Since July 2018, the Food & Drug Administration's Center for Veterinary Medicine (CVM) has taken a multi-pronged approach to investigating reports of dilated cardiomyopathy (DCM) in dogs eating certain pet foods.

Last month, FDA said based on the information gathered as part of its investigation, its advice to pet owners remains consistent. CVM has not identified specific recommendations about dietary changes for dogs who are not displaying DCM symptoms but encouraged pet owners to consult directly with their veterinarians for their animal’s dietary advice.

Between Jan. 1, 2014, and Nov. 30, 2018, FDA received 300 reports of DCM (294 canine reports and six feline reports); 276 of these (273 canine and three feline) were reported after the July 2018 public notification about FDA’s investigation. FDA said while some dog breeds (typically large and giant breeds, plus cocker spaniels) are known to have a genetic predisposition to DCM, the reports continue to span a wide range of breeds -- many that do not have a known genetic predisposition.

In cases in which dogs ate a single primary diet (i.e., didn’t eat multiple food products, excluding treats), 90% reported feeding a grain-free food, FDA said. Approximately 10% reported feeding a food containing grains, and some of these diets were vegan or vegetarian.

A large proportion of the reported diets in DCM cases — both containing grain and grain free — contained peas and/or lentils in various forms (whole, flour, protein, etc.) as a main ingredient (listed within the first 10 ingredients, before vitamins and minerals). The products included commercially available kibble, canned and raw foods, as well as home-cooked diets, FDA said.

Model Doberman genes

Meanwhile, researchers with North Carolina State University and the University of Arizona have identified a gene associated with a common cause of DCM in Doberman pinschers. Their findings could lead to new therapies for both dogs and humans, an announcement from North Carolina State said.

DCM is a fatal genetic heart disorder common in Doberman pinschers. The disease affects the heart muscle’s ability to contract, leading to congestive heart failure or sudden death in adult dogs. Humans with DCM have the same prognosis; existing medical therapies may extend life spans, but a total heart transplant is currently the only effective treatment.

“The severity of this disease means that Doberman breeders and owners are very interested in both preventing it within the population and finding life-extending treatments,” said Kate Meurs, associate dean and director of graduate programs at North Carolina State’s College of Veterinary Medicine and lead author of a paper describing the work. “If we could find a cause, perhaps we could develop better treatments that would not only benefit dogs but extend human lives as well.”

Previously, Meurs had discovered that a mutation in the pyruvate dehydrogenase kinase 4 (PDK4) gene could cause DCM in Dobermans; however, that mutation ended up being associated with a relatively small number of cases, the university said. When Meurs encountered a family of Doberman pinschers with DCM and without the PDK4 variant, she wanted to find the genetic cause of their disease.

Meurs and her colleagues performed whole-genome sequencing on the Doberman family and analyzed their cardiac myofibers — bands of heart muscle — under an electron microscope. The team discovered that another gene, called titin, was the culprit.

“For humans with dilated cardiomyopathy, a titin mutation is the most common cause,” Meurs said. “This gene is responsible for producing one of the largest proteins in both people and dogs and is involved in enabling skeletal and cardiac muscle to contract. This mutation causes cardiac myofibers to stretch out so that the heart muscle cannot do its job properly.”

While titin’s involvement with DCM isn’t a new discovery, finding a mutation in the same gene in Doberman pinschers and people opens up new avenues for possible treatments, the researchers said.

“We now know that the majority of Doberman and human cases of dilated cardiomyopathy are caused by a mutation in titin, which means that not only can breeders now have a reliable test for their dogs but also that we can begin interventionary therapies earlier,” Meurs said. “This means we can now truly test the effectiveness of potential life-extending therapies on these animals."