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DENVER/February 18, 2022 – The course of myxomatous mitral valve disease (MMVD), the most common heart problem diagnosed in dogs, is different between Yorkshire terriers and miniature schnauzers. These differences have important implications for diagnosis and prognosis.

That’s the conclusion of a recent research paper published by Morris Animal Foundation-funded researchers from North Carolina State University. The team compared the medical record data of miniature schnauzers and Yorkshire terriers diagnosed with the disease and found important, and previously unreported, differences between the two dog breeds. The team published their findings in the Journal of the American Veterinary Medical Association.

“This study demonstrates that although MMVD is a common heart disease in small-breed dogs, there are key differences between the breeds that are important for veterinarians and pet owners to know about,” said Dr. Kate Meurs, Professor and Interim Dean at North Carolina State University and one of the study’s authors.

The North Carolina State team examined the records of dogs with MMVD and identified 69 miniature schnauzers and 65 Yorkshire terriers that met the inclusion criteria for further study. The team then compared history, physical examination findings and test results to look for differences between the two breeds. They found that although all the dogs had MMVD, there were unexpected differences between the breeds.

“This study shows that some diseases are more complex than previously thought,” said Dr. Janet Patterson-Kane, Morris Animal Foundation Chief Scientific Officer. “Gaining a deeper understanding of MMVD will help veterinarians provide optimized, personalized care for their patients.”

Study results showed that miniature schnauzers were significantly younger at the time of MMVD diagnosis than Yorkshire terriers. The most common clinical sign noted in miniature schnauzers was episodic collapse. In Yorkshire terriers, coughing was the most common sign noted by owners. The complete report can be found on the American Veterinary Medical Association website.

“We don’t have all the answers yet about MMVD,” Meurs said. “But I believe that our results will ultimately impact how we recognize and treat dogs with MMVD.”

The miniature schnauzer and Yorkshire terrier study arose from data collected as part of a grant awarded to Dr. Meurs, through the Foundation’s Mark L. Morris Jr. Investigator Award program. The grant focused on analyzing the genetic makeup of dog breeds at higher risk for MMVD to look for commonalities and differences in the genetic code. The team identified several genes that differed between the breeds as a first step toward a deeper understanding of MMVD.

“Having the Mark Morris Jr. Investigator Award was huge,” Meurs said. “It allowed us to take the time to explore the underlying cause of mitral valve disease across many different dog breeds. The results have pointed us in new experimental directions.”

First awarded in 2016, the Mark L. Morris Jr. Investigator Award was created to honor the legacy and vision of Dr. Mark Morris Jr., son of Dr. Mark Morris Sr., the Foundation’s founder. Mark Morris Jr. was renowned for his pioneering work in small and exotic animal nutrition, and his dedication to Morris Animal Foundation’s mission to advance animal health through excellent science.

About Morris Animal Foundation

Morris Animal Foundation’s mission is to bridge science and resources to advance the health of animals. Founded in 1948 and headquartered in Denver, it is one of the largest nonprofit animal health research organizations in the world, funding more than $142 million in critical studies across a broad range of species. Learn more at