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Oct. 7, 2013

Targeting canine bloat, a major killer of dogs

A team of Michigan State University veterinary medicine scientists will try to figure out what’s causing canine bloat, one of the biggest – and most mysterious – killers of dogs.

Lead researcher Laura Nelson has been awarded a two-year, $233,774 grant from the American Kennel Club Canine Health Foundation to fund research on the causes of bloat, technically known as gastric dilatation-volvulus.

While the cause is unclear, there is a strong predisposition in some dogs and it is generally thought that bloat is influenced by both genetic and environmental factors. Bloat is one of the leading causes of death in dogs, second only to cancer for some breeds, and the No. 1 killer of Great Danes.

“Not every dog is going to get it,” said Nelson, assistant professor in the MSU College of Veterinary Medicine Department of Small Animal Clinical Sciences. “But there is a strong predisposition in some dogs. Older, nervous, and large and giant dog breeds – particularly Great Danes (and similar deep-chested dogs) – are most prone to bloat. But we still don’t know what causes it. That’s what we want to know – why some dogs get bloat while others don’t.”

When a dog gets bloat, gas fills the stomach, the stomach twists completely around, the gas has no way to escape, and blood and air supply to the stomach are cut off. As the stomach swells, it presses against the abdominal wall and pushes against large blood vessels. Shock is usually the cause of death. The whole progression can happen in a matter of minutes or hours, and surgery is required to save the dog’s life.

Nelson’s team is investigating the relationship of motility – contractions responsible for the digestion of food – with increased bloat risk, and hopes to define the biochemical and genetic alterations that may be associated with hypomotility, abnormally weak contractions.

A new diagnostic tool, SmartPill, makes possible noninvasive assessment of motility. The pill is an ingestible capsule with an instrument inside that measures acidity and pressure. The team will measure the time it takes the capsule to pass through the dog’s system and the pressure spikes along the way.

In addition to investigating gastric motility as a predictor of bloat, researchers will evaluate the expression of the hormones motilin and ghrelin – regulators of gastrointestinal motility – as a predictor of predisposition to bloat. This information will support an investigation of the disease’s genetic foundations.

“The strong breed and familial tendency to bloat points to a strong genetic predisposition to the disease,” said William Horne, chair of the Department of Small Animal Clinical Sciences and co-researcher on the project. “If we can identify a causal gene mutation associated with high risk of GDV, this could lead to developing genetic tests that would allow breeders to make informed breeding decisions.”

In the short term, the research findings may provide clinicians with data that would allow them to make informed decisions about when to use preventative medications or conduct targeted prophylactic surgery – gastropexy – in dogs. This procedure surgically attaches the stomach to the abdominal wall in order to prevent twisting. It is an effective procedure that is well tolerated, but, Nelson notes, is an invasive procedure that may not be necessary in some dogs. There currently is not a good way to determine who to recommend it for.

“There is nothing more frustrating than throwing treatments at something when you don’t understand why it happens,” Nelson said. “With bloat, it happens and you treat it. But it would be so much more satisfying if we really understood why some dogs get bloat and then be able to make more informed treatment decisions and possibly prevent the disease altogether.”

In addition to Nelson and Horne, the research team includes John Fyfe, Joe Hauptman, Kent Refsal, Bryden Stanley, Michele Fritz and James Galligan.