An outbreak of a debilitating and incurable illness in dogs throughout Australia can be linked to Advance Dermocare pet food, a Melbourne University study has found.

Key points: The study found dogs with megaesophagus that ate the food were 437 times more likely to have the disease

The study found dogs with megaesophagus that ate the food were 437 times more likely to have the disease Not all dogs that ate the food were impacted and other factors like breed could be a factor

Not all dogs that ate the food were impacted and other factors like breed could be a factor Researcher says more tests are needed

More than 100 dogs, including dogs from Victoria Police, were struck down during an outbreak of megaesophagus in 2017 and 2018.

The rare condition causes the oesophagus to become enlarged and limits the movement of food and liquid to the animal's stomach.

If dogs survive, they must be fed upright so the food does not get stuck in their oesophagus.

Researchers today released a report which found there was a significant statistical link between Advance Dermocare pet food produced from mid-2017 and a decrease in the number of cases following the voluntary withdrawal of the product throughout Australia in March this year.

U-Vet Hospital director Caroline Mansfield said researchers looked at a sub-set of dogs with megaesophagus and found the odds of them being fed Advance Dermocare in the six months prior to diagnosis were 437 times greater for cases compared to the control group.

"This is an extremely strong association, there is about a one in a million probability that this occurred by chance, supporting the hypothesis that Advance Dermocare was associated with this outbreak of idiopathic megaesophagus in dogs," Associate Professor Mansfield said.

"We suggest that the primary cause of this outbreak of megaesophagus is likely to be multifactorial.

"As not all dogs fed this diet were affected, there may be some individual factors such as breed, predisposition to food intolerance or household factors contributing."

The report noted no single toxin was identified and chronic exposure to or interaction of dietary substances along with the physical characteristics of the dog's food needed to be considered.

Sorry, this video has expired Dogs which survive have to sit upright to eat.

More testing required

Nutritional analysis of Advance Dermocare showed that there were no nutritional excesses.

Tests for standard toxins, including substances associated with neurological disorders or fish content, failed to identify any known toxic concentrations.

Mars Petcare voluntarily recalled Advance Dermocare in March. ( ABC News: Andrew Burch )

"There were some analytes that were higher in the tested diets than in control diets or that were detected but for which there is no known upper safety limit for chronic exposure in humans or dogs," she said.

"The next stage of the investigation will be to see if any of these analytes potentially could have localised effect in the oesophagus."

Professor Mansfield said more extensive laboratory and ingredient testing was required.

Rachel Dola's dog Zara had to be euthanased after getting megaesophagus.

She told the ABC the report confirmed that pet owners were paying "exorbitant prices [for the food] for nothing".

"Mars, having the knowledge of their self-proclaimed state-of-the-art laboratories at the Waltham Centre, either knew the possible problems and still delayed in acting 'till notably close to changing their whole Advance range, or they didn't know and delayed anyway," she said.

"The report states that media coverage likely reduced consumption of the food prior to the recall.

"Our money is better spent on real food."

Elisia Nichol's dog Holly was fed Advance Dermocare and has megaesophagus.

Elisia Nichol's dog Holly sits in her chair to eat next to Thomas. ( Supplied: Elisia Nichol )

"After eight months of looking for answers, we are still looking for the answer," she said.

Ms Nichol said she hoped U-Vet's ongoing investigation would provide more answers.

"Another necessary action is for Mars Petcare to release publicly the results of their own investigation into the outbreak of megaoesophagus," she said.

"At this stage, the proof is in my pet… she has megaoesophagus.

"I want the proof that they actually care about pets and their owners by releasing the report — they need to release the information to safeguard pets and so other manufacturers can ensure risks are minimised."

The company offered pet owners support by reimbursing vet bills for the diagnosis and their animal's ongoing treatment.

A spokeswoman for Mars Petcare said the company remained "deeply concerned" about the number of Australian dogs that consumed Advance Dermocare and were affected by megaesophagus.

"We're disappointed, as we know pet owners will be, that a root cause into the cases of megaoesophagus has yet to be found. We support U-Vet's conclusion that they are likely to be multifactorial," she said.

She said the university's work complemented the company's own investigations, which have not identified a cause to date.

"We want to assure all pet owners that we remain committed to getting to the bottom of what happened," she said.

"Our investigation will continue to explore the interaction of possible cofactors in the development [of] megaoesophagus."

She said Mars Petcare would shortly convene a roundtable of global experts to discuss and scrutinise the occurrence of food-associated megaoesophagus.