At Cummings School, veterinary researchers are teaming up with scientists at Harvard, MIT and Nestlé Purina PetCare to figure out the genetics of bloat – a common cause of death in big dogs.
Bloat remains a mysterious disease that’s complex to prevent or treat.
The disease develops when a dog’s stomach twists over between its fixed attachments at the esophagus and the upper intestines. This results to the contents of the stomach, containing gas-producing bacteria, to be trapped. Because of this, the stomach swells from the burgeoning gas pressure so much that it eventually crushes a major vein, preventing blood from returning to the heart and often sending the dog into shock.
“Bloat is a challenging disease because it escalates quickly,” says Claire Sharp, a vet at the Foster Hospital for Small Animals. “The dog is fine one minute and in a life-threatening situation the next. Dogs often die from bloat while their owner is off at work or sleeping at night.”
Even a quick diagnosis and emergency surgery to untwist the stomach does not guarantee a dog’s safety.
“Many pets are euthanized because their owners can’t afford an unplanned major operation,” says Sharp. Even with surgery, 10 to 30 percent of dogs with bloat die, she says.
Dog Health Mystery
Bloat most often occurs in large-breeds of dogwith deep-chests, such as German Shepherds, Great Danes, Standard Poodles, and Labrador and Golden Retrievers. This may happen to large mixed breed dogs, too.It may seem like it appears to run in families, but Sharp says no single gene has been identified as the culprit.
The Tufts-led research could give some genetic targets for the first test for bloat. Sharp and Elizabeth Rozanski, a fellow vet, have been awarded a two-year, $250,000 grant from AKC Canine Health Foundation to discover the complex genetics of bloat. The duo will work with researchers at the Broad Institute of Harvard and MIT, who are studying and researching the genetics of purebred dogs to gain insight into how human and canine illnesses develop. They are joined by scientists from Nestlé Purina PetCare who want to understand the effects of nutrition on dog health.
Researchers will try to find out the differences in the genetic makeup of purebred dogs with and without bloat, using blood samples from canine patients at Cummings School and Broad Institute.
Researchers believe that bloat is most likely connected to a dog’s size and form, among other things.
“The ligaments that hold the dog’s stomach in place may be too loose,” Sharp says.
She notes that bloat also seems to happen more often in high-anxiety dogs, probably because they tend to gulp in lots of air when they pant. Vets think that excess air in a dog’s stomach may cause it to twist.
This illness probably involves a variety of genes and environmental and dietary influences “that push the dog over the edge from being highly at risk to actually developing the disease,” she says.
Sharp and Rozanski will also collect blood and abdominal tissue samples from canine patients with and without bloat to distinguish whether specific types or amounts of proteins, hormones, and other molecules in blood and tissues can predict which dogs will get the disease.
“We are confident that a significant amount of risk for bloat will be explained purely by genetics,” and therefore provide data to develop a test for the disease, Sharp says.
There is a genetic test that could determine which dogs are at highest risk of developing bloat. Dogs-at-riskmay undergo preventive surgery known as gastropexy to attach the stomach to the abdominal wall so it cannot twist.
It would also be an amazing breakthrough for the dog-breeding community, says Sharp. “A genetic test would help them dramatically reduce the likelihood of bloat in future offspring.”