 12, 2025, in Scientific Reports. The study was led by Professor Danika Bannasch, Maxine Adler Endowed Chair of Genetics at the UC Davis School of Veterinary Medicine, with graduate students Emily Brown and Scarlett Varney. Collaborating institutions included the University of Sydney, Uppsala University, Genentech, Zoetis, and the University of Prince Edward Island. Funding was provided by the Nova Scotia Duck Tolling Retriever Club of America, the Canine Health Foundation, the UC Davis Center for Companion Animal Health, the Morris Animal Foundation, and the National Institutes of Health.

TAGS: Addison's Disease  ·  Hypoadrenocorticism  ·  Nova Scotia Duck Tolling Retriever  ·  Canine Genetics  ·  Autoimmune Disease  ·  RESF1  ·  Veterinary Research  ·  Vet Candy