Pet food products widely available in Canada are being investigated in the U.S. for possible connections to a disease that can be deadly for dogs.

The Food and Drug Administration has received more than 500 complaints about cases of canine dilated cardiomyopathy (DCM) potentially linked to consumption of certain brands of dog food. Although a few of the complaints date back to 2014, the vast majority have come in since the FDA first notified the public about its concerns last summer.

DCM is a disease that makes it difficult for a dog’s heart to pump blood through the rest of its body and can lead to congestive heart failure. Prognoses vary wildly between breeds, but the disease can be fatal.

The exact cause of DCM has not been determined, but researchers at Cornell University say genetic predisposition, infection and diet are all believed to play a role.

Large dogs such as Great Danes, Irish wolfhounds and Doberman pinschers are known to be more likely to develop the disease due to genetic factors. A significant number of DCM complaints have involved golden retrievers, but the FDA says this is likely because of information about the disease spreading through golden retriever-focused social media groups.

The FDA’s investigation has focused on dry dog food as being potentially linked to DCM. The most recent report on the investigation was the first to name specific brands under investigation.

Although the complaints involve dozens of brands of dog food and formula products, there are some common themes. Many of the products under investigation are marketed as being grain-free and contain significant amounts of peas, lentils, pulses and potatoes.

The dog food brand that showed up most often in the complaints – 67 times – was Acana, which is manufactured by Edmonton-based Champion Pet Foods. Orijen, another Champion brand, was named in 12 complaints.

No similar investigation has been launched by Canadian authorities because pet food is not regulated in Canada, a spokesperson for the Canadian Food Inspection Agency told CTVNews.ca.

Champion said in a statement that it takes DCM-related concerns seriously and is working with industry leaders to conduct further research into the causes of the disease.

“Our own research, and the millions of pets who have thrived by eating our food over 25 years, have shown that Champion pet foods are safe,” the statement reads.

Two other brands of dog food were named in more than 50 of the complaints: Zignature and Taste of the Wild. Both are produced in the U.S. but widely available in Canadian pet stores. The manufacturers of each have issued similar statements to Champion’s, pointing to the results of favourable research and affirming commitments to food safety.

A dozen other brands – all American – have been the subject of at least 10 complaints: 4Health, Earthborn Holistic, Blue Buffalo, Nature’s Domain, Fromm, Merrick, California Natural, Natural Balance, Nature’s Variety, NutriSource, Nutro and Rachael Ray Nutrish. California Natural has been discontinued, but the rest are all available in Canada through retail and/or online sales.

No recalls have been issued for any of the listed dog foods, because it has not yet been determined if there is in fact a connection between any of them and DCM. Testing has taken place on the foods in question and some of the dogs that developed DCM, but no conclusive results have been found.

The FDA says there is no reason for pet owners to stop using any specific dog foods at this point, although they recommend conversations with veterinarians about any dietary concerns and immediate care for any dogs that show signs of lethargy, difficulty breathing, cough or collapse.

The 524 complaints received by the FDA about DCM cover 560 dogs and 14 cats.