From lab to leash: Sullivan’s genetic research offers hope for ending dachshunds’ spinal struggles
By Troy Johnson
Dachshund breeders and owners have long faced a painful reality. The beloved breed’s signature short legs can come with an elevated risk of painful and debilitating spinal disease.
Thanks to groundbreaking genetic research by Dr. Stacey Sullivan, professor of practice in neurology and neurosurgery in the Auburn University College of Veterinary Medicine, there may be improved outcomes for the lovable long-bodies. Sullivan’s research shows that dachshunds with fewer copies of the FGF4L2 gene variant – long associated with chondrodystrophy (known to breeders as “CDDY,” the gene responsible for short limb length) – have a dramatically lower risk of developing intervertebral disc disease (IVDD).
“Dachshunds are an incredible breed, and I want to do what I can to help reduce the incidence of disc disease in the breed,” Sullivan said.
Sullivan’s efforts have earned recognition within the canine health community. She was recently named one of eight semifinalists for the American Kennel Club Foundation’s Canine Health Discovery of the Year Award, which recognizes breakthrough research that improves and redefines understanding, prevention and treatment of diseases. A panel of 18 top scientists in canine health reviewed worldwide candidates whose work represents such areas as cancer, nutrition and genetics. Finalists will be revealed in November.
Exploring impact on breeding practices
According to published research, nearly 25 percent of dachshunds will experience back issues during their lifetimes. Signs of symptom onset can include dragging of the back legs, uncoordinated movement in the back legs, whining or yelping when moved or touched, a reluctance to jump or climb and loss of bladder control.
While 85 percent of dachshunds have two copies of the CDDY gene, some inherit one copy (N/CDDY) or no copies at all (N/N). Sullivan and her co-authors found that dachshunds with zero or one copy of CDDY (N/N or N/CDDY) have a significantly lower risk of symptomatic disc disease than dachshunds with two copies of the CDDY gene. These findings have important implications for breeders, who can use the data to identify each dog’s genotype for CDDY and select mates with zero or one copy of CDDY to decrease the risk of disc disease in offspring. The potential result? Healthier dogs, fewer surgeries and less heartbreak for pet owners.
Piecing together a polygenetic puzzle
Sullivan said there are additional research avenues to pursue since disc disease is believed to be polygenetic. “Most dogs with two of the ‘bad’ FGF4L2 genes don’t develop symptoms of disc disease,” said Sullivan, whose lab also explores the genetics of hunting behavior in dachshunds. “It’s important to the dachshund breed that we figure out which of these FGF4L2/FGF4L2 dachshunds that have the healthy spines pass on the as-yet-unidentified ‘good’ genes to their progeny.”
The search for answers includes examination of what other genes impact disc disease risk in dachshunds. Working in collaboration with CVM Professor of Comparative Genomics Xu Wang’s lab, Sullivan intends to establish a dachshund reference genome and identify genes other than CDDY that may influence disc disease risk.
“This will give breeders more genetic tools and hopefully avoid that genetic bottleneck,” Sullivan said, referencing the potential for breeders to select dogs with one or fewer copies of the CDDY gene to the exclusion of all others.
Developing tools to prevent disease
Sullivan’s lab is pursuing development of a phenotype test to screen dachshunds for breeding suitability. The CT-based test could allow screening of puppies, leading to those with degenerated discs to be treated before displaying symptoms through a treatment known as percutaneous disc ablation. Eventually, Sullivan would like to work with the Dachshund Club of America to utilize phenotype and genotype screening to decrease or eliminate disc disease risk in the breed.
Sullivan said it’s not yet known whether the research findings about dachshunds could be applied to other breeds, but her lab is following that line of inquiry with Finnish corgis in collaboration with researchers at the University of Helsinki and the Finnish Kennel Club.
Sullivan’s passion for dachshunds is personal. Her initial contact with dachshunds came through her clinical treatment of hundreds of dogs with IVDD. “From that experience, I came to know and respect the breed,” she said. “After owning several dachshunds that I adopted with medical problems, I eventually purchased a dachshund puppy.”
Born from a show dog line, the puppy also possessed top-notch hunting characteristics. That led to Sullivan entering the world of field and den trials and becoming an AKC field judge for dachshunds, bassets and beagles. Her puppy grew up to become a competitive field dachshund with frequent top 20 national rankings. Sullivan gained perspective on the difficult choices that breeders must make, having bred two litters and produced two additional generations of field champions.
“One recent litter just turned nine months of age,” she said. “Two of the puppies have already finished their field championships, another has field trial placements, and one is training to become a scent-specific trailing police dog.”