Between Jan. 1, 2014, and Nov. 30, 2018, the Food and Drug Administration received reports of 325 cases of dilated cardiomyopathy (DCM) involving dogs, and 10 involving cats, according to an investigation update released Feb. 19. Two of the cats died, as did 74 of the dogs.
In some cases, more than one pet in a household was affected.
In July 2018, FDA announced that it had begun investigating reports of DCM in pets who were fed certain pet foods containing high proportions of peas, lentils, pulses and/or potatoes. Many of the implicated pet foods are advertised as “grain-free.” Most of the reports, 276 out of 300, were received following the FDA’s announcement.
The investigation update does not include data from December 2018 or January 2019, as the partial government shutdown prevented FDA from continuing its investigation during that time period.
DCM is a recognized genetic condition in some dog breeds, including doberman pinschers, great danes, and Irish wolfhounds. It also has been reported in cocker spaniels.
Animals suffering from DCM develop an enlarged heart and may display symptoms such as decreased energy, cough, difficulty breathing and episodes of collapse. If caught early, the condition can be partially reversed with appropriate treatment and diet modifications.
The current spate of DCM reports is not limited to dog breeds known to have a genetic predisposition to the disease, but includes the following breeds, in descending order by frequency of reports: golden retrievers, mixed breed dogs, Labrador retrievers, great danes, Australian shepherds, German shepherds, pit bulls, boxers, doberman pinschers, mastiffs, American cocker spaniels, standard poodles, Shetland sheepdogs, weimaraners, French bulldogs, Australian cattle dogs, Boston terriers, bulldogs, samoyeds, and shih-tsus.
Other breeds with more than one case report include: Afghan hound, beagle, dalmatian, English springer spaniel, flat-coated retriever, unspecified hounds, Maltese, miniature schnauzer, pomeranian, Portuguese water dog, pug, unspecified retriever, Rhodesian ridgeback, rottweiler, saluki, vizsla, and Yorkshire terrier.
Ages of affected dogs range between less than 6 months to 16 years. Dogs suffering from DCM weighed between 8 pounds and 212 pounds. More male dogs than female dogs have been affected.
In contrast, genetically related DCM tends to involve middle-aged to older aged male dogs of large and giant breeds.
The majority of cases reported to FDA, 269 of 325, involved dogs fed dry foods, approximately 90 percent of which were reported to be “grain-free.” Although most of the diets included an animal protein, such as fish, eggs, lamb or chicken, no single source predominated.
Since beginning its investigation, FDA’s Veterinary Laboratory Investigation and Response Network (Vet-LIRN), has tested various products for minerals and metals including calcium, magnesium, phosphorus, iron, cobalt, copper, zinc, selenium and iodine. They also tested for amino acids, including taurine, cysteine and methionine. Cysteine and methionine are required for the body to manufacture taurine.
In addition, Vet-LIRN has tested both grain-free and grain-containing products for protein, fat, moisture, crude fiber, total dietary fiber, soluble fiber, insoluble fiber, total starch, and resistant starch. Grain-free products were higher in fiber and lower in starch than grain-containing products. Otherwise, there was very little difference between the grain-free and grain-containing products.
FDA has received lab reports, diagnostic records such as echocardiograms, and necropsy reports from some of the affected dogs. In addition, the agency is collaborating with Chesapeake Veterinary Cardiology Associates (CVCA) on a prospective study of DCM-diagnosed dogs.
CVCA is collecting medical records, owner interviews, diagnostic samples from each of the diagnosed animals, and is archiving feces and DNA samples for possible future testing.
FDA also has been working with Drs. Lisa Freeman of Tufts University, Joshua Stern of the University of California-Davis, and Darcy Adin of the University of Florida. Stern has been studying the increases in DCM cases in golden retrievers. Many of these cases are associated with taurine deficiency.
The FDA reported it is not aware of similar DCM illness reports or investigations in other countries, according to a spokesperson for the agency, adding that FDA would welcome the opportunity to collaborate with international counterparts on diet-related DCM.
A number of researchers in Canada and the United States, led by W.D. Mansilla of the University of Guelph in Ontario, Canada, recently issued a report on the association between DCM and pulse ingredients in pet food. They suggested L-carnitine deficiency as another possible avenue of investigation into the cause of non-hereditary DCM.
L-carnitine, an amino acid, occurs naturally in animal protein, but is absent from plant protein. It is present at highest concentration in red meats such as lamb and beef, and at a lower level in pork, poultry and fish.
When asked whether FDA was examining the possible effect of L-carnitine on the development of DCM, an agency spokesperson said the agency and its investigative partners “. . . are considering or open to considering any science and evidence-backed theory.”
Guidance to pet owners and veterinarians
If a dog is showing possible signs of DCM or other heart conditions, including decreased energy, cough, difficulty breathing and episodes of collapse, contact your veterinarian as soon as possible. If the symptoms are severe and your veterinarian is not available, you may need to seek emergency veterinary care. Be prepared to provide your veterinarian with a thorough dietary history, including all the foods (including treats) the dog has eaten.
The FDA encourages veterinary professionals to report well-documented cases of DCM in dogs suspected of having a link to diet by using the electronic Safety Reporting Portal or calling their state’s FDA Consumer Complaint Coordinators.
The more information veterinarians provide, particularly feeding history, medical records, and diagnostic testing, the better. Detailed instructions can be found on “How to Report a Pet Food Complaint.” Technical veterinary information that may aid veterinarians can be found in the agency’s Vet-LIRN Update – February 2019.